2022-12-15 17:52:00

author: Hans Hagen <pragma@wxs.nl> 2022-12-15 19:13:44 +0100
committer: Context Git Mirror Bot <phg@phi-gamma.net> 2022-12-15 19:13:44 +0100
commit: 8f472c629a996f1c08281198210354a253d7f56b (patch)
tree: 26f5fa0bda520d7ea9e87947df6978b9085a7d58 /tex
parent: 3bdc9b9072bba774cd5c604fe185d39ddbdc911e (diff)
download: context-8f472c629a996f1c08281198210354a253d7f56b.tar.gz
160 files changed, 1795 insertions, 1506 deletions
diff --git a/tex/context/base/mkii/cont-new.mkii b/tex/context/base/mkii/cont-new.mkii
index 9bd797523..b557f5666 100644
--- a/tex/context/base/mkii/cont-new.mkii
+++ b/tex/context/base/mkii/cont-new.mkii
@@ -11,7 +11,7 @@
 %C therefore copyrighted by \PRAGMA. See mreadme.pdf for
 %C details.
 
-\newcontextversion{2022.12.09 16:31}
+\newcontextversion{2022.12.15 17:49}
 
 %D This file is loaded at runtime, thereby providing an
 %D excellent place for hacks, patches, extensions and new
diff --git a/tex/context/base/mkii/context.mkii b/tex/context/base/mkii/context.mkii
index 3a7b24584..1c6f24507 100644
--- a/tex/context/base/mkii/context.mkii
+++ b/tex/context/base/mkii/context.mkii
@@ -20,7 +20,7 @@
 %D your styles an modules.
 
 \edef\contextformat {\jobname}
-\edef\contextversion{2022.12.09 16:31}
+\edef\contextversion{2022.12.15 17:49}
 
 %D For those who want to use this:
 
diff --git a/tex/context/base/mkiv/cont-new.mkiv b/tex/context/base/mkiv/cont-new.mkiv
index 3c2193719..ac24c71a5 100644
--- a/tex/context/base/mkiv/cont-new.mkiv
+++ b/tex/context/base/mkiv/cont-new.mkiv
@@ -13,7 +13,7 @@
 
 % \normalend % uncomment this to get the real base runtime
 
-\newcontextversion{2022.12.09 16:31}
+\newcontextversion{2022.12.15 17:49}
 
 %D This file is loaded at runtime, thereby providing an excellent place for hacks,
 %D patches, extensions and new features. There can be local overloads in cont-loc
diff --git a/tex/context/base/mkiv/context.mkiv b/tex/context/base/mkiv/context.mkiv
index b89cecdfe..2e915c2a4 100644
--- a/tex/context/base/mkiv/context.mkiv
+++ b/tex/context/base/mkiv/context.mkiv
@@ -49,7 +49,7 @@
 %D {YYYY.MM.DD HH:MM} format.
 
 \edef\contextformat {\jobname}
-\edef\contextversion{2022.12.09 16:31}
+\edef\contextversion{2022.12.15 17:49}
 
 %D Kind of special:
 
diff --git a/tex/context/base/mkiv/mult-fmt.lua b/tex/context/base/mkiv/mult-fmt.lua
index 67133aab2..bbcdfd343 100644
--- a/tex/context/base/mkiv/mult-fmt.lua
+++ b/tex/context/base/mkiv/mult-fmt.lua
@@ -217,9 +217,9 @@ function interfaces.setuserinterface(interface,response)
                 constant = constant[interface] or constant.en or given
                 constants[constant] = given -- breedte -> width
                 nofconstants = nofconstants + 1
-                setmacro("c!" .. given,given,"immutable")
+                setmacro("c!" .. given,given,"immutable","constant")
                 if reversetoo then
-                    setmacro("k!" .. constant,given,"immutable")
+                    setmacro("k!" .. constant,given,"immutable","constant")
                 end
                 report_constant("%-40s: %s",given,constant)
             end
@@ -232,7 +232,7 @@ function interfaces.setuserinterface(interface,response)
                 variable = variable[interface] or variable.en or given
                 variables[given] = variable -- ja -> yes
                 nofvariables = nofvariables + 1
-                setmacro("v!" .. given,variable,"immutable")
+                setmacro("v!" .. given,variable,"immutable","constant")
                 report_variable("%-40s: %s",given,variable)
             end
             logs.stopfilelogging()
@@ -244,7 +244,7 @@ function interfaces.setuserinterface(interface,response)
                 element = element[interface] or element.en or given
                 elements[element] = given
                 nofelements = nofelements + 1
-                setmacro("e!" .. given,element,"immutable")
+                setmacro("e!" .. given,element,"immutable","constant")
                 report_element("%-40s: %s",given,element)
             end
             logs.stopfilelogging()
diff --git a/tex/context/base/mkiv/mult-low.lua b/tex/context/base/mkiv/mult-low.lua
index 835588e46..d213bf7d7 100644
--- a/tex/context/base/mkiv/mult-low.lua
+++ b/tex/context/base/mkiv/mult-low.lua
@@ -436,7 +436,8 @@ return {
         --
         "getparameters", "geteparameters", "getgparameters", "getxparameters", "forgetparameters", "copyparameters",
         --
-        "getdummyparameters", "dummyparameter", "directdummyparameter", "setdummyparameter", "letdummyparameter", "setexpandeddummyparameter",
+        "getdummyparameters", "dummyparameter", "directdummyparameter", "setdummyparameter", "letdummyparameter",
+        "setexpandeddummyparameter", "resetdummyparameter",
         "usedummystyleandcolor", "usedummystyleparameter", "usedummycolorparameter",
         --
         "processcommalist", "processcommacommand", "quitcommalist", "quitprevcommalist",
diff --git a/tex/context/base/mkiv/mult-prm.lua b/tex/context/base/mkiv/mult-prm.lua
index 891b795ad..2a73d765b 100644
--- a/tex/context/base/mkiv/mult-prm.lua
+++ b/tex/context/base/mkiv/mult-prm.lua
@@ -298,8 +298,11 @@ return {
   "boxymove",
   "boxyoffset",
   "catcodetable",
+  "cdef",
+  "cdefcsname",
   "cfcode",
   "clearmarks",
+  "constant",
   "copymathatomrule",
   "copymathparent",
   "copymathspacing",
@@ -640,6 +643,7 @@ return {
   "tracinghyphenation",
   "tracinginserts",
   "tracinglevels",
+  "tracinglists",
   "tracingmarks",
   "tracingmath",
   "tracingnodes",
diff --git a/tex/context/base/mkiv/status-files.pdf b/tex/context/base/mkiv/status-files.pdf
index 93a9c8822..8f7009b07 100644
--- a/tex/context/base/mkiv/status-files.pdf
+++ b/tex/context/base/mkiv/status-files.pdf
diff --git a/tex/context/base/mkiv/status-lua.pdf b/tex/context/base/mkiv/status-lua.pdf
index 089aadf1a..36e22cc39 100644
--- a/tex/context/base/mkiv/status-lua.pdf
+++ b/tex/context/base/mkiv/status-lua.pdf
diff --git a/tex/context/base/mkxl/anch-bck.mklx b/tex/context/base/mkxl/anch-bck.mklx
index 818fade98..2eeebd547 100644
--- a/tex/context/base/mkxl/anch-bck.mklx
+++ b/tex/context/base/mkxl/anch-bck.mklx
@@ -637,7 +637,7 @@
     if nofposboxes = 1 :
         posboxes[1] := (posboxes[1] enlarged mpvar "lineoffset") cornered mpvar "lineoffset" ;
         fill posboxes[1] withcolor mpvar "fillcolor" ;
-        draw posboxes[1] withpen pencircle scaled mpvar "linewidth"  withcolor mpvar "linecolor"  ;
+        draw posboxes[1] withpen pencircle scaled mpvar "linewidth" withcolor mpvar "linecolor"  ;
     fi ;
 \stopMPpositiongraphic
 
diff --git a/tex/context/base/mkxl/anch-box.mkxl b/tex/context/base/mkxl/anch-box.mkxl
index 02cdf5fb8..9885123c2 100644
--- a/tex/context/base/mkxl/anch-box.mkxl
+++ b/tex/context/base/mkxl/anch-box.mkxl
@@ -42,7 +42,6 @@
 %         linecolor=\namedboxanchorcontentparameter{#1}{\c!rulecolor}}%
 %    \stoppositionoverlay
 %    \endgroup}
-
 \tolerant\permanent\protected\def\connectboxanchors[#1]#*[#2]#*[#3]#*[#4]#*#:#5#6%
   {\begingroup
    %
@@ -70,17 +69,40 @@
        \setMPpositiongraphic
          {\boxanchorposone}%
          {\namedboxanchorcontentparameter{#1}\c!mp}%
-         {from=\boxanchorposone,%
+         {span=no,
+          from=\boxanchorposone,%
           to=\boxanchorpostwo,%
-          distance={\namedboxanchorcontentparameter{#1}\c!distance},%
+        % distance={\namedboxanchorcontentparameter{#1}\c!distance},%
           dashtype={\namedboxanchorcontentparameter{#1}\c!dash},%
-          arrow={\namedboxanchorcontentparameter{#1}\c!arrow},%
-          alternative={\namedboxanchorcontentparameter{#1}\c!alternative},%
-          text={\namedboxanchorcontentparameter{#1}\c!text},%
-          rulethickness={\namedboxanchorcontentparameter{#1}\c!rulethickness},%
-          linecolor=\namedboxanchorcontentparameter{#1}{\c!rulecolor}}%
+        % arrow={\namedboxanchorcontentparameter{#1}\c!arrow},%
+        % alternative={\namedboxanchorcontentparameter{#1}\c!alternative},%
+        % text={\namedboxanchorcontentparameter{#1}\c!text},%
+        % rulethickness={\namedboxanchorcontentparameter{#1}\c!rulethickness},%
+          linecolor=\namedboxanchorcontentparameter{#1}{\c!rulecolor},
+          #3}%
+       %
      \stoppositionoverlay
    }%
+   \ifcstok{\namedboxanchorcontentparameter{#1}\c!page}\v!yes
+     \normalexpanded{%
+       \startpositionoverlay{text+1}% will become configurable region
+           \setMPpositiongraphic
+             {\boxanchorpostwo}%
+             {\namedboxanchorcontentparameter{#1}\c!mp}%
+             {span=yes,
+              from=\boxanchorposone,%
+              to=\boxanchorpostwo,%
+            % distance={\namedboxanchorcontentparameter{#1}\c!distance},%
+              dashtype={\namedboxanchorcontentparameter{#1}\c!dash},%
+            % arrow={\namedboxanchorcontentparameter{#1}\c!arrow},%
+            % alternative={\namedboxanchorcontentparameter{#1}\c!alternative},%
+            % text={\namedboxanchorcontentparameter{#1}\c!text},%
+            % rulethickness={\namedboxanchorcontentparameter{#1}\c!rulethickness},%
+              linecolor=\namedboxanchorcontentparameter{#1}{\c!rulecolor}%
+              #3}%
+       \stoppositionoverlay
+     }%
+   \fi
    \endgroup}
 
 % dedicated or not
@@ -120,7 +142,7 @@
    \stoppositionoverlay
    \endgroup}
 
-\let\m_anch_matrix_list\empty
+\lettonothing\m_anch_matrix_list
 
 \tolerant\permanent\protected\def\startmatrixanchors
   {\glet\m_anch_matrix_list\empty
diff --git a/tex/context/base/mkxl/anch-pgr.mkxl b/tex/context/base/mkxl/anch-pgr.mkxl
index 4ffedbfc3..5071f16d5 100644
--- a/tex/context/base/mkxl/anch-pgr.mkxl
+++ b/tex/context/base/mkxl/anch-pgr.mkxl
@@ -204,13 +204,13 @@
 %D
 %D \typebuffer[graphic]
 
-\immutable\def\MPanchoridentifier{mpa}  % {mp-anchor}
-\mutable  \def\MPanchornumber    {\the\realpageno}
-\mutable  \let\MPanchorid        \empty
+\immutable\def         \MPanchoridentifier{mpa}  % {mp-anchor}
+\mutable  \def         \MPanchornumber    {\the\realpageno}
+\mutable  \lettonothing\MPanchorid
 
 %D The rest of the definitions concerning such overlays may look complicated,
 
-\mutable\let\currentpositionoverlay\empty
+\mutable\lettonothing\currentpositionoverlay
 
 %D Position actions are automatically executed when a position is set.
 
@@ -256,7 +256,7 @@
      \expandafter\gobbletwoarguments
    \fi}
 
-\let\currentpositionregion\empty
+\lettonothing\currentpositionregion
 
 \def\anch_positions_region_overlay_indeed#1#2%
   {\begingroup
@@ -294,14 +294,14 @@
 
 \ifdefined\checkpositionoverlays \else \let\checkpositionoverlays\relax \fi
 
-\mutable\let\currentpositionoverlay\empty
+\mutable\lettonothing\currentpositionoverlay
 
 \def\anch_positions_overlay_start_yes#1%
   {\checkpositionoverlays
    \edef\currentpositionoverlay{#1}}
 
 \permanent\protected\def\stoppositionoverlay
-  {\let\currentpositionoverlay\empty}
+  {\lettonothing\currentpositionoverlay}
 
 %D A position graphic is a normal (non||reused) \METAPOST\ graphic, used
 %D immediately, with zero dimensions, so that a sequence of them does not harm.
diff --git a/tex/context/base/mkxl/anch-pos.mkxl b/tex/context/base/mkxl/anch-pos.mkxl
index f8891eb33..75e8f87d7 100644
--- a/tex/context/base/mkxl/anch-pos.mkxl
+++ b/tex/context/base/mkxl/anch-pos.mkxl
@@ -55,10 +55,10 @@
 % see top: \newbox\b_anch_position
 % see top: \newif \ifpositioning   % sort of public
 
-\mutable\let\currentposition      \empty
-\mutable\let\currentpositionaction\empty
-\mutable\let\currentpositionanchor\empty
-\mutable\let\currentpositionregion\empty
+\mutable\lettonothing\currentposition
+\mutable\lettonothing\currentpositionaction
+\mutable\lettonothing\currentpositionanchor
+\mutable\lettonothing\currentpositionregion
 
 %D Sometimes we want to trick the position handler a bit:
 
diff --git a/tex/context/base/mkxl/anch-tab.mkxl b/tex/context/base/mkxl/anch-tab.mkxl
index 11e9598d9..1c89666dc 100644
--- a/tex/context/base/mkxl/anch-tab.mkxl
+++ b/tex/context/base/mkxl/anch-tab.mkxl
@@ -227,9 +227,9 @@
 %D In order to prevent potential clashes with abbreviations, postpone the mapping and
 %D make them mutable.
 
-\mutable\let\GSC\empty
-\mutable\let\GFC\empty
-\mutable\let\GTC\empty
+\mutable\lettonothing\GSC
+\mutable\lettonothing\GFC
+\mutable\lettonothing\GTC
 
 \appendtoks
     \enforced\let\GSC\tbGSC
diff --git a/tex/context/base/mkxl/attr-lay.mkxl b/tex/context/base/mkxl/attr-lay.mkxl
index 00c633533..122839c06 100644
--- a/tex/context/base/mkxl/attr-lay.mkxl
+++ b/tex/context/base/mkxl/attr-lay.mkxl
@@ -66,14 +66,14 @@
 \def\currentviewerlayer{\the\currentviewerlayertoks}
 
 \appendtoks
-    \let\currentviewerlayer\empty
+    \lettonothing\currentviewerlayer
 \to \everybeforepagebody
 
 % layout components are implemented rather directly (speed)
 
 \installcorenamespace{layoutcomponentattribute}
 
-\mutable\let\layoutcomponentboxattribute\empty
+\mutable\lettonothing\layoutcomponentboxattribute
 
 \permanent\def\attr_layoutcomponent_initialize#1%
   {\edef\layoutcomponentboxattribute{\clf_definedlayoutcomponent{#1}}%
@@ -87,11 +87,11 @@
    \fi}
 
 \permanent\def\attr_layoutcomponent_reset
-  {\let\layoutcomponentboxattribute\empty}
+  {\lettonothing\layoutcomponentboxattribute}
 
-\permanent\let\setlayoutcomponentattribute  \gobbleoneargument
-\permanent\let\resetlayoutcomponentattribute\relax
-          \let\layoutcomponentboxattribute  \empty
+\permanent\let         \setlayoutcomponentattribute  \gobbleoneargument
+\permanent\let         \resetlayoutcomponentattribute\relax
+          \lettonothing\layoutcomponentboxattribute
 
 \permanent\protected\def\showlayoutcomponents
   {\enforced\let\setlayoutcomponentattribute  \attr_layoutcomponent_set
diff --git a/tex/context/base/mkxl/back-exp.mkxl b/tex/context/base/mkxl/back-exp.mkxl
index 82329cc6a..3c8c23c59 100644
--- a/tex/context/base/mkxl/back-exp.mkxl
+++ b/tex/context/base/mkxl/back-exp.mkxl
@@ -312,7 +312,7 @@
 
 \permanent\protected\def\dostartexport
   {%\glet\dostartexport\relax
-   \let\currentexport\empty
+   \lettonothing\currentexport
    \clf_setupexport
        align      {\exportparameter\c!align}%
        bodyfont   \dimexpr\exportparameter\c!bodyfont\relax
diff --git a/tex/context/base/mkxl/bibl-bib.mkxl b/tex/context/base/mkxl/bibl-bib.mkxl
index cc916b329..d8ab26d28 100644
--- a/tex/context/base/mkxl/bibl-bib.mkxl
+++ b/tex/context/base/mkxl/bibl-bib.mkxl
@@ -450,7 +450,7 @@
      \edef\bibtexpublicationsalternative{\@@pbalternative}% parent
      \ifempty\bibtexpublicationsalternative \else
        \processcommacommand[\bibtexpublicationsalternative]\dodoloadbibtexpublicationalternative
-       \let\@@pbalternative\empty
+       \lettonothing\@@pbalternative
      \fi
    \fi}
 
@@ -655,9 +655,9 @@
      {\global\advance\bibtexcounter\plusone
       \ctxlua{bibtex.hacks.registerplaced("\currentbibtexsessiontag")}%
       \let\currentlist\currentbibtexsession
-      \let\currentlistentrynumber    \bibtexcounter
-      \let\currentlistentrytitle     \thebibtexpublicationlistelement
-      \let\currentlistentrypagenumber\empty
+      \let\currentlistentrynumber\bibtexcounter
+      \let\currentlistentrytitle\thebibtexpublicationlistelement
+      \lettonothing\currentlistentrypagenumber
       \strc_lists_apply_renderingsetup}
      {}} % invalid
 
diff --git a/tex/context/base/mkxl/bibl-tra.mkxl b/tex/context/base/mkxl/bibl-tra.mkxl
index c84d0878e..fc21724b3 100644
--- a/tex/context/base/mkxl/bibl-tra.mkxl
+++ b/tex/context/base/mkxl/bibl-tra.mkxl
@@ -258,7 +258,7 @@
   {\dosingleempty\dosetupbibtex}
 
 \protected\def\dosetupbibtex[#1]%
-  {\let\@@pbdatabase\empty
+  {\lettonothing\@@pbdatabase
    \getparameters[\??pb][#1]%
    \the\everysetupbibtex}
 
@@ -299,7 +299,7 @@
      {\readsysfile{bibl-\@@pbalternative.tex}
         {\showmessage\m!publications{6}{bibl-\@@pbalternative}}
         {\showmessage\m!publications{1}{bibl-\@@pbalternative}}%
-      \let\@@pbalternative\empty}%
+      \lettonothing\@@pbalternative}%
    \let\setuppublicationlayout\normalsetuppublicationlayout % overloaded in bibl-num ... vadjust needs to be done with option
    \getparameters[\??pb][#1]% as bibl-* can have set things back
    \the\everysetuppublications
@@ -537,7 +537,7 @@
      \fi
      \ifnum\todocounter>\zerocount
        % find the current author list
-       \let\templist\empty
+       \lettonothing\templist
        \dorecurse{#2}
          {\scratchtoks\doubleexpandafter{\csname\??pb @#1\recurselevel\endcsname}%
           \edef\templist{\ifempty\templist\else\templist,\fi\the\scratchtoks}}%
@@ -881,10 +881,10 @@
      {\global\advance\bibtexcounter\plusone
       \def\currentpublicationkey{#1}%
       \ctxlua{bibtex.hacks.registerplaced("#1")}%
-      \def \currentlist               {pubs}%
-      \edef\currentlistentrynumber    {\number\bibtexcounter}%
-      \let \currentlistentrytitle     \bibtexpubtext
-      \let \currentlistentrypagenumber\empty
+      \def\currentlist{pubs}%
+      \edef\currentlistentrynumber{\number\bibtexcounter}%
+      \let\currentlistentrytitle\bibtexpubtext
+      \lettonothing\currentlistentrypagenumber
       \strc_lists_apply_renderingsetup}
      {}} % invalid
 
@@ -897,7 +897,7 @@
    \the\initializebibdefinitions % NEW
    \def\@@currentalternative{:l:}%
    \presetbibvariables
-   \let\biblanguage\empty
+   \lettonothing\biblanguage
    \ignorespaces
    \bibgetvard{#1}%
    \removeunwantedspaces
@@ -963,9 +963,9 @@
       \ifempty\LOextras
         \setupcite[\@@currentalternative][#1]%
       \else
-        \expandafter\ifrelax\csname \??pv \@@currentalternative\c!right\endcsname
+        \expandafter\ifrelax\csname\??pv\@@currentalternative\c!right\endcsname
           % avoids tail recursion
-          \expandafter\let\csname \??pv \@@currentalternative\c!right\endcsname\empty
+          \expandafter\lettonothing\csname\??pv\@@currentalternative\c!right\endcsname
         \fi
         \expandafter\ifrelax\csname LOright\endcsname
           \edef\LOextras{{\LOextras\bibalternative\c!right}}%
@@ -1050,22 +1050,22 @@
 
 %D Delegate this to \LUA.
 
-% \let\ixlastcommand   \relax
-% \let\ixsecondcomman  \relax
-% \let\ixfirstcommand  \relax
-% \let\thebibauthors   \empty
-% \let\thebibyears     \empty
-% \let\authorcount     \!!zerocount
+% \let         \ixlastcommand \relax
+% \let         \ixsecondcomman\relax
+% \let         \ixfirstcommand\relax
+% \lettonothing\thebibauthors
+% \lettonothing\thebibyears
+% \let         \authorcount   \!!zerocount
 
-\let\currentbibauthor\empty
+\lettonothing\currentbibauthor
 
 \protected\def\ixbibauthoryear#1#2#3#4%
   {\bgroup
-   \gdef\ixlastcommand  {#4}%
+   \gdef\ixlastcommand{#4}%
    \gdef\ixsecondcommand{#3}%
-   \gdef\ixfirstcommand {#2}%
-   \glet\thebibauthors  \empty
-   \glet\thebibyears    \empty
+   \gdef\ixfirstcommand{#2}%
+   \glettonothing\thebibauthors
+   \glettonothing\thebibyears
    \getcommalistsize[#1]%
    \ifbibcitecompress
      \dorecurse\commalistsize{\xdef\thebibyears{\thebibyears,}}%
@@ -1105,7 +1105,7 @@
   {\getcommacommandsize[#1]%
    \ifcase\commalistsize
     % anonymous?
-     \let\currentbibauthor\empty
+     \lettonothing\currentbibauthor
    \or
      \def\currentbibauthor{#1}%
    \or
@@ -1118,7 +1118,7 @@
 
 \protected\def\handlemultiplebibauthors#1#2%
   {\citescratchcounter\zerocount
-   \let\currentbibauthor\empty
+   \lettonothing\currentbibauthor
    \protected\def\bibprocessauthoritem##1%
      {\advance\citescratchcounter\plusone
       \ifnum \citescratchcounter=#1\relax
diff --git a/tex/context/base/mkxl/buff-ini.mkxl b/tex/context/base/mkxl/buff-ini.mkxl
index c6aa6de3f..d561841ff 100644
--- a/tex/context/base/mkxl/buff-ini.mkxl
+++ b/tex/context/base/mkxl/buff-ini.mkxl
@@ -22,7 +22,7 @@
 %D pretty and never be efficient but it has served us for ages (conceptually it's
 %D as in \MKII).
 
-\mutable\let\currentbuffer\empty
+\mutable\lettonothing\currentbuffer
 
 % \doifelsebuffer      {#1} % expandable
 % \doifelsebufferempty {#1} % non expandable
diff --git a/tex/context/base/mkxl/buff-par.mklx b/tex/context/base/mkxl/buff-par.mklx
index b6ffa3f53..63e6f47bd 100644
--- a/tex/context/base/mkxl/buff-par.mklx
+++ b/tex/context/base/mkxl/buff-par.mklx
@@ -131,11 +131,11 @@
    \relax
    \endgroup}
 
-\mutable\let\currentparallelinstance\empty
-\mutable\let\currentparallelnumber  \empty
-\mutable\let\currentparallelline    \empty
-\mutable\let\currentparallellabel   \empty
-\mutable\let\currentparallelcontent \empty
+\mutable\lettonothing\currentparallelinstance
+\mutable\lettonothing\currentparallelnumber
+\mutable\lettonothing\currentparallelline
+\mutable\lettonothing\currentparallellabel
+\mutable\lettonothing\currentparallelcontent
 
 \permanent\protected\def\doflushparallel#instance#status#line#label#content% called at lua end
   {\begingroup
diff --git a/tex/context/base/mkxl/buff-ver.mkxl b/tex/context/base/mkxl/buff-ver.mkxl
index ec7ef5fc3..6fef148f1 100644
--- a/tex/context/base/mkxl/buff-ver.mkxl
+++ b/tex/context/base/mkxl/buff-ver.mkxl
@@ -582,7 +582,7 @@
 
 % [category] [settings] {name} % for historic reasons, all filenames are {}
 
-\mutable\let\currenttypingfile\empty
+\mutable\lettonothing\currenttypingfile
 
 \appendtoks
     \frozen\protected\instance\edefcsname\e!type\currenttyping\v!file\endcsname{\typefile[\currenttyping]}%
@@ -846,7 +846,7 @@
   {\dontleavehmode
    \begingroup
    \enforced\let\setupcurrenttyping\setupcurrenttype % a terrible hack but it saves code
-   \let\currenttype\empty
+   \lettonothing\currenttype
    \ifparameters
      \buff_verbatim_type_buffer_indeed_inline\currenttyping\empty% []
    \or
diff --git a/tex/context/base/mkxl/catc-ini.mkxl b/tex/context/base/mkxl/catc-ini.mkxl
index 0740e7e2a..6e40ca822 100644
--- a/tex/context/base/mkxl/catc-ini.mkxl
+++ b/tex/context/base/mkxl/catc-ini.mkxl
@@ -319,9 +319,9 @@
      -%
    \fi}
 
-\let\syst_catcodes_trace_set \empty
-\let\syst_catcodes_trace_push\empty
-\let\syst_catcodes_trace_pop \empty
+\lettonothing\syst_catcodes_trace_set
+\lettonothing\syst_catcodes_trace_push
+\lettonothing\syst_catcodes_trace_pop
 
 % \tracecatcodetables
 
diff --git a/tex/context/base/mkxl/chem-str.mkxl b/tex/context/base/mkxl/chem-str.mkxl
index 6c591225e..5f3f8b6c7 100644
--- a/tex/context/base/mkxl/chem-str.mkxl
+++ b/tex/context/base/mkxl/chem-str.mkxl
@@ -82,7 +82,7 @@
   [\c!align=\v!normal,
    \c!strut=\v!no]
 
-\mutable\let\currentdefinedchemical\empty
+\mutable\lettonothing\currentdefinedchemical
 
 \permanent\protected\def\setupchemicalframed
   {\setupframed[\??chemicalframed]}
@@ -120,9 +120,9 @@
       \ifcase\currentxfontsize\or\scriptstyle\or\scriptscriptstyle\fi
       #1}}
 
-\setvalue{\??chemicalsize\v!small }{\txx}
-\setvalue{\??chemicalsize\v!medium}{\tx}
-\setvalue{\??chemicalsize\v!big   }{}
+\defcsname\??chemicalsize\v!small \endcsname{\txx}
+\defcsname\??chemicalsize\v!medium\endcsname{\tx}
+\defcsname\??chemicalsize\v!big   \endcsname{}
 
 \newtoks       \everychemical
 \newtoks       \everystructurechemical
@@ -256,14 +256,14 @@
 \permanent\protected\def\chemicalbottext#1{\global\settrue\c_chem_some_text\gdef\m_chem_bot_text{#1}\ignorespaces}
 \permanent\protected\def\chemicalmidtext#1{\global\settrue\c_chem_some_text\gdef\m_chem_mid_text{#1}\ignorespaces}
 
-\mutable\let\toptext\empty
-\mutable\let\bottext\empty
-\mutable\let\midtext\empty
+\mutable\lettonothing\toptext
+\mutable\lettonothing\bottext
+\mutable\lettonothing\midtext
 
 \appendtoks
-    \let\toptext\chemicaltoptext \glet\m_chem_top_text\empty
-    \let\bottext\chemicalbottext \glet\m_chem_bot_text\empty
-    \let\midtext\chemicalmidtext \glet\m_chem_mid_text\empty
+    \let\toptext\chemicaltoptext \glettonothing\m_chem_top_text
+    \let\bottext\chemicalbottext \glettonothing\m_chem_bot_text
+    \let\midtext\chemicalmidtext \glettonothing\m_chem_mid_text
     \global\setfalse\c_chem_some_text
 \to \everystructurechemical
 
diff --git a/tex/context/base/mkxl/colo-ext.mkxl b/tex/context/base/mkxl/colo-ext.mkxl
index d4747ae94..f3779bb58 100644
--- a/tex/context/base/mkxl/colo-ext.mkxl
+++ b/tex/context/base/mkxl/colo-ext.mkxl
@@ -80,7 +80,7 @@
     \colo_intents_set_text
 \to \everysetupcolors
 
-\let\p_colo_intent\empty
+\lettonothing\p_colo_intent
 
 \def\colo_intents_set_text
   {\edef\p_colo_intent{\colorsparameter\c!intent}%
diff --git a/tex/context/base/mkxl/colo-ini.mkxl b/tex/context/base/mkxl/colo-ini.mkxl
index f7909e2a3..68aba39ab 100644
--- a/tex/context/base/mkxl/colo-ini.mkxl
+++ b/tex/context/base/mkxl/colo-ini.mkxl
@@ -61,10 +61,10 @@
 
 \let\m_colo_weight_gray\v!yes
 
-\mutable\let\currentcolormodel \empty
-\mutable\let\currentcolorname  \empty
-\mutable\let\currentcolorpalet \empty
-\mutable\let\currentcolorprefix\empty % \currentcolorpalet:
+\mutable\lettonothing\currentcolormodel
+\mutable\lettonothing\currentcolorname
+\mutable\lettonothing\currentcolorpalet
+\mutable\lettonothing\currentcolorprefix % \currentcolorpalet:
 
 %D \macros
 %D   {definecolor,defineglobalcolor,definenamedcolor,definespotcolor,definemultitonecolor,
@@ -490,8 +490,8 @@
      \expandafter\secondoftwoarguments
    \fi}
 
-\mutable\let\paletlist\empty
-\mutable\let\paletsize\!!zerocount
+\mutable\lettonothing\paletlist
+\mutable\let         \paletsize\!!zerocount
 
 \permanent\protected\def\getpaletlist[#1]%
   {\edef\paletlist{\begincsname\??paletlist#1\endcsname}}
@@ -588,15 +588,15 @@
   {\edef\currentcolorpalet{#1}%
    \ifempty\currentcolorpalet
      % seems to be a reset
-     \let\currentcolorprefix\empty
+     \lettonothing\currentcolorprefix
     %\t_colo_prefix\emptytoks
    \orelse\ifcsname\??paletlist\currentcolorpalet\endcsname
      \edef\currentcolorprefix{#1:}%
     %\t_colo_prefix\expandafter{\currentcolorprefix}%
    \else
      \colo_helpers_show_message\m!colors7\currentcolorpalet
-     \let\currentcolorpalet\empty
-     \let\currentcolorprefix\empty
+     \lettonothing\currentcolorpalet
+     \lettonothing\currentcolorprefix
     %\t_colo_prefix\emptytoks
    \fi
    \the\everysetuppalet
@@ -1101,8 +1101,8 @@
 %D \stopregistercolor
 %D \stoptyping
 
-\mutable\let\maintextcolor   \empty
-\mutable\def\defaulttextcolor{black}
+\mutable\lettonothing\maintextcolor
+\mutable\def         \defaulttextcolor{black}
 
 \permanent\protected\def\inheritmaintextcolor
   {\ifempty\maintextcolor\else\colo_helpers_activate\maintextcolor\fi}
@@ -1130,7 +1130,7 @@
 
 \permanent\protected\lettonothing\stoptextcolor
 
-\let\p_colo_textcolor\empty
+\lettonothing\p_colo_textcolor
 
 \def\colo_helpers_initialize_maintextcolor
   {\edef\p_colo_textcolor{\directcolorsparameter\c!textcolor}%
diff --git a/tex/context/base/mkxl/cont-log.mkxl b/tex/context/base/mkxl/cont-log.mkxl
index 56cf4053f..710848b67 100644
--- a/tex/context/base/mkxl/cont-log.mkxl
+++ b/tex/context/base/mkxl/cont-log.mkxl
@@ -316,7 +316,6 @@
     \enforced\instance\def\LuaTeX    {LuaTeX}%
     \enforced\instance\def\LuajitTeX {LuajitTeX}%
     \enforced\instance\def\LuaMetaTeX{LuaMetaTeX}%
-   %\let\wordboundary\empty % primitive so we need to promote it to frozen (orjust preroll)
 \to \everysimplifycommands
 
 \protect \endinput
diff --git a/tex/context/base/mkxl/cont-new.mkxl b/tex/context/base/mkxl/cont-new.mkxl
index 12a02f132..b777a015c 100644
--- a/tex/context/base/mkxl/cont-new.mkxl
+++ b/tex/context/base/mkxl/cont-new.mkxl
@@ -13,7 +13,7 @@
 
 % \normalend % uncomment this to get the real base runtime
 
-\newcontextversion{2022.12.09 16:31}
+\newcontextversion{2022.12.15 17:49}
 
 %D This file is loaded at runtime, thereby providing an excellent place for hacks,
 %D patches, extensions and new features. There can be local overloads in cont-loc
diff --git a/tex/context/base/mkxl/context.mkxl b/tex/context/base/mkxl/context.mkxl
index 6ff802992..882be6cc3 100644
--- a/tex/context/base/mkxl/context.mkxl
+++ b/tex/context/base/mkxl/context.mkxl
@@ -29,7 +29,7 @@
 %D {YYYY.MM.DD HH:MM} format.
 
 \immutable\edef\contextformat {\jobname}
-\immutable\edef\contextversion{2022.12.09 16:31}
+\immutable\edef\contextversion{2022.12.15 17:49}
 
 %overloadmode 1 % check frozen / warning
 %overloadmode 2 % check frozen / error
@@ -495,7 +495,7 @@
 \loadmkxlfile{math-lop}
 \loadmklxfile{math-acc}
 \loadmklxfile{math-rad}
-\loadmklxfile{math-del}
+\loadmklxfile{math-dld}
 \loadmkxlfile{math-inl}
 \loadmkxlfile{math-dis}
 %loadmkxlfile{math-lan}
diff --git a/tex/context/base/mkxl/core-con.mkxl b/tex/context/base/mkxl/core-con.mkxl
index 9e2b05778..5a2d50493 100644
--- a/tex/context/base/mkxl/core-con.mkxl
+++ b/tex/context/base/mkxl/core-con.mkxl
@@ -19,8 +19,8 @@
 
 \unprotect
 
-\ifdefined\currentlanguage \else \let\currentlanguage\empty              \fi
-\ifdefined\labeltext       \else \let\labeltext      \firstofoneargument \fi
+\ifdefined\currentlanguage \else \lettonothing\currentlanguage     \fi
+\ifdefined\labeltext       \else \let\labeltext\firstofoneargument \fi
 
 %D This module deals with all kind of conversions from numbers and dates. I
 %D considered splitting this module in a support one and a core one, but to keep
@@ -973,9 +973,9 @@
 
 %D Taken from x-asciimath (see digits-001.tex for an example):
 
-\mutable\let\spaceddigitsmethod   \empty % alternative methods   : 1 default, 2 and 3 only when > 4
-\mutable\let\spaceddigitssymbol   \empty % extra splitter symbol : {,}
-\mutable\let\spaceddigitsseparator\empty % separator symbol      : {\Uchar{"2008}}
+\mutable\lettonothing\spaceddigitsmethod    % alternative methods   : 1 default, 2 and 3 only when > 4
+\mutable\lettonothing\spaceddigitssymbol    % extra splitter symbol : {,}
+\mutable\lettonothing\spaceddigitsseparator % separator symbol      : {\Uchar{"2008}}
 
 \permanent\protected\def\spaceddigits#1%
   {\clf_spaceddigits
diff --git a/tex/context/base/mkxl/core-env.mkxl b/tex/context/base/mkxl/core-env.mkxl
index 77e634212..0777d2823 100644
--- a/tex/context/base/mkxl/core-env.mkxl
+++ b/tex/context/base/mkxl/core-env.mkxl
@@ -383,7 +383,7 @@
 %D The next one is meant for \c!setups situations, hence the check for a
 %D shortcut.
 
-\let\m_syst_setups_asked\empty
+\lettonothing\m_syst_setups_asked
 
 \permanent\protected\def\doprocesslocalsetups#1% sort of public, fast local variant
   {\edef\m_syst_setups_asked{#1}%
@@ -623,7 +623,7 @@
 \permanent\protected\def\setgvariables{\syst_variables_set[\getrawgparameters]}
 \permanent\protected\def\setxvariables{\syst_variables_set[\getrawxparameters]}
 
-\mutable\let\currentvariableclass\empty
+\mutable\lettonothing\currentvariableclass
 
 \tolerant\def\syst_variables_set[#1]#*[#2]#*[#3]% tricky, test on s-pre-60
   {\doifelse{#2}\currentvariableclass
@@ -643,14 +643,12 @@
 \permanent          \def\getvariable #1#2{\begincsname\??variables#1:#2\endcsname}
 \permanent\protected\def\showvariable#1#2{\showvalue{\begincsname\??variables#1:#2\endcsname}}
 
-\let\currentvariableclass\empty
-
 %D \macros
 %D   {checkvariables}
 %D
 %D I'll probably forget that this on exists.
 
-\let\m_syst_variables_temp\empty
+\lettonothing\m_syst_variables_temp
 
 \permanent\tolerant\def\checkvariables[#1]#*[#2]%
   {\dogetparameters\syst_variables_check_value[#1][#2]}
diff --git a/tex/context/base/mkxl/core-ini.mkxl b/tex/context/base/mkxl/core-ini.mkxl
index 41c73b903..4e4c696a7 100644
--- a/tex/context/base/mkxl/core-ini.mkxl
+++ b/tex/context/base/mkxl/core-ini.mkxl
@@ -220,6 +220,7 @@
 
 \let\setlayoutcomponentattribute  \gobbleoneargument
 \let\resetlayoutcomponentattribute\relax
-\let\layoutcomponentboxattribute  \empty
+
+\lettonothing\layoutcomponentboxattribute
 
 \protect \endinput
diff --git a/tex/context/base/mkxl/core-sys.mkxl b/tex/context/base/mkxl/core-sys.mkxl
index b8bd7905e..a928508bb 100644
--- a/tex/context/base/mkxl/core-sys.mkxl
+++ b/tex/context/base/mkxl/core-sys.mkxl
@@ -90,7 +90,7 @@
 
 \permanent\protected\def\setjobfullname#1% #1 = default if not given
   {\doifelsenothing\jobfilename
-     {\let\jobfullname\empty}
+     {\lettonothing\jobfullname}
      {\doif\jobfilesuffix\c!tex{\edef\jobfullname{\jobfilename.#1}}}}
 
 %D There are a couple of system states avaiable:
diff --git a/tex/context/base/mkxl/core-two.mkxl b/tex/context/base/mkxl/core-two.mkxl
index cadd9d059..38f03c7c4 100644
--- a/tex/context/base/mkxl/core-two.mkxl
+++ b/tex/context/base/mkxl/core-two.mkxl
@@ -82,8 +82,9 @@
 
 \setfalse\twopassdatafound
 
-\mutable\let\twopassdata    \empty
-\mutable\let\twopassdatalist\empty
+\mutable\lettonothing\twopassdata
+\mutable\lettonothing\twopassdatalist
+
 \mutable\let\noftwopassitems\!!zeropoint
 
 \def\syst_twopass_check % can be delegated to lua once obsolete is gone
diff --git a/tex/context/base/mkxl/file-ini.mklx b/tex/context/base/mkxl/file-ini.mklx
index 35a49c72d..8febbdea1 100644
--- a/tex/context/base/mkxl/file-ini.mklx
+++ b/tex/context/base/mkxl/file-ini.mklx
@@ -182,11 +182,12 @@
 \newconstant\splitoffkind
 
 \mutable\def\splitoffroot{.}
-\mutable\let\splitofffull\empty
-\mutable\let\splitoffpath\empty
-\mutable\let\splitoffbase\empty
-\mutable\let\splitoffname\empty
-\mutable\let\splitofftype\empty
+
+\mutable\lettonothing\splitofffull
+\mutable\lettonothing\splitoffpath
+\mutable\lettonothing\splitoffbase
+\mutable\lettonothing\splitoffname
+\mutable\lettonothing\splitofftype
 
 \permanent\protected\def\splitfilename{\clf_splitfilename}
 
diff --git a/tex/context/base/mkxl/file-job.mklx b/tex/context/base/mkxl/file-job.mklx
index 58c6aa3d5..8f6c0aa56 100644
--- a/tex/context/base/mkxl/file-job.mklx
+++ b/tex/context/base/mkxl/file-job.mklx
@@ -46,7 +46,7 @@
 
 % helper (not really needed nowadays)
 
-\mutable\let\locatedfilepath\empty
+\mutable\lettonothing\locatedfilepath
 
 \permanent\protected\def\locatefilepath#name%
   {\edef\locatedfilepath{\clf_locatefilepath{#name}}} % todo: set at the lua end, catcodes and such
@@ -289,7 +289,7 @@
    \ifparameters
    \or
      \ifhastok={#namespace}%
-       \let\currentdocument\empty
+       \lettonothing\currentdocument
        \setupcurrentdocument[#namespace]%
      \else
        \edef\currentdocument{#namespace}%
@@ -324,7 +324,7 @@
    \ifparameters
    \or
      \ifhastok={#namespace}%
-       \let\currentdocument\empty
+       \lettonothing\currentdocument
        \setupcurrentdocument[#namespace]%
      \fi
    \or
diff --git a/tex/context/base/mkxl/file-mod.mklx b/tex/context/base/mkxl/file-mod.mklx
index 56e12f72a..c0059bf94 100644
--- a/tex/context/base/mkxl/file-mod.mklx
+++ b/tex/context/base/mkxl/file-mod.mklx
@@ -40,9 +40,10 @@
 
 \installcorenamespace{module}
 
-\mutable\let\currentmodule          \s!unknown
-\mutable\let\currentmodulecategory  \empty
-\mutable\let\currentmoduleparameters\empty
+\mutable\let\currentmodule\s!unknown
+
+\mutable\lettonothing\currentmodulecategory
+\mutable\lettonothing\currentmoduleparameters
 
 \installmacrostack\currentmodule
 \installmacrostack\currentmodulecategory
@@ -53,21 +54,20 @@
    \push_macro_currentmodulecategory
    \push_macro_currentmoduleparameters
    \ifparameters
-     \let\currentmodule\empty
+     \lettonothing\currentmodule
    \or
-     \let \currentmodulecategory  \empty
-     \edef\currentmodule          {#category}%
-     \let \currentmoduleparameters\empty
+     \lettonothing\currentmodulecategory
+     \edef\currentmodule{#category}%
+     \lettonothing\currentmoduleparameters
    \or
      \ifhastok={#name}%
-       \let\currentmodulecategory   \empty
-       \edef\currentmodule          {#category}%
+       \lettonothing\currentmodulecategory
+       \edef\currentmodule{#category}%
        \edef\currentmoduleparameters{#name}%
      \else
-       \edef\currentmodulecategory  {#category}%
-       \edef\currentmodulecategory  {#category}%
-       \edef\currentmodule          {#name}%
-       \let \currentmoduleparameters\empty
+       \edef\currentmodulecategory{#category}%
+       \edef\currentmodule{#name}%
+       \lettonothing\currentmoduleparameters
      \fi
    \or
      \edef\currentmodulecategory  {#category}%
@@ -139,7 +139,7 @@
      \getparameters[\??module#name:][#parameters]% internal (defaults)
      \normalexpanded{\getparameters[\??module#name:][\the\scratchtoks]}% loadtime (user)
    \fi
-   \let\currentmoduleparameters\empty
+   \lettonothing\currentmoduleparameters
    \the\everysetupmodule}
 
 \permanent\def\moduleparameter#name#parameter% should have been \namedmoduleparameter
diff --git a/tex/context/base/mkxl/file-res.mklx b/tex/context/base/mkxl/file-res.mklx
index a123b5e22..a62408921 100644
--- a/tex/context/base/mkxl/file-res.mklx
+++ b/tex/context/base/mkxl/file-res.mklx
@@ -62,7 +62,7 @@
 %D to redefine the original \type {\input} when needed, for instance when loading
 %D third party libraries.
 
-\mutable\let\readfilename\empty
+\mutable\lettonothing\readfilename
 
 \def\syst_files_read_file#protocol#path#name% #true #false
   {\edef\readfilename{\clf_getreadfilename{#protocol}{#path}{#name}}%
diff --git a/tex/context/base/mkxl/font-col.mklx b/tex/context/base/mkxl/font-col.mklx
index bd099bbe9..03515201f 100644
--- a/tex/context/base/mkxl/font-col.mklx
+++ b/tex/context/base/mkxl/font-col.mklx
@@ -34,7 +34,7 @@
 \permanent\tolerant\protected\def\definefontfallback[#name]#spacer[#font]#spacer[#ranges]#spacer[#settings]%
   {\let\mathsizesuffix\relax
    \clf_fontcollectiondefine{#name}{#font}{#ranges}{#settings}%
-   \let\mathsizesuffix\empty}
+   \lettonothing\mathsizesuffix}
 
 \permanent\tolerant\protected\def\resetfontfallback[#name]#spacer[#font]%
   {\clf_fontcollectionreset{#name}{#font}}
@@ -54,7 +54,7 @@
      \font_fallbacks_prepare#fallbacks%
    \endgroup}
 
-\let\m_font_fallbacks\empty % set in the font-ini
+\lettonothing\m_font_fallbacks % set in the font-ini
 
 \appendtoks
     \ifconditional\c_font_fallbacks_in_progress\else
@@ -68,7 +68,7 @@
    \fi
 \to\everydefinefont
 
-\let\m_font_fallbacks_spec\empty
+\lettonothing\m_font_fallbacks_spec
 
 \def\font_fallbacks_start_cloning
   {\begingroup
diff --git a/tex/context/base/mkxl/font-emp.mklx b/tex/context/base/mkxl/font-emp.mklx
index e99f74afd..dfb97426c 100644
--- a/tex/context/base/mkxl/font-emp.mklx
+++ b/tex/context/base/mkxl/font-emp.mklx
@@ -38,7 +38,7 @@
 %D
 %D or even better:
 
-\let\m_font_emphasized_typeface\empty
+\lettonothing\m_font_emphasized_typeface
 
 \def\font_emphasis_checked_typeface#slanted#italic%
   {\edef\m_font_emphasized_typeface{\font_bodyfontvariable\s!em}%
diff --git a/tex/context/base/mkxl/font-fea.mklx b/tex/context/base/mkxl/font-fea.mklx
index 9f4d2119e..3e6a4b2eb 100644
--- a/tex/context/base/mkxl/font-fea.mklx
+++ b/tex/context/base/mkxl/font-fea.mklx
@@ -136,12 +136,10 @@
 
 % beware: these are global features on top of existing font features
 
-\mutable\let\currentfeature\s!current
-
-\let\m_font_feature_list \s!current
-\let\m_font_feature_asked\empty
-
-\newconstant\c_font_feature_state
+\mutable\let \currentfeature      \s!current
+\let         \m_font_feature_list \s!current
+\lettonothing\m_font_feature_asked
+\newconstant \c_font_feature_state
 
 \newevery\everyfontfeatureswitch
 
@@ -193,7 +191,7 @@
    \the\everyfontfeatureswitch}
 
 \protected\def\font_feature_replace
-  {\ifnum\c_font_feature_state=\zerocount
+  {\ifzero\c_font_feature_state
      \ifx\m_font_feature_asked\currentfeature\else
        \font_feature_replace_indeed
      \fi
@@ -214,9 +212,9 @@
    \fi}
 
 \protected\def\font_feature_reset_indeed
-  {\let\m_font_feature_asked\empty
-   \let\currentfeature      \s!current
-   \let\m_font_feature_list \s!current
+  {\lettonothing\m_font_feature_asked
+   \let\currentfeature\s!current
+   \let\m_font_feature_list\s!current
    \clf_resetfeature}
 
 \permanent\protected\def\revivefeature
diff --git a/tex/context/base/mkxl/font-fil.mklx b/tex/context/base/mkxl/font-fil.mklx
index b71f8df69..79535ea11 100644
--- a/tex/context/base/mkxl/font-fil.mklx
+++ b/tex/context/base/mkxl/font-fil.mklx
@@ -44,7 +44,7 @@
 \permanent\protected\tolerant\protected\def\startfontclass[#class]%
   {\push_macro_fontclass
    \doifelse{#class}\v!each
-     {\let\fontclass\empty}
+     {\lettonothing\fontclass}
      {\doifsomething{#class}{\def\fontclass{#class}}}}
 
 \permanent\protected\def\stopfontclass
@@ -65,8 +65,8 @@
 
 \installcorenamespace {fontfile} % file synonyms
 
-\let\m_font_name\empty
-\let\m_font_file\empty
+\lettonothing\m_font_name
+\lettonothing\m_font_file
 
 \mutable\def\defaultfontfile{\truefontname{Normal}} % was cmtt10, but that one is gone
 
@@ -141,7 +141,7 @@
 
 % \def\fntsetdefname {\glet\somefontname\defaultfontfile}
 % \def\fntsetsomename{\gdef\somefontname} % takes argument
-% \def\fntsetnopsize {\let\somefontsize\empty}
+% \def\fntsetnopsize {\lettonothing\somefontsize}
 % \def\fntsetsomesize{\def\somefontsize}  % takes argument
 
 % happens later, else mkvi parsing gets into troubles
@@ -272,8 +272,8 @@
 %D model and at that time we still defaulted to no model at all. Nowadays we default
 %D to the \type {modern} fontclass.
 
-\let\fontclass       \empty
-\let\defaultfontclass\empty
+\lettonothing\fontclass
+\lettonothing\defaultfontclass
 
 \permanent\def\fontclassname#class#name% tricky ... no lastnamedcs here due to nesting
   {\ifcsname\??fontfile#class#name\endcsname
@@ -307,48 +307,48 @@
    \ifcsname\??fontfile          #name\s!features\endcsname \edef\m_font_features{\lastnamedcs}\orelse          % symbolic_name
    \ifcsname\??fontfile\fontclass#name\endcsname \expandafter\font_helpers_set_features_yes\lastnamedcs \orelse % class + parent_name
    \ifcsname\??fontfile          #name\endcsname \expandafter\font_helpers_set_features_yes\lastnamedcs \else   % parent_name
-   \let\m_font_features\empty\fi}
+   \lettonothing\m_font_features\fi}
 
 \def\font_helpers_set_fallbacks_yes#name%
   {\ifcsname\??fontfile\fontclass#name\s!fallbacks\endcsname \edef\m_font_fallbacks{\lastnamedcs}\orelse
    \ifcsname\??fontfile          #name\s!fallbacks\endcsname \edef\m_font_fallbacks{\lastnamedcs}\orelse
    \ifcsname\??fontfile\fontclass#name\endcsname \expandafter\font_helpers_set_fallbacks_yes\lastnamedcs \orelse
    \ifcsname\??fontfile          #name\endcsname \expandafter\font_helpers_set_fallbacks_yes\lastnamedcs \else
-   \let\m_font_fallbacks\empty\fi}
+   \lettonothing\m_font_fallbacks\fi}
 
 \def\font_helpers_set_goodies_yes#name%
   {\ifcsname\??fontfile\fontclass#name\s!goodies  \endcsname \edef\m_font_goodies{\lastnamedcs}\orelse
    \ifcsname\??fontfile          #name\s!goodies  \endcsname \edef\m_font_goodies{\lastnamedcs}\orelse
    \ifcsname\??fontfile\fontclass#name\endcsname \expandafter\font_helpers_set_goodies_yes\lastnamedcs \orelse
    \ifcsname\??fontfile          #name\endcsname \expandafter\font_helpers_set_goodies_yes\lastnamedcs \else
-   \let\m_font_goodies\empty\fi}
+   \lettonothing\m_font_goodies\fi}
 
 \def\font_helpers_set_designsize_yes#name%
   {\ifcsname\??fontfile\fontclass#name\s!designsize\endcsname \edef\m_font_designsize{\lastnamedcs}\orelse
    \ifcsname\??fontfile          #name\s!designsize\endcsname \edef\m_font_designsize{\lastnamedcs}\orelse
    \ifcsname\??fontfile\fontclass#name\endcsname \expandafter\font_helpers_set_designsize_yes\lastnamedcs \orelse
    \ifcsname\??fontfile          #name\endcsname \expandafter\font_helpers_set_designsize_yes\lastnamedcs \else
-   \let\m_font_designsize\empty\fi}
+   \lettonothing\m_font_designsize\fi}
 
 \def\font_helpers_set_features_nop#name%
   {\ifcsname\??fontfile#name\s!features\endcsname \edef\m_font_features{\lastnamedcs}\orelse
    \ifcsname\??fontfile#name\endcsname \expandafter\font_helpers_set_features_nop\lastnamedcs \else
-   \let\m_font_features\empty\fi}
+   \lettonothing\m_font_features\fi}
 
 \def\font_helpers_set_fallbacks_nop#name%
   {\ifcsname\??fontfile#name\s!fallbacks\endcsname \edef\m_font_fallbacks{\lastnamedcs}\orelse
    \ifcsname\??fontfile#name\endcsname \expandafter\font_helpers_set_fallbacks_nop\lastnamedcs \else
-   \let\m_font_fallbacks\empty\fi}
+   \lettonothing\m_font_fallbacks\fi}
 
 \def\font_helpers_set_goodies_nop#name%
   {\ifcsname\??fontfile#name\s!goodies\endcsname \edef\m_font_goodies{\lastnamedcs}\orelse
    \ifcsname\??fontfile#name\endcsname \expandafter\font_helpers_set_goodies_nop\lastnamedcs \else
-   \let\m_font_goodies\empty\fi}
+   \lettonothing\m_font_goodies\fi}
 
 \def\font_helpers_set_designsize_nop#name%
   {\ifcsname\??fontfile#name\s!designsize\endcsname \edef\m_font_designsize{\lastnamedcs}\orelse
    \ifcsname\??fontfile#name\endcsname \expandafter\font_helpers_set_designsize_nop\lastnamedcs \else
-   \let\m_font_designsize\empty\fi}
+   \lettonothing\m_font_designsize\fi}
 
 \def\font_helpers_update_font_parameters_yes
   {\font_helpers_set_features_yes  \somefontname
diff --git a/tex/context/base/mkxl/font-ini.mklx b/tex/context/base/mkxl/font-ini.mklx
index 5e521e263..f1691c8eb 100644
--- a/tex/context/base/mkxl/font-ini.mklx
+++ b/tex/context/base/mkxl/font-ini.mklx
@@ -333,7 +333,7 @@
    \the\everybodyfont
    \settrue\c_font_synchronize}
 
-\mutable\let\savedfont\empty
+\mutable\lettonothing\savedfont
 
 \installmacrostack\savedfont
 
@@ -712,8 +712,9 @@
 \mutable\let\somefontspec \s!unknown
 \mutable\let\somefontfile \s!unknown
 \mutable\let\somefontsize \zerocount
-\mutable\let\somefontsizex\empty
-\mutable\let\somefontsizey\empty
+
+\mutable\lettonothing\somefontsizex
+\mutable\lettonothing\somefontsizey
 
 % \newcount\scaledfontmode % font-lib.mklx
 % \newcount\scaledfontsize % font-lib.mklx
@@ -747,7 +748,8 @@
 % \newcount\c_font_scaled_font_mode_saved % font-lib.mklx
 % \newcount\c_font_scaled_points          % font-lib.mklx
 
-\mutable\let\somefontspec         \empty
+\mutable\lettonothing\somefontspec
+
 \mutable\let\lastrawfontcall      \relax
 \mutable\let\lastglobalrawfontcall\relax
 
@@ -763,9 +765,9 @@
 \protected\def\font_helpers_low_level_define_normal#specification#csname%
   {% we can now set more at the lua end
    \glet\somefontname\defaultfontfile
-   \let\somefontsize\empty
-   \let\somefontsizex\empty
-   \let\somefontsizey\empty
+   \lettonothing\somefontsize
+   \lettonothing\somefontsizex
+   \lettonothing\somefontsizey
    \clf_definefont_one{\detokenize\expandafter{\normalexpanded{#specification}}}% the escapestring catches at \somedimen
    % sets \scaledfontmode and \somefontname and \somefontsize
    \ifcase\fontface\relax
@@ -849,7 +851,7 @@
    \relax
    \ifcase\scaledfontsize
     %\scaledfontsize\plusone
-     \let\somefontspec\empty
+     \lettonothing\somefontspec
      \let\lastrawfontcall\relax
      \mutable\letcsname#csname\endcsname\relax
    \else
@@ -862,9 +864,9 @@
 \protected\def\font_helpers_low_level_define_compact#specification#csname%
   {% we can now set more at the lua end
    \glet\somefontname\defaultfontfile
-   \let\somefontsize\empty
-   \let\somefontsizex\empty
-   \let\somefontsizey\empty
+   \lettonothing\somefontsize
+   \lettonothing\somefontsizex
+   \lettonothing\somefontsizey
    \clf_definefont_one{\detokenize\expandafter{\normalexpanded{#specification}}}% the escapestring catches at \somedimen
    % sets \scaledfontmode and \somefontname and \somefontsize
    \ifcase\fontface\relax
@@ -961,7 +963,7 @@
    \relax
    \ifcase\scaledfontsize
     %\scaledfontsize\plusone
-     \let\somefontspec\empty
+     \lettonothing\somefontspec
      \let\lastrawfontcall\relax
      \mutable\letcsname#csname\endcsname\relax
    \else
@@ -980,7 +982,7 @@
      % experiment
      \expandafter\let\expandafter\lastrawfontcall\csname#csname\endcsname
      \ifrelax\lastrawfontcall
-       \let\somefontspec\empty
+       \lettonothing\somefontspec
      \else
      %
      % \ifempty\fontclass\else\global\fi
@@ -1162,7 +1164,7 @@
 
 \newconditional\c_font_auto_size \settrue\c_font_auto_size
 
-\mutable\let\lastfontidentifier\empty
+\mutable\lettonothing\lastfontidentifier
 
 \def\v_font_identifier_basic{\??fontinstancebasic           \lastfontidentifier-\fontsize-\fontface}
 \def\v_font_identifier_class{\??fontinstanceclass\fontclass-\lastfontidentifier-\fontsize-\fontface}
@@ -1455,13 +1457,13 @@
 
 \def\font_basics_define_body_font_environment_empty[#body][#settings][#dummy]%
   {\push_macro_fontclass
-   \let\fontclass\empty
+   \lettonothing\fontclass
    \font_basics_define_body_font_environment_class[][#body][#settings]%
    \pop_macro_fontclass}
 
 \def\font_basics_define_body_font_environment_unset[#body][#dummya][#dummyb]%
   {\push_macro_fontclass
-   \let\fontclass\empty
+   \lettonothing\fontclass
    \font_basics_define_body_font_environment_class[][#body][]%
    \pop_macro_fontclass}
 
@@ -1604,7 +1606,7 @@
 \protected\def\font_basics_define_body_font_class_given[#1][#2][#3]#4%
   {\push_macro_fontclass
    \doifelse{#4}\s!default
-     {\let\fontclass\empty}
+     {\lettonothing\fontclass}
      {\def\fontclass{#4}}%
    \definebodyfont[#1][#2][#3]%
    \pop_macro_fontclass}
@@ -1914,8 +1916,8 @@
      \edef\m_font_step{\font_bodyfontvariable\m_font_keyword}%
      \normalexpanded{\font_helpers_set_font_set_font_option_body{#method}{\m_font_step}{#message}}%
    \orelse\ifx\m_font_keyword\v!reset
-     \let\fontstyle\empty % new 31/7/2006
-     \let\fontsize \empty
+     \lettonothing\fontstyle % new 31/7/2006
+     \lettonothing\fontsize
    \orelse\ifcsname\??fontstyle\m_font_keyword\endcsname
      \let\fontstyle\m_font_keyword
    \else
@@ -1965,11 +1967,6 @@
 
 \fi
 
-% \let\defaultfontstyle      \s!rm
-% \let\defaultfontalternative\s!tf
-% \let\defaultfontsize       \empty
-% \let\defaultfontface       \!!zerocount
-
 %D So far for synchronisation. (We can inline the following macros.)
 
 \permanent\protected\def\setcurrentfont#body#style#alternative#size% not used
@@ -2192,8 +2189,8 @@
   {\font_helpers_check_nested_x_fontsize
    \font_helpers_set_current_font_xxx_alternative{#alternative}{5}\scriptscriptstyle
    \currentxfontsize\plustwo
-   \enforced\let\tx\empty
-   \enforced\let\txx\empty}
+   \enforced\lettonothing\tx
+   \enforced\lettonothing\txx}
 
 %D This alternative is not really needed, but for old time's sake we keep it there.
 %D We can speed it up when needed.
@@ -2369,8 +2366,8 @@
    \else
      \font_scale_defined_xx
    \fi
-   \enforced\let\tx \empty
-   \enforced\let\txx\empty}
+   \enforced\lettonothing\tx
+   \enforced\lettonothing\txx}
 
 \permanent\protected\def\sx
   {\currentxfontsize\plusone
@@ -2397,10 +2394,10 @@
        \font_scale_inherit_normal_xx
      \fi
    \fi
-   \enforced\let\tx \empty
-   \enforced\let\txx\empty
-   \enforced\let\sx \empty
-   \enforced\let\sxx\empty}
+   \enforced\lettonothing\tx
+   \enforced\lettonothing\txx
+   \enforced\lettonothing\sx
+   \enforced\lettonothing\sxx}
 
 \permanent\protected\def\useinheritxsizes{\settrue \c_font_inherit_scale} % not yet public, playground for WS and me
 \permanent\protected\def\usedefinedxsizes{\setfalse\c_font_inherit_scale} % not yet public, playground for WS and me
diff --git a/tex/context/base/mkxl/font-mat.mklx b/tex/context/base/mkxl/font-mat.mklx
index 39ed13069..e7a7574a3 100644
--- a/tex/context/base/mkxl/font-mat.mklx
+++ b/tex/context/base/mkxl/font-mat.mklx
@@ -121,7 +121,7 @@
                                                                                                   \settrue \c_font_auto_size
    \fi}
 
-\mutable\let\mathsizesuffix\empty
+\mutable\lettonothing\mathsizesuffix
 
 \mutable\let\fontfamily\relax % for now public but it is a helper
 
@@ -134,16 +134,20 @@
    % the order is important as we depend on known id's when completing fonts
    % enabling is needed when we have fallbacks which spoils the families; per
    % mid 2022 this is no longer true as we do fallbacks differently
-   \let\mathsizesuffix\mathscriptscriptsuffix\let\fontface\!!plusthree
+   \let\mathsizesuffix\mathscriptscriptsuffix
+   \let\fontface\!!plusthree
    \font_helpers_set_math_family_a\scriptscriptfont#mrtag\font % defines
    \font_helpers_set_math_family_a\scriptscriptfont#mrtag\font % enables / still needed ?
-   \let\mathsizesuffix\mathscriptsuffix      \let\fontface\!!plustwo
+   \let\mathsizesuffix\mathscriptsuffix
+   \let\fontface\!!plustwo
    \font_helpers_set_math_family_a\scriptfont      #mrtag\font % defines
    \font_helpers_set_math_family_a\scriptfont      #mrtag\font % enables / still needed ?
-   \let\mathsizesuffix\mathtextsuffix        \let\fontface\!!plusone
+   \let\mathsizesuffix\mathtextsuffix
+   \let\fontface\!!plusone
    \font_helpers_set_math_family_a\textfont        #mrtag\font % defines
    \font_helpers_set_math_family_a\textfont        #mrtag\font % enables / still needed ?
-   \let\mathsizesuffix\empty                 \let\fontface\!!zerocount
+   \lettonothing\mathsizesuffix
+   \let\fontface\!!zerocount
    \let\fontbody\savedfontbody
    \setfalse\c_font_auto_size}
 
@@ -166,12 +170,14 @@
    \font_helpers_set_math_family_set_scales_compact
    % the order is important as we depend on known id's when completing fonts
    % enabling is needed when we have fallbacks which spoils the families
-   \let\mathsizesuffix\mathtextsuffix        \let\fontface\!!plusone
+   \let\mathsizesuffix\mathtextsuffix
+   \let\fontface\!!plusone
    \font_helpers_set_math_family_a\textfont        #mrtag\font % defines
    \font_helpers_set_math_family_a\textfont        #mrtag\font % enables / still needed ?
                                   \scriptfont      #mrtag\font % reuses
                                   \scriptscriptfont#mrtag\font % reuses
-   \let\mathsizesuffix\empty                 \let\fontface\!!zerocount
+   \lettonothing\mathsizesuffix
+   \let\fontface\!!zerocount
    \let\fontbody\savedfontbody
    \setfalse\c_font_auto_size}
 
@@ -189,16 +195,20 @@
    \let\fontfamily#familytag%
 \c_math_last_family_used\zerocount
    \font_helpers_set_math_family_set_scales_normal
-   \let\mathsizesuffix\mathscriptscriptsuffix\let\fontface\!!plusthree
+   \let\mathsizesuffix\mathscriptscriptsuffix
+   \let\fontface\!!plusthree
    \font_helpers_set_math_family_bold_a\scriptscriptfont#mbfam#mrfam% defines
    \font_helpers_set_math_family_bold_a\scriptscriptfont#mbfam#mrfam% enables / still needed ?
-   \let\mathsizesuffix\mathscriptsuffix      \let\fontface\!!plustwo
+   \let\mathsizesuffix\mathscriptsuffix
+   \let\fontface\!!plustwo
    \font_helpers_set_math_family_bold_a\scriptfont      #mbfam#mrfam% defines
    \font_helpers_set_math_family_bold_a\scriptfont      #mbfam#mrfam% enables / still needed ?
-   \let\mathsizesuffix\mathtextsuffix        \let\fontface\!!plusone
+   \let\mathsizesuffix\mathtextsuffix
+   \let\fontface\!!plusone
    \font_helpers_set_math_family_bold_a\textfont        #mbfam#mrfam% defines
    \font_helpers_set_math_family_bold_a\textfont        #mbfam#mrfam% enables / still needed ?
-   \let\mathsizesuffix\empty                 \let\fontface\!!zerocount
+   \lettonothing\mathsizesuffix
+   \let\fontface\!!zerocount
    \let\fontbody\savedfontbody
    \let\defaultfontclass\savedfontclass
    \setfalse\c_font_auto_size}
@@ -209,12 +219,14 @@
    \let\savedfontbody\fontbody
    \let\fontfamily#familytag%
 \c_math_last_family_used\zerocount
-   \let\mathsizesuffix\mathtextsuffix        \let\fontface\!!plusone
+   \let\mathsizesuffix\mathtextsuffix
+   \let\fontface\!!plusone
    \font_helpers_set_math_family_bold_a\textfont        #mbfam#mrfam% defines
    \font_helpers_set_math_family_bold_a\textfont        #mbfam#mrfam% enables / still needed ?
                                        \scriptfont      #mbfam\textfont#mbfam% reuses
                                        \scriptscriptfont#mbfam\textfont#mbfam% reuses
-   \let\mathsizesuffix\empty                 \let\fontface\!!zerocount
+   \lettonothing\mathsizesuffix
+   \let\fontface\!!zerocount
    \let\fontbody\savedfontbody
    \let\defaultfontclass\savedfontclass
    \setfalse\c_font_auto_size}
@@ -325,15 +337,15 @@
 %D 0 while in rl mode 0 is a copy of 1. There is no real overhead involved in this.
 %D This also permits different font definitions for normal and mixed.
 
-\let\m_font_class_direction\empty
-\let\m_font_class_features \empty
-\let\m_font_class_fallbacks\empty
-\let\m_font_class_goodies  \empty
+\lettonothing\m_font_class_direction
+\lettonothing\m_font_class_features
+\lettonothing\m_font_class_fallbacks
+\lettonothing\m_font_class_goodies
 
-\let\m_font_direction\empty
-\let\m_font_features \empty
-\let\m_font_fallbacks\empty
-\let\m_font_goodies  \empty
+\lettonothing\m_font_direction
+\lettonothing\m_font_features
+\lettonothing\m_font_fallbacks
+\lettonothing\m_font_goodies
 
 \appendtoks
     \font_helpers_set_math_family\c_font_fam_mr\s!mr
@@ -474,7 +486,7 @@
 \permanent\protected\def\autobigmath{\synchronizebigmathflag\plusone\synchronizebigmath}
 \permanent\protected\def\bigmath    {\synchronizebigmathflag\plustwo\synchronizebigmath}
 
-\mutable\let\bigmathfontsize\empty
+\mutable\lettonothing\bigmathfontsize
 
 \permanent\protected\def\synchronizebigmath
   {\ifconditional\c_font_compact
diff --git a/tex/context/base/mkxl/font-sel.mklx b/tex/context/base/mkxl/font-sel.mklx
index a25b7fab7..9e5c53894 100644
--- a/tex/context/base/mkxl/font-sel.mklx
+++ b/tex/context/base/mkxl/font-sel.mklx
@@ -269,7 +269,7 @@
      \edef\currentselectfont{\expandnamespacevalue\??fontshortstyle{#style}\s!rm}%
      \setupcurrentselectfont[#settings]%
    \else
-     \let\currentselectfont\empty
+     \lettonothing\currentselectfont
      \setupcurrentselectfont[#style]%
    \fi}
 
diff --git a/tex/context/base/mkxl/font-set.mklx b/tex/context/base/mkxl/font-set.mklx
index 631c4af05..421217c8b 100644
--- a/tex/context/base/mkxl/font-set.mklx
+++ b/tex/context/base/mkxl/font-set.mklx
@@ -34,7 +34,7 @@
 
 % \enablemode[lmmath]
 
-\let\m_font_fallback_name\empty
+\lettonothing\m_font_fallback_name
 
 % keep as reference:
 %
diff --git a/tex/context/base/mkxl/font-sol.mklx b/tex/context/base/mkxl/font-sol.mklx
index 8f3d3d712..064f39b9d 100644
--- a/tex/context/base/mkxl/font-sol.mklx
+++ b/tex/context/base/mkxl/font-sol.mklx
@@ -107,11 +107,11 @@
      }%
    \relax}
 
-\let\currentfontsolution\empty
+\lettonothing\currentfontsolution
 
 \permanent\protected\def\resetfontsolution % resets all
   {\clf_resetfontsolution
-   \let\currentfontsolution\empty}
+   \lettonothing\currentfontsolution}
 
 \permanent\protected\def\startfontsolution % [#1]
   {\pushmacro\currentfontsolution
diff --git a/tex/context/base/mkxl/font-sty.mklx b/tex/context/base/mkxl/font-sty.mklx
index 5391f39b6..49fa52d38 100644
--- a/tex/context/base/mkxl/font-sty.mklx
+++ b/tex/context/base/mkxl/font-sty.mklx
@@ -142,8 +142,8 @@
 %D These commands are not grouped! Grouping is most probably done by the calling
 %D macro's and would lead to unnecessary overhead.
 
-\let\m_current_convert_font   \empty
-\let\m_current_convert_font_dt\empty
+\lettonothing\m_current_convert_font
+\lettonothing\m_current_convert_font_dt
 
 \permanent\protected\def\doconvertfont#specification% takes second argument / this command is obsolete
   {\edef\m_current_convert_font{#specification}%
@@ -180,7 +180,7 @@
 
 \setfalse\fontattributeisset
 
-\mutable\let\currentdetokenizedstyleparameter\empty
+\mutable\lettonothing\currentdetokenizedstyleparameter
 
 \permanent\protected\def\dousestyleparameter#value%
   {\edef\currentstyleparameter{#value}%
@@ -259,8 +259,8 @@
 
 \protected\def\font_styles_use_generic#specification%
   {\let\currentstyle\s!unknown % reasonable generic tag
-   \letstyleparameter\c!style\empty
-   \letstyleparameter\c!color\empty
+   \resetstyleparameter\c!style
+   \resetstyleparameter\c!color
    \setupcurrentstyle[#specification]%
    \usestylestyleandcolor\c!style\c!color}
 
diff --git a/tex/context/base/mkxl/font-sym.mklx b/tex/context/base/mkxl/font-sym.mklx
index e1de316ef..83b3447ea 100644
--- a/tex/context/base/mkxl/font-sym.mklx
+++ b/tex/context/base/mkxl/font-sym.mklx
@@ -129,9 +129,9 @@
 
 \installcorenamespace{symbolfont}
 
-\mutable\let\skedsymbolfont   \empty % for diagnostics
-\mutable\let\currentsymbolfont\empty
-\mutable\let\askedsymbolfont  \empty
+\mutable\lettonothing\skedsymbolfont    % for diagnostics
+\mutable\lettonothing\currentsymbolfont
+\mutable\lettonothing\askedsymbolfont
 
 \permanent\protected\def\setscaledstyledsymbolicfont#1#2#3% quite a slowdown, glyphfontfile
   {\edef\askedsymbolfont{\truefontname{\glyphfontfile{#3}} at \the\dimexpr#2\dimexpr\currentfontbodyscale\dimexpr#1}%
diff --git a/tex/context/base/mkxl/font-var.mklx b/tex/context/base/mkxl/font-var.mklx
index 421521f50..aeec18054 100644
--- a/tex/context/base/mkxl/font-var.mklx
+++ b/tex/context/base/mkxl/font-var.mklx
@@ -38,17 +38,19 @@
 \immutable\def\defaultfontbody      {\normalizedbodyfontsize}
 \immutable\let\defaultfontstyle      \s!rm
 \immutable\let\defaultfontalternative\s!tf
-\immutable\let\defaultfontsize       \empty
 \immutable\let\defaultfontface       \!!zerocount
 
-\mutable\let\globalfontclass\empty
-\mutable\let\fontclass      \empty
+\immutable\lettonothing\defaultfontsize
+
 \mutable\let\fontbody       \defaultfontbody
 \mutable\let\fontstyle      \defaultfontstyle
 \mutable\let\fontalternative\defaultfontalternative
 \mutable\let\fontsize       \defaultfontsize
 \mutable\let\fontface       \!!zerocount
 
+\mutable\lettonothing\globalfontclass
+\mutable\lettonothing\fontclass
+
 \installmacrostack\fontstyle
 
 % we can use an indirect mapping for fontclasses (map string onto numbers) and indeed this
diff --git a/tex/context/base/mkxl/grph-epd.mkxl b/tex/context/base/mkxl/grph-epd.mkxl
index c8e5cd1c8..a26ee3235 100644
--- a/tex/context/base/mkxl/grph-epd.mkxl
+++ b/tex/context/base/mkxl/grph-epd.mkxl
@@ -19,7 +19,7 @@
 
 % hm, this one is globally overloaded
 
-\mutable\let\mergedfigurereference\empty
+\mutable\lettonothing\mergedfigurereference
 
 \defineoverlay[system:graphics:epdf][\directsetup{system:graphics:epdf}]
 
diff --git a/tex/context/base/mkxl/grph-fig.mkxl b/tex/context/base/mkxl/grph-fig.mkxl
index dc709c477..0d4462730 100644
--- a/tex/context/base/mkxl/grph-fig.mkxl
+++ b/tex/context/base/mkxl/grph-fig.mkxl
@@ -31,7 +31,7 @@
 
 \newconstant\c_grph_buffers_mode
 
-\mutable\let\lasttypesetbuffer\empty
+\mutable\lettonothing\lasttypesetbuffer
 
 \permanent\protected\def\typesetbuffer    {\bgroup\setconstant\c_grph_buffers_mode\plusone  \grph_buffers_typeset}
 \permanent\protected\def\typesetbufferonly{\bgroup\setconstant\c_grph_buffers_mode\zerocount\grph_buffers_typeset}
diff --git a/tex/context/base/mkxl/grph-inc.mkxl b/tex/context/base/mkxl/grph-inc.mkxl
index 29efe620f..19cce3511 100644
--- a/tex/context/base/mkxl/grph-inc.mkxl
+++ b/tex/context/base/mkxl/grph-inc.mkxl
@@ -806,7 +806,7 @@
       \ifdim\scratchdimen<\d_grph_include_collection_minheight \d_grph_include_collection_minheight\scratchdimen \fi
    \fi}
 
-\mutable\let\currentexternalfigurecollection\empty
+\mutable\lettonothing\currentexternalfigurecollection
 
 \permanent\protected\def\startexternalfigurecollection[#1]%
   {\begingroup
diff --git a/tex/context/base/mkxl/grph-trf.mkxl b/tex/context/base/mkxl/grph-trf.mkxl
index 0f1458873..639eacbbc 100644
--- a/tex/context/base/mkxl/grph-trf.mkxl
+++ b/tex/context/base/mkxl/grph-trf.mkxl
@@ -61,9 +61,9 @@
 
 % scratch:
 
-\let\m_grph_scale_temp  \empty
-\let\m_grph_scale_temp_x\empty
-\let\m_grph_scale_temp_y\empty
+\lettonothing\m_grph_scale_temp
+\lettonothing\m_grph_scale_temp_x
+\lettonothing\m_grph_scale_temp_y
 
 % public:
 
@@ -104,10 +104,10 @@
   {\bgroup
    % this is quite common so we might make this a helper
    \ifarguments
-     \let\currentscale\empty
+     \lettonothing\currentscale
    \or
      \ifhastok={#1}%
-       \let\currentscale\empty
+       \lettonothing\currentscale
        \setupcurrentscale[#1]%
      \else
        \edef\currentscale{#1}%
@@ -795,8 +795,8 @@
    \c!offset=\v!overlay,
    \c!frame=\v!off]
 
-\let\p_rotation_location\empty
-\let\p_rotation_rotation\empty
+\lettonothing\p_rotation_location
+\lettonothing\p_rotation_rotation
 
 \permanent\tolerant\protected\def\rotate[#1]% \bgroup: \rotate kan argument zijn
   {\bgroup
diff --git a/tex/context/base/mkxl/hand-ini.mkxl b/tex/context/base/mkxl/hand-ini.mkxl
index 1d4dabf6b..3a4193f1a 100644
--- a/tex/context/base/mkxl/hand-ini.mkxl
+++ b/tex/context/base/mkxl/hand-ini.mkxl
@@ -73,7 +73,7 @@
 
 % \def\fonthandlingerror{\writestatus\m!fonts{font handling is replaced by features in mkiv}}
 %
-% \let\fonthandling\empty
+% \lettonothing\fonthandling
 %
 % \protected\def\startfonthandling  #1{\fonthandlingerror\fonthandlingerror\gobbleuntil\stopfonthandling} % can't happen
 % \protected\def\definefonthandling   {\dotripleempty\dodefinefonthandling}
diff --git a/tex/context/base/mkxl/lang-hyp.mkxl b/tex/context/base/mkxl/lang-hyp.mkxl
index ae8b84dcb..25699696e 100644
--- a/tex/context/base/mkxl/lang-hyp.mkxl
+++ b/tex/context/base/mkxl/lang-hyp.mkxl
@@ -107,19 +107,19 @@
 %   [\c!method=\s!traditional] % no translations
 
 \permanent\tolerant\protected\def\definehyphenationfeatures[#1]#*[#2]%
-  {\begingroup
-   \letdummyparameter\c!characters     \empty     % maybe \s!characters
-   \letdummyparameter\c!hyphens        \empty     % maybe \s!hyphens
-   \letdummyparameter\c!joiners        \empty     % maybe \s!joiners
-   \letdummyparameter\c!rightwords     \zerocount % maybe \s!rightwords
-   \letdummyparameter\s!lefthyphenmin  \zerocount
-   \letdummyparameter\s!righthyphenmin \zerocount
-   \letdummyparameter\s!hyphenmin      \zerocount
-   \letdummyparameter\s!lefthyphenchar \zerocount
-   \letdummyparameter\s!righthyphenchar\zerocount
-   \letdummyparameter\c!alternative    \empty
-   \letdummyparameter\c!rightedge      \empty
-   \letdummyparameter\c!rightchars     \empty
+  {\begingroup % maybe simple handler
+   \resetdummyparameter\c!characters                % maybe \s!characters
+   \resetdummyparameter\c!hyphens                   % maybe \s!hyphens
+   \resetdummyparameter\c!joiners                   % maybe \s!joiners
+   \letdummyparameter  \c!rightwords     \zerocount % maybe \s!rightwords
+   \letdummyparameter  \s!lefthyphenmin  \zerocount
+   \letdummyparameter  \s!righthyphenmin \zerocount
+   \letdummyparameter  \s!hyphenmin      \zerocount
+   \letdummyparameter  \s!lefthyphenchar \zerocount
+   \letdummyparameter  \s!righthyphenchar\zerocount
+   \resetdummyparameter\c!alternative
+   \resetdummyparameter\c!rightedge
+   \resetdummyparameter\c!rightchars
    \getdummyparameters[#2]%
    \clf_definehyphenationfeatures
       {#1}%
diff --git a/tex/context/base/mkxl/lang-ini.mkxl b/tex/context/base/mkxl/lang-ini.mkxl
index ff9f5cfda..9acc2535b 100644
--- a/tex/context/base/mkxl/lang-ini.mkxl
+++ b/tex/context/base/mkxl/lang-ini.mkxl
@@ -58,9 +58,9 @@
 %D    \startmode[*nl] dutch   \stopmode}
 %D \stoptyping
 
-\mutable\let\askedlanguage      \empty
-\mutable\let\currentlanguage    \empty
-\mutable\let\currentmainlanguage\empty
+\mutable\lettonothing\askedlanguage
+\mutable\lettonothing\currentlanguage
+\mutable\lettonothing\currentmainlanguage
 
 %D \macros
 %D   {defaultlanguage,languageparameter,specificlanguageparameter}
@@ -191,7 +191,7 @@
 
 % \language[#1] gave unwanted side effect of loading language specifics
 
-\mutable\let\currentsetuplanguage\empty
+\mutable\lettonothing\currentsetuplanguage
 
 \permanent\tolerant\protected\def\installlanguage[#1]#*[#2]%
   {\ifcondition\validassignment{#2}%
@@ -544,7 +544,7 @@
 
 %D You can setup the default language to reset settings.
 
-\mutable\let\currentlanguagesetups\empty
+\mutable\lettonothing\currentlanguagesetups
 
 \appendtoks
     \edef\currentlanguagesetups{\languageparameter\c!setups}%
diff --git a/tex/context/base/mkxl/lang-lab.mkxl b/tex/context/base/mkxl/lang-lab.mkxl
index 2a42861cd..a1d758f09 100644
--- a/tex/context/base/mkxl/lang-lab.mkxl
+++ b/tex/context/base/mkxl/lang-lab.mkxl
@@ -60,7 +60,7 @@
 
 \installcorenamespace{label}
 
-% \let\currentlabelcategory\empty
+% \lettonothing\currentlabelcategory
 
 \permanent\tolerant\protected\def\definelabelclass[#1]#*[#2]%
   {\normalexpanded
@@ -77,12 +77,13 @@
 
 % hm, not interfaced
 
-\mutable\let\thetextprefix\empty
+\mutable\lettonothing\thetextprefix
 
 \mutable\let\currenttextprefixclass\s!unknown
-\mutable\let\currenttextprefixname \empty
 \mutable\let\currenttextprefixtag  \s!unknown
 
+\mutable\lettonothing\currenttextprefixname
+
 \protected\def\lang_labels_define_class_indeed#1#2#3#4#5#6#7#8#9%
   {\permanent\instance\protected\defcsname  setup#1text\endcsname{\protecttextprefixes      #2\def\currenttextprefixclass{#1}\lang_labels_text_prefix_setup}%
    \permanent\instance\protected\defcsname preset#1text\endcsname{\protecttextprefixes\plusone\def\currenttextprefixclass{#1}\lang_labels_text_prefix_setup}%
@@ -223,8 +224,8 @@
      \expandafter\lang_labels_text_prefix_assign_dumb
    \fi{#1}}
 
-\let\m_lang_labels_left \empty
-\let\m_lang_labels_right\empty
+\lettonothing\m_lang_labels_left
+\lettonothing\m_lang_labels_right
 
 \def\lang_labels_text_prefix_assign_yes#1[#2,#3,#4]%
   {\def\m_lang_labels_left {#2}% no longer an edef ... else \Word undefined expansion issues
diff --git a/tex/context/base/mkxl/lang-url.mkxl b/tex/context/base/mkxl/lang-url.mkxl
index 87e64feaf..2d41c6c32 100644
--- a/tex/context/base/mkxl/lang-url.mkxl
+++ b/tex/context/base/mkxl/lang-url.mkxl
@@ -64,8 +64,8 @@
     \enforced\let\Ux\eUx
 \to \everyhyphenatedurl
 
-\mutable\let\hyphenatedurlseparator    \empty % \periodcentered
-\mutable\let\hyphenatedurldiscretionary\empty
+\mutable\lettonothing\hyphenatedurlseparator     % \periodcentered
+\mutable\lettonothing\hyphenatedurldiscretionary
 
 \setnewconstant\hyphenatedurllefthyphenmin \plusthree
 \setnewconstant\hyphenatedurlrighthyphenmin\plusthree
diff --git a/tex/context/base/mkxl/math-ali.mkxl b/tex/context/base/mkxl/math-ali.mkxl
index a2b09a084..6c0fb6b82 100644
--- a/tex/context/base/mkxl/math-ali.mkxl
+++ b/tex/context/base/mkxl/math-ali.mkxl
@@ -395,7 +395,7 @@
 
 \protected\def\math_alignment_lbox#1%
   {\begingroup
-   \setbox\scratchbox\hbox{\letformulaparameter\c!location\empty#1}%
+   \setbox\scratchbox\hbox{\resetformulaparameter\c!location#1}%
    \ifzeropt\wd\scratchbox\else
     %\enablematrixalign
      \hpack
@@ -409,7 +409,7 @@
 
 \protected\def\math_alignment_rbox#1%
   {\begingroup
-   \setbox\scratchbox\hbox{\letformulaparameter\c!location\empty#1}%
+   \setbox\scratchbox\hbox{\resetformulaparameter\c!location#1}%
    \ifzeropt\wd\scratchbox\else
     %\enablematrixalign
      \hpack
@@ -1499,11 +1499,12 @@
 
 \defcsname\??mathmatrixrulealternative\v!auto\endcsname#1#2%
   {\math_matrix_hrule_progress{#1}%
-   \ifnum\c_math_matrix_first=\zerocount
-     \kern-\dimexpr\linewidth\relax
-   \else
-     \kern-\dimexpr.5\d_math_eqalign_distance+\linewidth\relax
-   \fi
+ % \ifzero\c_math_matrix_first
+ %   \kern-\dimexpr\linewidth\relax
+ % \else
+ %   \kern-\dimexpr.5\d_math_eqalign_distance+\linewidth\relax
+ % \fi
+   \kern-\dimexpr\ifzero\c_math_matrix_first\else.5\d_math_eqalign_distance+\fi\linewidth\relax
    \math_matrix_horizontal_rule_yes{#2}%
    %boundary\c_math_matrix_sl_boundary
    \enforced\let\NR\math_matrix_NL_NR}
@@ -1720,8 +1721,8 @@
 
 \installcorenamespace{mathmatrixalignlocation}
 
-\mutable\let\mathmatrixleft \empty % experimental hook
-\mutable\let\mathmatrixright\empty % experimental hook
+\mutable\lettonothing\mathmatrixleft  % experimental hook
+\mutable\lettonothing\mathmatrixright % experimental hook
 
 \defcsname\??mathmatrixalignlocation\v!top   \endcsname{\raise\dimexpr(\nextboxdp-\nextboxht)/2 +\mathaxisheight\mathstyle\relax}
 \defcsname\??mathmatrixalignlocation\v!high  \endcsname{\raise\dimexpr(\nextboxdp-\nextboxht)/2\relax}
@@ -2307,7 +2308,7 @@
 
 \def\strc_math_flush_box_framed_fit_inline
   {\let\currentformulaframed\currentformula
-   \letformulaframedparameter\c!location\empty
+   \resetformulaframedparameter\c!location
    \letformulaframedparameter\c!width\v!fit
    \strc_math_flush_box_framed_common}
 
diff --git a/tex/context/base/mkxl/math-del.mklx b/tex/context/base/mkxl/math-dld.mklx
index 0377f3507..33849e723 100644
--- a/tex/context/base/mkxl/math-del.mklx
+++ b/tex/context/base/mkxl/math-dld.mklx
@@ -1,5 +1,5 @@
 %D \module
-%D   [       file=math-del,
+%D   [       file=math-dld,
 %D        version=2022.07.29,
 %D          title=\CONTEXT\ Math Macros,
 %D       subtitle=delimiteds,
@@ -46,7 +46,7 @@
     \frozen\protected\instance\edefcsname\currentmathdelimited\endcsname{\math_delimited_handle{\currentmathdelimited}}
 \to \everydefinemathdelimited
 
-\mutable\let\currentmathdelimited\empty
+\mutable\lettonothing\currentmathdelimited
 
 \tolerant\protected\def\math_delimited_handle#tag#*[#settings]#:#body%
   {\begingroup
diff --git a/tex/context/base/mkxl/math-fen.mkxl b/tex/context/base/mkxl/math-fen.mkxl
index 1efc6bbe6..69be6adca 100644
--- a/tex/context/base/mkxl/math-fen.mkxl
+++ b/tex/context/base/mkxl/math-fen.mkxl
@@ -399,7 +399,7 @@
    \setfalse\c_math_fenced_level_mode
    \c_attr_mathsize\attributeunsetvalue
    %
-   \letmathfenceparameter\c!size\empty
+   \resetmathfenceparameter\c!size
    \letmathfenceparameter\c!factor\v!auto
    % so far
    \ifparameter#2\or
diff --git a/tex/context/base/mkxl/math-ini.mkxl b/tex/context/base/mkxl/math-ini.mkxl
index 5fcd232a2..480a56642 100644
--- a/tex/context/base/mkxl/math-ini.mkxl
+++ b/tex/context/base/mkxl/math-ini.mkxl
@@ -1968,7 +1968,7 @@
 
 \protected\def\math_function_handle#1#2#3%
   {\begingroup
-   \letdummyparameter\c!mathlimits\empty
+   \resetdummyparameter\c!mathlimits
    \getdummyparameters[#1]%
    \edef\p_limits{\dummyparameter\c!mathlimits}%
    \mathatom
diff --git a/tex/context/base/mkxl/math-rad.mklx b/tex/context/base/mkxl/math-rad.mklx
index 9dfc80d13..645d32740 100644
--- a/tex/context/base/mkxl/math-rad.mklx
+++ b/tex/context/base/mkxl/math-rad.mklx
@@ -101,8 +101,8 @@
     \frozen\protected\instance\edefcsname\currentmathradical\endcsname{\math_radical_handle{\currentmathradical}}
 \to \everydefinemathradical
 
-\mutable\let\currentmathradical      \empty
-\mutable\let\currentmathradicaldegree\empty
+\mutable\lettonothing\currentmathradical
+\mutable\lettonothing\currentmathradicaldegree
 
 \setmathignore\Umathradicaldegreebefore\plusone
 
diff --git a/tex/context/base/mkxl/math-stc.mklx b/tex/context/base/mkxl/math-stc.mklx
index 828115f83..8eb9d59ad 100644
--- a/tex/context/base/mkxl/math-stc.mklx
+++ b/tex/context/base/mkxl/math-stc.mklx
@@ -215,9 +215,9 @@
 %D First we implement the helper that deals with an extensible in the middle and
 %D top and|/|or bottom texts:
 
-\let\m_math_stackers_text_top   \empty
-\let\m_math_stackers_text_bottom\empty
-\let\m_math_stackers_text_middle\empty
+\lettonothing\m_math_stackers_text_top
+\lettonothing\m_math_stackers_text_bottom
+\lettonothing\m_math_stackers_text_middle
 
 \def\math_stackers_flushtext#command#text%
   {\ifdim\scratchleftoffset >\zeropoint\math_stackers_skip\scratchleftoffset \fi
diff --git a/tex/context/base/mkxl/meta-ini.mkxl b/tex/context/base/mkxl/meta-ini.mkxl
index 55a0d8043..bd4445a2f 100644
--- a/tex/context/base/mkxl/meta-ini.mkxl
+++ b/tex/context/base/mkxl/meta-ini.mkxl
@@ -368,15 +368,15 @@
 \permanent\protected\def\finalizeMPdrawing
   {\MPdrawingdonetrue}
 
-\mutable\let\MPdrawingdata\empty
+\mutable\lettonothing\MPdrawingdata
 
 \permanent\protected\def\resetMPdrawing
-  {\glet\MPdrawingdata\empty
+  {\glettonothing\MPdrawingdata
    \global\MPdrawingdonefalse}
 
 \permanent\protected\def\pushMPdrawing
   {\globalpushmacro\MPdrawingdata
-   \glet\MPdrawingdata\empty}
+   \glettonothing\MPdrawingdata}
 
 \permanent\protected\def\popMPdrawing
   {\globalpopmacro\MPdrawingdata}
@@ -415,7 +415,7 @@
 \mutable\def\width {0 } % left-over, obsolete
 \mutable\def\height{0 } % left-over, obsolete
 
-\mutable\let\currentMPclip\empty
+\mutable\lettonothing\currentMPclip
 
 \protected\def\meta_grab_clip_path#1#2#3%
   {\begingroup
@@ -496,7 +496,7 @@
 %D Currently the inheritance of backgrounds does not work and we might drop it
 %D anyway (too messy)
 
-\let\m_meta_current_variable\empty
+\lettonothing\m_meta_current_variable
 
 \installbasicnativeautosetuphandler \??mpcategory {mpcategory}
 
@@ -681,7 +681,7 @@
 
 \def\meta_uniquempgraphic_yes[#1]#*#=%
   {% ugly code but we run on top of older code
-   \letdummyparameter\c!instance\empty
+   \resetdummyparameter\c!instance
    \getdummyparameters[#1]%
    \edef\currentMPinstance{\dummyparameter\c!instance}%
    % here we feed the instance into the analyzer
@@ -757,7 +757,7 @@
 %    \orelse\ifcsname\??mpgraphic\currentMPgraphicname\endcsname
 %      \let\currentmpcategory\currentMPgraphicname
 %    \else
-%      \let\currentmpcategory\empty
+%      \lettonothing\currentmpcategory
 %    \fi
 %    \ifempty\currentmpcategory
 %      % message
@@ -773,7 +773,7 @@
 
 \def\meta_usempgraphic_yes[#1]#*#=%
   {% ugly code but we run on top of older code
-   \letdummyparameter\c!instance\empty
+   \resetdummyparameter\c!instance
    \getdummyparameters[#1]%
    \edef\currentMPinstance{\dummyparameter\c!instance}%
    % here we feed the instance into the analyzer
@@ -783,7 +783,7 @@
    \orelse\ifcsname\??mpgraphic\currentMPgraphicname\endcsname
      \let\currentmpcategory\currentMPgraphicname
    \else
-     \let\currentmpcategory\empty
+     \lettonothing\currentmpcategory
    \fi
    \ifempty\currentmpcategory
      % message
@@ -801,7 +801,7 @@
    \orelse\ifcsname\??mpgraphic\currentMPgraphicname\endcsname
      \let\currentmpcategory\currentMPgraphicname
    \else
-     \let\currentmpcategory\empty
+     \lettonothing\currentmpcategory
    \fi
    \ifempty\currentmpcategory
      % message
@@ -973,7 +973,7 @@
 %    \ifempty\currentMPinstance
 %      \let\currentMPinstance\defaultMPinstance
 %    \fi
-%    \let\currentMPgraphicname\empty
+%    \lettonothing\currentMPgraphicname
 %    \edef\currentMPformat{\MPinstanceparameter\s!format}%
 %    \meta_enable_include
 %    \meta_process_graphic{#2}%
@@ -988,7 +988,7 @@
    \ifempty\currentMPinstance
      \let\currentMPinstance\defaultMPinstance
    \fi
-   \let\currentMPgraphicname\empty
+   \lettonothing\currentMPgraphicname
    \edef\currentMPformat{\MPinstanceparameter\s!format}%
    \meta_enable_include
    \meta_process_graphic{#2}%
@@ -996,15 +996,15 @@
 
 \def\meta_start_mpcode_yes[#1]#2\stopMPcode
   {\begingroup
-   \letdummyparameter\c!instance\empty
-   \letdummyparameter\c!stacking\empty
+   \resetdummyparameter\c!instance
+   \resetdummyparameter\c!stacking
    \getdummyparameters[#1]%
    \edef\currentMPinstance{\dummyparameter\c!instance}%
    \setmpcategoryparameter\c!stacking{\dummyparameter\c!stacking}%
    \ifempty\currentMPinstance
      \let\currentMPinstance\defaultMPinstance
    \fi
-   \let\currentMPgraphicname\empty
+   \lettonothing\currentMPgraphicname
    \edef\currentMPformat{\MPinstanceparameter\s!format}%
    \meta_enable_include
    \meta_process_graphic{#2}%
@@ -1105,17 +1105,17 @@
 
 % \setupcolors[state=stop,conversion=never] % quite tricky ... type mismatch
 
-\startMPinitializations
-    CurrentLayout:="\currentlayout";
-\stopMPinitializations
+% \startMPinitializations
+%     CurrentLayout:="\currentlayout";
+% \stopMPinitializations
 
 %D A dirty trick, ** in colo-ini.lua (mpcolor). We cannot use a vardef, because
 %D that fails with spot colors.
 
-\startMPinitializations
-    def OverlayLineColor=\ifempty\overlaylinecolor black \else\MPcolor{\overlaylinecolor} \fi enddef;
-    def OverlayColor    =\ifempty\overlaycolor     black \else\MPcolor{\overlaycolor}     \fi enddef;
-\stopMPinitializations
+% \startMPinitializations
+%     def OverlayLineColor=\ifempty\overlaylinecolor black \else\MPcolor{\overlaylinecolor} \fi enddef;
+%     def OverlayColor    =\ifempty\overlaycolor     black \else\MPcolor{\overlaycolor}     \fi enddef;
+% \stopMPinitializations
 
 \appendtoks
     \disablediscretionaries
@@ -1367,7 +1367,7 @@
    \ifempty\currentMPinstance
      \let\currentMPinstance\defaultMPinstance
    \fi
-   \let\currentMPgraphicname\empty
+   \lettonothing\currentMPgraphicname
    \edef\currentMPformat{\MPinstanceparameter\s!format}%
    \meta_enable_include
    \meta_process_graphic{#2;draw origin}%
@@ -1398,8 +1398,8 @@
 
 %D Some more helpers (see \type {meta-grd.mkiv} for an example of usage):
 
-\permanent\def\MPdpar#1#2{\the\dimexpr#1#2\relax\empty}
-\permanent\def\MPnpar#1#2{\the\numexpr#1#2\relax\empty}
+\permanent\def\MPdpar#1#2{\the\dimexpr#1#2\relax\empty} % why \empty here
+\permanent\def\MPnpar#1#2{\the\numexpr#1#2\relax\empty} % why \empty here
 \permanent\def\MPspar#1#2{"#1#2"}
 
 %D Done.
diff --git a/tex/context/base/mkxl/meta-pdf.mkxl b/tex/context/base/mkxl/meta-pdf.mkxl
index 32f53ceb3..8dc0bdfac 100644
--- a/tex/context/base/mkxl/meta-pdf.mkxl
+++ b/tex/context/base/mkxl/meta-pdf.mkxl
@@ -34,7 +34,7 @@
 %D graphics. The color control flags are also gone as we now integrate into the
 %D regular colorspace handling (i.e.\ no longer independent configurations.)
 
-\mutable\let\MPfilename\empty
+\mutable\lettonothing\MPfilename
 
 \permanent\protected\def\convertMPtoPDF#1#2#3% scaling no longer supported at this level (so #2 & #3 are ignored)
   {\dostarttagged\t!mpgraphic\empty
diff --git a/tex/context/base/mkxl/meta-pdh.mkxl b/tex/context/base/mkxl/meta-pdh.mkxl
index b748682a7..0313d0669 100644
--- a/tex/context/base/mkxl/meta-pdh.mkxl
+++ b/tex/context/base/mkxl/meta-pdh.mkxl
@@ -84,9 +84,10 @@
 \ifdefined\makeMPintoPDFobject    \else \newconstant\makeMPintoPDFobject    \fi
 \ifdefined\everyMPtoPDFconversion \else \newtoks    \everyMPtoPDFconversion \fi
 
-\let\lastPDFMPobject    \!!zerocount
-\let\currentPDFresources\empty
-\let\setMPextensions    \relax
+\let\lastPDFMPobject\!!zerocount
+\let\setMPextensions\relax
+
+\lettonothing\currentPDFresources
 
 \def\PDFMPformoffset{\ifdefined\objectoffset\objectoffset\else\zeropoint\fi} % no longer used
 
@@ -139,7 +140,7 @@
 
 %D A common hook.
 
-\let\MPfshowcommand\empty
+\lettonothing\MPfshowcommand
 
 %D Objects.
 
diff --git a/tex/context/base/mkxl/mlib-int.lmt b/tex/context/base/mkxl/mlib-int.lmt
index 47560e8c4..ea9092611 100644
--- a/tex/context/base/mkxl/mlib-int.lmt
+++ b/tex/context/base/mkxl/mlib-int.lmt
@@ -187,8 +187,10 @@ do
     local d_overlay_depth     = isdimen("d_overlay_depth")     registerdirect("OverlayDepth",     function() return getdimen(d_overlay_depth)     * factor end)
     local d_overlay_linewidth = isdimen("d_overlay_linewidth") registerdirect("OverlayLineWidth", function() return getdimen(d_overlay_linewidth) * factor end)
     local d_overlay_offset    = isdimen("d_overlay_offset")    registerdirect("OverlayOffset",    function() return getdimen(d_overlay_offset)    * factor end)
-                                                               registerdirect("OverlayRegion",    function() return getmacro("m_overlay_region")              end)
-                                                               --------------("CurrentLayout",    function() return getmacro("currentlayout")                 end)
+                                                               registerdirect("OverlayRegion",    function() return getmacro("m_overlay_region")           end)
+                                                               registerdirect("CurrentLayout",    function() return getmacro("currentlayout")              end)
+                                                               registerdirect("OverlayColor",     function() return getmacro("overlaycolor")               end)
+                                                               registerdirect("OverlayLineColor", function() return getmacro("overlaylinecolor")               end)
 
 end
 
diff --git a/tex/context/base/mkxl/mult-aux.mkxl b/tex/context/base/mkxl/mult-aux.mkxl
index f387bf95d..93d1113a3 100644
--- a/tex/context/base/mkxl/mult-aux.mkxl
+++ b/tex/context/base/mkxl/mult-aux.mkxl
@@ -15,13 +15,19 @@
 %D (interface might change). The code here evolved in an email exchange between me
 %D and Wolgang Schuster.
 
+%D We use constant definitions here because we don't need to expand the keywords
+%D which saves a little on the stack (read: memory access). The gain in performance
+%D is normally not noticeable unless one has plenty of parameter checking, which
+%D can happen in some scenarios. Even then the gain is only there when one has
+%D thousands of runs on e.g. virtual platforms.
+
 \writestatus{loading}{ConTeXt Multilingual Macros / Helpers}
 
 \registerctxluafile{mult-aux}{}
 
 \unprotect
 
-\immutable\edef\??empty{\Uchar25}  \immutable\letvalue{\Uchar25}\empty % hex 19
+\immutable\cdef\??empty{\Uchar25}  \immutable\letvalue{\Uchar25}\empty % hex 19
 
 % \edef\s!parent{\Uchar29} % inlining  is ugly, a tiny bit faster, but neglectable on a run
 
@@ -84,7 +90,7 @@
 
 % KEEP THIS:
 %
-% \let\m_mult_interfaces_namespace\empty
+% \lettonothing\m_mult_interfaces_namespace
 %
 % \def\mult_interfaces_get_parameters#1[#2%
 %   {\if\noexpand#2]%
@@ -172,7 +178,7 @@
 %D a comma and trigger a warning but we intercept that elsewhere. The alternative is
 %D to skip to the comma first which takes more time.
 
-\let\m_mult_interfaces_namespace\empty
+\lettonothing\m_mult_interfaces_namespace
 
 \def\mult_interfaces_get_parameters#1[%
   {\def\m_mult_interfaces_namespace{#1}%
@@ -355,8 +361,8 @@
 \mutable\let\dousecurrentstyleparameter\relax
 \mutable\let\dousecurrentcolorparameter\relax
 
-\mutable\let\currentstyleparameter\empty
-\mutable\let\currentcolorparameter\empty
+\mutable\lettonothing\currentstyleparameter
+\mutable\lettonothing\currentcolorparameter
 
 % maybe we should have \names ones too
 
@@ -402,35 +408,35 @@
      {\let#8#4%
       % watch out: no \edef#4{##1} before the ifarguments because #1 can have macros
       \ifarguments
-        \let#4\empty
+        \lettonothing#4%
         \the#5% predefine
-        \let#7\empty
+        \lettonothing#7%
         \letcsname#1#4:\s!chain\endcsname\empty
-        \edefcsname#1#4:\s!parent\endcsname{#3}%
+        \cdefcsname#1#4:\s!parent\endcsname{#3}%
       \or
         \edef#4{##1}%
         \the#5% predefine
-        \let#7\empty
-        \edefcsname#1#4:\s!chain\endcsname{##1}%
-        \edefcsname#1#4:\s!parent\endcsname{#3}%
+        \lettonothing#7%
+        \cdefcsname#1#4:\s!chain\endcsname{##1}%
+        \cdefcsname#1#4:\s!parent\endcsname{#3}%
       \or
         \edef#4{##1}%
         \the#5% predefine
         \relax
         \ifhastok={##2}%
-          \let#7\empty
-          \edefcsname#1#4:\s!chain\endcsname{##1}%
-          \edefcsname#1#4:\s!parent\endcsname{#3}%
+          \lettonothing#7%
+          \cdefcsname#1#4:\s!chain\endcsname{##1}%
+          \cdefcsname#1#4:\s!parent\endcsname{#3}%
           \mult_interfaces_get_parameters{#1#4:}[##2]%
         \else
           \edef#7{##2}%
           \ifempty#7%
-            \edefcsname#1#4:\s!chain\endcsname{##1}%
-            \edefcsname#1#4:\s!parent\endcsname{#3}%
+            \cdefcsname#1#4:\s!chain\endcsname{##1}%
+            \cdefcsname#1#4:\s!parent\endcsname{#3}%
           \else
             \mult_check_for_parent{#1}{#3}#4#7%
-            \edefcsname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
-            \edefcsname#1#4:\s!parent\endcsname{#1##2}%
+            \cdefcsname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
+            \cdefcsname#1#4:\s!parent\endcsname{#1##2}%
           \fi
         \fi
       \or
@@ -438,8 +444,8 @@
         \the#5% predefine
         \edef#7{##2}%
         \mult_check_for_parent{#1}{#3}#4#7%
-        \edefcsname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
-        \edefcsname#1#4:\s!parent\endcsname{#1##2}%
+        \cdefcsname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
+        \cdefcsname#1#4:\s!parent\endcsname{#1##2}%
         \mult_interfaces_get_parameters{#1#4:}[##3]%
       \fi
       \the#6%
@@ -472,7 +478,7 @@
            \the#4}%
         \processcommalist[##1]#8%
       \else
-        \let#3\empty
+        \lettonothing#3%
         \mult_interfaces_get_parameters{#1:}[##1]%
         \the#4%
       \fi
@@ -509,7 +515,7 @@
      {\ifarguments
         % \setuplayout
         \let#6#3%      % previous becomes current
-        \let#3\empty   % current becomes empty
+        \lettonothing#3%   % current becomes empty
         #2\doingrootsetroot
         \the#5%
         \the#8% switchsetups
@@ -518,7 +524,7 @@
           % \setuplayout[key=value]
           \let#7#3%
           \let#6#3%
-          \let#3\empty
+          \lettonothing#3%
           #2\doingrootsetuproot
           \mult_interfaces_get_parameters{#1:}[##1]%
           \the#5%
@@ -579,10 +585,10 @@
    \frozen\tolerant\protected\def#2[##1]##*[##2]##*[##3]%
      {\let#7#3%
       \ifarguments
-        \let#3\empty
+        \lettonothing#3%
         \the#4%
       \or
-        \let#3\empty
+        \lettonothing#3%
         \mult_interfaces_get_parameters{#1:}[##1]%
         \the#4%
       \or
@@ -757,17 +763,17 @@
   {\frozen\tolerant\protected\defcsname#1\endcsname[##1]##*[##2]%
      {\begingroup
       \ifarguments
-        \let#2\empty
+        \lettonothing#2%
       \or
        %\ifcondition\expandafter\mult_check_for_assignment_indeed_begin_\detokenize{##1}=^^^^0003^^^^0003^^^^0004%
       % \ifcondition\mult_aux_no_assignment_indeed##1\ignorearguments
       %   \edef#2{##1}%
       % \else
-      %   \let#2\empty
+      %   \lettonothing#2%
       %   #3[##1]%
       % \fi
         \ifhastok={##1}%
-          \let#2\empty
+          \lettonothing#2%
           #3[##1]%
         \else
           \edef#2{##1}%
@@ -825,7 +831,7 @@
      \writestatus\m!system{duplicate user namespace '#1'}\wait
    \else
      \global\advance\c_mult_interfaces_n_of_namespaces\plusone
-     \immutable\xdefcsname ????#1\endcsname{\v_interfaces_prefix_template}%
+     \global\immutable\cdefcsname ????#1\endcsname{\v_interfaces_prefix_template}%
    \fi}
 
 \permanent\protected\def\installcorenamespace#1%
@@ -833,7 +839,7 @@
      \writestatus\m!system{duplicate core namespace '#1'}\wait
    \else
      \global\advance\c_mult_interfaces_n_of_namespaces\plusone
-     \immutable\xdefcsname ??#1\endcsname{\v_interfaces_prefix_template}%
+     \global\immutable\cdefcsname ??#1\endcsname{\v_interfaces_prefix_template}%
      \clf_registernamespace\c_mult_interfaces_n_of_namespaces{#1}%
    \fi}
 
@@ -858,6 +864,7 @@
 \permanent\protected\def\setdummyparameter        #1{\defcsname\??dummy#1\endcsname}
 \permanent\protected\def\setexpandeddummyparameter#1{\edefcsname\??dummy#1\endcsname}
 \permanent\protected\def\letdummyparameter        #1{\letcsname\??dummy#1\endcsname}
+\permanent\protected\def\resetdummyparameter      #1{\letcsname\??dummy#1\endcsname\empty}
 
 \edef\mult_interfaces_dummy{\??dummy} % nor immutable
 
@@ -1006,7 +1013,7 @@
 
 \protected\def\mult_interfaces_install_definition_set#1#2#3#4#5#6#7%
   {\newcount#3%
-   \let#6\empty
+   \lettonothing#6%
    \protected\def#2%
      {\expandafter\let\expandafter\c_mult_set\csname #1_t_#6\endcsname
       \ifrelax\c_mult_set
@@ -1197,10 +1204,10 @@
        \frozen\tolerant\protected\def#2[##1]##*[##2]##*[##3]%
          {\let#7#3%
           \ifarguments
-            \let#3\empty
+            \lettonothing#3%
             \the#4%
           \or
-            \let#3\empty
+            \lettonothing#3%
             \let\mult_interfaces_adef\mult_interfaces_adef_nop
             \mult_interfaces_get_parameters{#1:}[##1]%
             \let\mult_interfaces_adef\mult_interfaces_adef_yes
diff --git a/tex/context/base/mkxl/mult-ini.lmt b/tex/context/base/mkxl/mult-ini.lmt
index 7c60d5b33..a58e60059 100644
--- a/tex/context/base/mkxl/mult-ini.lmt
+++ b/tex/context/base/mkxl/mult-ini.lmt
@@ -17,7 +17,7 @@ local implement           = interfaces.implement
 
 local allocate            = utilities.storage.allocate
 local mark                = utilities.storage.mark
-local prtcatcodes         = catcodes.numbers.prtcatcodes
+----- prtcatcodes         = catcodes.numbers.prtcatcodes
 local vrbcatcodes         = catcodes.numbers.vrbcatcodes
 local contextsprint       = context.sprint
 local setmetatableindex   = table.setmetatableindex
diff --git a/tex/context/base/mkxl/mult-ini.mkxl b/tex/context/base/mkxl/mult-ini.mkxl
index b357c3e12..0e010429e 100644
--- a/tex/context/base/mkxl/mult-ini.mkxl
+++ b/tex/context/base/mkxl/mult-ini.mkxl
@@ -55,14 +55,14 @@
 %D \type {!!!!}. In the meantime some of these are obsolete (we had some 12
 %D originally).
 
-\immutable\def\c!prefix!{c!}
-\immutable\def\k!prefix!{k!}
-\immutable\def\e!prefix!{e!}
-\immutable\def\f!prefix!{f!} % for the moment we keep this one
-\immutable\def\m!prefix!{m!}
-\immutable\def\s!prefix!{s!}
-\immutable\def\v!prefix!{v!}
-\immutable\def\t!prefix!{t!}
+\immutable\cdef\c!prefix!{c!}
+\immutable\cdef\k!prefix!{k!}
+\immutable\cdef\e!prefix!{e!}
+\immutable\cdef\f!prefix!{f!} % for the moment we keep this one
+\immutable\cdef\m!prefix!{m!}
+\immutable\cdef\s!prefix!{s!}
+\immutable\cdef\v!prefix!{v!}
+\immutable\cdef\t!prefix!{t!}
 
 %D \macros
 %D   [constants,variables,commands]
@@ -73,22 +73,22 @@
 %D \type {??}, and a system constant, which has the prefix \type {c!}. We'll se some
 %D more of this.
 
-\immutable\def\??prefix  {??}
-\immutable\def\@@prefix  {@@}
+\immutable\cdef\??prefix  {??}
+\immutable\cdef\@@prefix  {@@}
 
 %D Just to be complete we repeat some of the already defined system constants here.
 %D Maybe their prefix \type {\s!} now falls into place.
 
-\def\s!next    {next}         \def\s!default {default}
-\def\s!dummy   {dummy}        \def\s!unknown {unknown}
+\cdef\s!next    {next}         \cdef\s!default {default}
+\cdef\s!dummy   {dummy}        \cdef\s!unknown {unknown}
 
-\def\s!do      {do}           \def\s!dodo    {dodo}
+\cdef\s!do      {do}           \cdef\s!dodo    {dodo}
 
-\def\s!complex {complex}      \def\s!start   {start}
-\def\s!simple  {simple}       \def\s!stop    {stop}
+\cdef\s!complex {complex}      \cdef\s!start   {start}
+\cdef\s!simple  {simple}       \cdef\s!stop    {stop}
 
-\def\s!true    {true}
-\def\s!false   {false}
+\cdef\s!true    {true}
+\cdef\s!false   {false}
 
 %D The word \type {height} takes 6~token memory cells. The control sequence \type
 %D {\height} on the other hand uses only one. Knowing this, we can improve the
@@ -109,32 +109,32 @@
 %D than once. Savings like this should of course be implemented in english, just
 %D because \TEX\ is english.
 
-\def\s!width      {width}
-\def\s!height     {height}
-\def\s!depth      {depth}
-\def\s!spread     {spread}
-\def\s!plus       {plus}
-\def\s!minus      {minus}
-\def\s!to         {to}
-
-\def\s!fil        {fil}
-\def\s!fill       {fill}
-\def\s!filll      {filll}
-
-\def\s!attr       {attr}
-\def\s!axis       {axis}
-\def\s!both       {both}
-\def\s!bottom     {bottom}
-\def\s!left       {left}
-\def\s!options    {options}
-\def\s!orientation{orientation}
-\def\s!reverse    {reverse}
-\def\s!right      {right}
-\def\s!top        {top}
-\def\s!xmove      {xmove}
-\def\s!xoffset    {xoffset}
-\def\s!ymove      {ymove}
-\def\s!yoffset    {yoffset}
+\cdef\s!width      {width}
+\cdef\s!height     {height}
+\cdef\s!depth      {depth}
+\cdef\s!spread     {spread}
+\cdef\s!plus       {plus}
+\cdef\s!minus      {minus}
+\cdef\s!to         {to}
+
+\cdef\s!fil        {fil}
+\cdef\s!fill       {fill}
+\cdef\s!filll      {filll}
+
+\cdef\s!attr       {attr}
+\cdef\s!axis       {axis}
+\cdef\s!both       {both}
+\cdef\s!bottom     {bottom}
+\cdef\s!left       {left}
+\cdef\s!options    {options}
+\cdef\s!orientation{orientation}
+\cdef\s!reverse    {reverse}
+\cdef\s!right      {right}
+\cdef\s!top        {top}
+\cdef\s!xmove      {xmove}
+\cdef\s!xoffset    {xoffset}
+\cdef\s!ymove      {ymove}
+\cdef\s!yoffset    {yoffset}
 
 %D \macros
 
@@ -171,9 +171,9 @@
 %D \def\e!name{meaning}
 %D \stoptyping
 
-%permanent\protected\def\defineinterfaceconstant#1#2{\immutable\defcsname\c!prefix!#1\endcsname{#2}}
-\permanent\protected\def\defineinterfacevariable#1#2{\immutable\defcsname\v!prefix!#1\endcsname{#2}}
-\permanent\protected\def\defineinterfaceelement #1#2{\immutable\defcsname\e!prefix!#1\endcsname{#2}}
+%permanent\protected\def\defineinterfaceconstant#1#2{\immutable\cdefcsname\c!prefix!#1\endcsname{#2}}
+\permanent\protected\def\defineinterfacevariable#1#2{\immutable\cdefcsname\v!prefix!#1\endcsname{#2}}
+\permanent\protected\def\defineinterfaceelement #1#2{\immutable\cdefcsname\e!prefix!#1\endcsname{#2}}
 
 %D Next come some interface independant constants:
 %D
@@ -181,7 +181,7 @@
 %D \definefileconstant      {name} {meaning}
 %D \stoptyping
 
-\permanent\protected\def\definefileconstant#1#2{\immutable\defcsname\f!prefix!#1\endcsname{#2}}
+\permanent\protected\def\definefileconstant#1#2{\immutable\cdefcsname\f!prefix!#1\endcsname{#2}}
 
 %D And finaly we have the one argument, space saving constants
 %D
@@ -190,13 +190,13 @@
 %D \definemessageconstant {name}
 %D \stoptyping
 
-\permanent\protected\def\definesystemconstant #1{\immutable\defcsname\s!prefix!#1\endcsname{#1}}
-\permanent\protected\def\definemessageconstant#1{\immutable\defcsname\m!prefix!#1\endcsname{#1}}
+\permanent\protected\def\definesystemconstant #1{\immutable\cdefcsname\s!prefix!#1\endcsname{#1}}
+\permanent\protected\def\definemessageconstant#1{\immutable\cdefcsname\m!prefix!#1\endcsname{#1}}
 
 %D For now here:
 
-\permanent\protected\def\definetagconstant  #1{\immutable\defcsname\t!prefix!#1\endcsname{#1}}
-\permanent\protected\def\aliastagconstant #1#2{\aliased  \letcsname\t!prefix!#1\expandafter\endcsname\csname\t!prefix!#2\endcsname}
+\permanent\protected\def\definetagconstant  #1{\immutable\cdefcsname\t!prefix!#1\endcsname{#1}}
+\permanent\protected\def\aliastagconstant #1#2{\aliased   \letcsname\t!prefix!#1\expandafter\endcsname\csname\t!prefix!#2\endcsname}
 
 %D In a parameter driven system, some parameters are shared by more system
 %D components. In \CONTEXT\ we can distinguish parameters by a unique prefix. Such a
@@ -206,7 +206,7 @@
 %D \definesystemvariable {name}
 %D \stoptyping
 
-\permanent\protected\def\definesystemvariable#1{\immutable\edefcsname\??prefix#1\endcsname{\@@prefix#1}}
+\permanent\protected\def\definesystemvariable#1{\immutable\cdefcsname\??prefix#1\endcsname{\@@prefix#1}}
 
 \definesystemvariable{ms}
 
@@ -370,7 +370,7 @@
 
 \aliased\let\stopmessages\relax
 
-\mutable\let\currentmessagetext\empty
+\mutable\lettonothing\currentmessagetext
 
 \permanent\protected\def\setinterfacemessage#1#2#3%
   {\ifcsname\m!prefix!#1\endcsname\else\immutable\gdefcsname\m!prefix!#1\endcsname{#1}\fi
@@ -685,11 +685,11 @@
 
 \permanent\overloaded\protected\def\setinterfaceconstant#1#2%
   {\clf_setinterfaceconstant{#1}{#2}%
-   \immutable\defcsname\c!prefix!#1\endcsname{#1}}
+   \immutable\cdefcsname\c!prefix!#1\endcsname{#1}}
 
 \permanent\overloaded\protected\def\setinterfacevariable#1#2%
   {\clf_setinterfacevariable{#1}{#2}%
-   \immutable\defcsname\v!prefix!#1\endcsname{#2}}
+   \immutable\cdefcsname\v!prefix!#1\endcsname{#2}}
 
 %D \macros
 %D   {defineinterfaceconstant}
@@ -699,7 +699,7 @@
 %D c||version, but for documentation purposes the x||alternative comes in handy.
 
 \permanent\overloaded\protected\def\defineinterfaceconstant#1#2%
-  {\immutable\defcsname\c!prefix!#1\endcsname{#2}}
+  {\immutable\cdefcsname\c!prefix!#1\endcsname{#2}}
 
 %D \macros
 %D   {startelements}
diff --git a/tex/context/base/mkxl/node-ext.mkxl b/tex/context/base/mkxl/node-ext.mkxl
index 697bb7d29..2f0df1ba3 100644
--- a/tex/context/base/mkxl/node-ext.mkxl
+++ b/tex/context/base/mkxl/node-ext.mkxl
@@ -66,7 +66,7 @@
 %D \dostopclipping
 %D \stoptyping
 
-\mutable\let\MPclippath\empty
+\mutable\lettonothing\MPclippath
 
 % \permanent\protected\def\dostartclipping#1#2#3% we can move this to lua and only set a box here
 %   {\forcecolorhack
diff --git a/tex/context/base/mkxl/node-rul.mkxl b/tex/context/base/mkxl/node-rul.mkxl
index ec9003f58..6f62e3022 100644
--- a/tex/context/base/mkxl/node-rul.mkxl
+++ b/tex/context/base/mkxl/node-rul.mkxl
@@ -78,9 +78,9 @@
 
 \installcommandhandler \??bar {bar} \??bar
 
-\mutable\let\p_node_color \empty % of just \p_*
-\mutable\let\p_node_text  \empty
-\mutable\let\p_node_offset\empty
+\mutable\lettonothing\p_node_color  % of just \p_*
+\mutable\lettonothing\p_node_text
+\mutable\lettonothing\p_node_offset
 
 \aliased\let\setupbars\setupbar
 
@@ -298,10 +298,10 @@
 \newdimen\d_rule_offset
 \newdimen\d_rule_factor
 
-\mutable\let\m_rule_direction\empty
-% \mutable\let\m_rule_factor   \empty
-\mutable\let\m_rule_option   \empty
-\mutable\let\m_rule_color    \empty
+\mutable\lettonothing\m_rule_direction
+%mutable\lettonothing\m_rule_factor
+\mutable\lettonothing\m_rule_option
+\mutable\lettonothing\m_rule_color
 
 \startuseMPgraphic{rules:under:random}
     draw
diff --git a/tex/context/base/mkxl/pack-box.mkxl b/tex/context/base/mkxl/pack-box.mkxl
index 7c64b0032..746d225cb 100644
--- a/tex/context/base/mkxl/pack-box.mkxl
+++ b/tex/context/base/mkxl/pack-box.mkxl
@@ -51,7 +51,7 @@
 %
 % \anchor[text-1][preset=lefttop][framed settings]{HELLO WORLD}
 
-\mutable\let\currentanchor\empty
+\mutable\lettonothing\currentanchor
 
 \permanent\tolerant\protected\def\defineanchor[#1]#*[#2]#*[#3]#*[#4]% name targetlayer layersetting framedsetting
   {\defcsname\??anchor#1\endcsname{\pack_anchors_process_defined{#2}{#3}{#4}}}
@@ -359,8 +359,8 @@
         {\box\nextbox}%
       \setcollector
         [caption][#1]%
-        {\letdummyparameter\c!style\empty
-         \letdummyparameter\c!color\empty
+        {\resetdummyparameter\c!style
+         \resetdummyparameter\c!color
          \getdummyparameters[#2]%
          \dousestyleparameter{\directdummyparameter\c!style}%
          \setupinterlinespace
@@ -548,8 +548,8 @@
 \defcsname\??bleedinglocation tr\endcsname{\settrue\c_pack_boxes_r\settrue\c_pack_boxes_t}
 \defcsname\??bleedinglocation rt\endcsname{\settrue\c_pack_boxes_r\settrue\c_pack_boxes_t}
 
-\mutable\let\currentbleedposition\empty
-\mutable\let\currentpageposition \empty
+\mutable\lettonothing\currentbleedposition
+\mutable\lettonothing\currentpageposition
 
 \permanent\tolerant\protected\def\bleed[#1]%
   {\hbox\bgroup
@@ -694,10 +694,10 @@
 
 \permanent\tolerant\protected\def\setlayertext[#1]#*[#2]#*[#3]%
   {\bgroup
-   \letdummyparameter\c!align\empty
-   \letdummyparameter\c!width\hsize
-   \letdummyparameter\c!color\empty
-   \letdummyparameter\c!style\empty
+   \resetdummyparameter\c!align
+   \letdummyparameter  \c!width\hsize
+   \resetdummyparameter\c!color
+   \resetdummyparameter\c!style
    \getdummyparameters[#3]%
    \dowithnextboxcontent
      {\forgetall
@@ -1191,10 +1191,10 @@
             \halfwaytotallistanchorcode
           \fi
         \relax
-      \ifdim\scratchxoffset=\zeropoint\else
+      \ifzeropt\scratchxoffset\else
          \boxxoffset\nextbox\scratchxoffset
       \fi
-      \ifdim\scratchyoffset=\zeropoint\else
+      \ifzeropt\scratchyoffset\else
          \boxyoffset\nextbox\scratchyoffset
       \fi
       \global\setbox\scratchcounterone\hpack\bgroup
@@ -1238,7 +1238,7 @@
 
 \installmacrostack\boxanchoringclass
 
-\mutable\let\boxanchoringclass\empty
+\mutable\lettonothing\boxanchoringclass
 
 \newcount\c_anchor_auto_box_class
 
diff --git a/tex/context/base/mkxl/pack-com.mkxl b/tex/context/base/mkxl/pack-com.mkxl
index 2b751e08b..787fe4d96 100644
--- a/tex/context/base/mkxl/pack-com.mkxl
+++ b/tex/context/base/mkxl/pack-com.mkxl
@@ -228,9 +228,9 @@
 
 \newtoks\everycombination
 
-\aliased\let\combination\empty
+\aliased\lettonothing\combination
 
-\let\p_nx_ny\empty
+\lettonothing\p_nx_ny
 
 % \permanent\tolerant\protected\def\startcombination[#1]#*[#2]% can be simplified
 %   {\bgroup % so we can grab a group
@@ -240,16 +240,16 @@
 %    %
 %    \ifempty\p_nx_ny
 %      \ifcondition\validassignment{#1}%
-%        \let\currentcombination\empty
+%        \lettonothing\currentcombination
 %        \setupcurrentcombination[#1]%
 %        \edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}%
 %      \else
 %        \doifelseinstring{*}\currentcombination
 %          {\edef\p_nx_ny{\currentcombination*\plusone*}%
-%           \let\currentcombination\empty}
+%           \lettonothing\currentcombination}
 %          {\doifelsenumber\currentcombination
 %             {\edef\p_nx_ny{\currentcombination*\plusone*}%
-%              \let\currentcombination\empty}
+%              \lettonothing\currentcombination}
 %             {\edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}}}%
 %      \fi
 %    \else
@@ -265,15 +265,15 @@
 % %
 % %    \ifempty\p_nx_ny
 % %      \ifhastok={#1}%
-% %        \let\currentcombination\empty
+% %        \lettonothing\currentcombination
 % %        \setupcurrentcombination[#1]%
 % %        \edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}%
 % %      \orelse\ifhastok*{\currentcombination}%
 % %        \edef\p_nx_ny{\currentcombination*\plusone*}%
-% %        \let\currentcombination\empty
+% %        \lettonothing\currentcombination
 % %      \orelse\ifchknum\currentcombination\or
 % %        \edef\p_nx_ny{\currentcombination*\plusone*}%
-% %        \let\currentcombination\empty
+% %        \lettonothing\currentcombination
 % %      \else
 % %        \edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}%
 % %      \fi
@@ -303,7 +303,7 @@
 %    %
 %    \dostarttaggedchained\t!combination\currentcombination\??combination
 %    \vbox \ifx\p_height\v!fit\else to \p_height \fi \bgroup
-%    \enforced\let\combination\empty % permits \combination{}{} handy for cld
+%    \enforced\lettonothing\combination % permits \combination{}{} handy for cld
 %    \normalexpanded{\pack_combinations_start_indeed[\p_nx_ny]}}
 %
 % \permanent\protected\def\stopcombination
@@ -332,16 +332,16 @@
    %
    \ifempty\p_nx_ny
      \ifcondition\validassignment{#1}%
-       \let\currentcombination\empty
+       \lettonothing\currentcombination
        \setupcurrentcombination[#1]%
        \edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}%
      \else
        \doifelseinstring{*}\currentcombination
          {\edef\p_nx_ny{\currentcombination*\plusone*}%
-          \let\currentcombination\empty}
+          \lettonothing\currentcombination}
          {\doifelsenumber\currentcombination
             {\edef\p_nx_ny{\currentcombination*\plusone*}%
-             \let\currentcombination\empty}
+             \lettonothing\currentcombination}
             {\edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}}}%
      \fi
    \else
@@ -358,15 +358,15 @@
 %
 %    \ifempty\p_nx_ny
 %      \ifhastok={#1}%
-%        \let\currentcombination\empty
+%        \lettonothing\currentcombination
 %        \setupcurrentcombination[#1]%
 %        \edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}%
 %      \orelse\ifhastok*{\currentcombination}%
 %        \edef\p_nx_ny{\currentcombination*\plusone*}%
-%        \let\currentcombination\empty
+%        \lettonothing\currentcombination
 %      \orelse\ifchknum\currentcombination\or
 %        \edef\p_nx_ny{\currentcombination*\plusone*}%
-%        \let\currentcombination\empty
+%        \lettonothing\currentcombination
 %      \else
 %        \edef\p_nx_ny{\combinationparameter\c!nx*\combinationparameter\c!ny*}%
 %      \fi
@@ -399,7 +399,7 @@
    \ifcsname\??combinationmethod\combinationparameter\c!method\endcsname
      \lastnamedcs\else\vbox
    \fi\ifx\p_height\v!fit\else to \p_height \fi \bgroup
-   \enforced\let\combination\empty % permits \combination{}{} handy for cld
+   \enforced\lettonothing\combination % permits \combination{}{} handy for cld
    \normalexpanded{\pack_combinations_start_indeed[\p_nx_ny]}}
 
 \permanent\protected\def\stopcombination
diff --git a/tex/context/base/mkxl/pack-cut.mkxl b/tex/context/base/mkxl/pack-cut.mkxl
index 1e23a97e3..3f4e6d0c3 100644
--- a/tex/context/base/mkxl/pack-cut.mkxl
+++ b/tex/context/base/mkxl/pack-cut.mkxl
@@ -58,13 +58,14 @@
 \newcount\cutmarkoffset      \cutmarkoffset      \plusone
 
 \mutable\let\cutmarksymbol       \relax
-\mutable\let\cutmarktoptext      \empty
-\mutable\let\cutmarkbottomtext   \empty
-\mutable\let\cutmarkhoffset      \empty
-\mutable\let\cutmarkvoffset      \empty
 \mutable\def\cutmarklength       {2\bodyfontsize}
 \mutable\def\cutmarkrulethickness{\onepoint}
 
+\mutable\lettonothing\cutmarktoptext
+\mutable\lettonothing\cutmarkbottomtext
+\mutable\lettonothing\cutmarkhoffset
+\mutable\lettonothing\cutmarkvoffset
+
 \permanent\protected\def\horizontalcuts
   {\hpack to \d_pack_cutmarks_width
      {\dorecurse\horizontalcutmarks{\vrule\s!width\cutmarkrulethickness\s!height\cutmarklength\hfill}%
@@ -122,7 +123,7 @@
            {\scratchskip\ifempty\cutmarkhoffset\cutmarkoffset\scratchdimen\else\cutmarkhoffset\fi
             \setbox\scratchbox\hpack{\verticalcuts}%
             \llap{\copy\scratchbox\hskip\scratchskip}%
-            \ifdim\d_pack_cutmarks_depth=\zeropoint
+            \ifzeropt\d_pack_cutmarks_depth
               \hfill
             \else
               \bgroup
diff --git a/tex/context/base/mkxl/pack-lyr.mkxl b/tex/context/base/mkxl/pack-lyr.mkxl
index 3b7e2324d..e1652273e 100644
--- a/tex/context/base/mkxl/pack-lyr.mkxl
+++ b/tex/context/base/mkxl/pack-lyr.mkxl
@@ -97,35 +97,35 @@
 
 \permanent\def\layeranchor{\currentlayer:\the\realpageno}
 
-\let\p_pack_layers_doublesided\empty
-\let\p_pack_layers_state      \empty
-\let\p_pack_layers_option     \empty
-\let\p_pack_layers_method     \empty
-\let\p_pack_layers_preset     \empty
-\let\p_pack_layers_rotation   \empty
-\let\p_pack_layers_position   \empty
-\let\p_pack_layers_hoffset    \empty
-\let\p_pack_layers_voffset    \empty
-\let\p_pack_layers_offset     \empty
-\let\p_pack_layers_dx         \empty
-\let\p_pack_layers_dy         \empty
-\let\p_pack_layers_sx         \empty
-\let\p_pack_layers_sy         \empty
-\let\p_pack_layers_x          \empty
-\let\p_pack_layers_y          \empty
-\let\p_pack_layers_corner     \empty
-\let\p_pack_layers_location   \empty
-\let\p_pack_layers_line       \empty
-\let\p_pack_layers_column     \empty
-\let\p_pack_layers_width      \empty
-\let\p_pack_layers_height     \empty
-\let\p_pack_layers_direction  \empty
-\let\p_pack_layers_region     \empty
-
-\let\m_pack_layers_page       \empty
-\let\m_pack_layers_target     \empty
-\let\m_pack_layers_region     \empty
-\let\m_pack_layers_anchor     \empty
+\lettonothing\p_pack_layers_doublesided
+\lettonothing\p_pack_layers_state
+\lettonothing\p_pack_layers_option
+\lettonothing\p_pack_layers_method
+\lettonothing\p_pack_layers_preset
+\lettonothing\p_pack_layers_rotation
+\lettonothing\p_pack_layers_position
+\lettonothing\p_pack_layers_hoffset
+\lettonothing\p_pack_layers_voffset
+\lettonothing\p_pack_layers_offset
+\lettonothing\p_pack_layers_dx
+\lettonothing\p_pack_layers_dy
+\lettonothing\p_pack_layers_sx
+\lettonothing\p_pack_layers_sy
+\lettonothing\p_pack_layers_x
+\lettonothing\p_pack_layers_y
+\lettonothing\p_pack_layers_corner
+\lettonothing\p_pack_layers_location
+\lettonothing\p_pack_layers_line
+\lettonothing\p_pack_layers_column
+\lettonothing\p_pack_layers_width
+\lettonothing\p_pack_layers_height
+\lettonothing\p_pack_layers_direction
+\lettonothing\p_pack_layers_region
+
+\lettonothing\m_pack_layers_page
+\lettonothing\m_pack_layers_target
+\lettonothing\m_pack_layers_region
+\lettonothing\m_pack_layers_anchor
 
 \newconditional\c_pack_layers_repeated
 \newconditional\c_pack_layers_trace
@@ -196,8 +196,8 @@
 %D \setlayer [identifier] [optional parameters] {data}
 %D \stoptyping
 
-\mutable\let\currentlayerwidth \empty
-\mutable\let\currentlayerheight\empty
+\mutable\lettonothing\currentlayerwidth
+\mutable\lettonothing\currentlayerheight
 
 \permanent\tolerant\protected\def\setcurrentlayerdimensions[#1]#*[#2]% name left|right
   {\edef\currentlayerwidth {\thelayerwidth {#2#1}}%
@@ -218,7 +218,7 @@
      \edef\m_pack_layers_target{#2}%
      \pack_layers_set_indeed{#3}%
    \orelse\ifhastok={#2}%
-     \let\m_pack_layers_target\empty
+     \lettonothing\m_pack_layers_target
      \pack_layers_set_indeed{#2}%
    \else
      \edef\m_pack_layers_target{#2}%
@@ -400,9 +400,11 @@
           {\alignedbox[\p_pack_layers_location]\vpack{\box\nextbox}}%
       \fi
       \ifnum\p_pack_layers_line=\zerocount\else % no \ifcase, can be negative
+    % \ifzero\p_pack_layers_line\else % todo: test this
         \advance\d_pack_layers_y_position\dimexpr\p_pack_layers_line\lineheight+\topskip-\lineheight-\ht\nextbox\relax
       \fi
       \ifnum\p_pack_layers_column=\zerocount\else % no \ifcase, can be negative
+    % \ifzero\p_pack_layers_column\else % todo: test this
         \advance\d_pack_layers_x_position\layoutcolumnoffset\p_pack_layers_column\relax
       \fi
       \ifx\p_pack_layers_location\v!grid
@@ -449,6 +451,7 @@
 
 \def\pack_layers_set_bottom_positions
   {\ifnum\p_pack_layers_line=\zerocount\else % can be < 0
+% {\ifzero\p_pack_layers_line\else % todo: test this
      \edef\p_pack_layers_line{\the\numexpr-\p_pack_layers_line+\layoutlines+\plusone\relax}% use counter instead ?
    \fi
    \ifdim\d_pack_layers_y_size>\zeropoint
@@ -459,6 +462,7 @@
 
 \def\pack_layers_set_right_positions
   {\ifnum\p_pack_layers_column=\zerocount\else % can be < 0
+% {\ifzero\p_pack_layers_column\else % todo: test this
      \edef\p_pack_layers_column{\the\numexpr-\layerparameter\c!column+\layoutcolumns+\plusone\relax}% use counter instead ?
    \fi
    \ifdim\d_pack_layers_x_size>\zeropoint
diff --git a/tex/context/base/mkxl/pack-mat.mkxl b/tex/context/base/mkxl/pack-mat.mkxl
index 66be25a9d..e336c195e 100644
--- a/tex/context/base/mkxl/pack-mat.mkxl
+++ b/tex/context/base/mkxl/pack-mat.mkxl
@@ -18,6 +18,9 @@
 
 \unprotect
 
+% todo \v!mathframed
+% todo \v!mathstrikeout
+
 \newconditional \c_framed_math_framed
 
 \installtextracker
@@ -25,44 +28,199 @@
   {\settrue \c_framed_math_framed}
   {\setfalse\c_framed_math_framed}
 
-\tolerant\protected\def\mathframed[#1]#:#2%
+\integerdef\c_framed_math_last_left \zerocount
+\integerdef\c_framed_math_last_right\zerocount
+
+\installglobalmacrostack\c_framed_math_last_left
+\installglobalmacrostack\c_framed_math_last_right
+
+\installcorenamespace{mathframed}
+
+\defineframed[\??mathframed]
+
+\setupframed[\??mathframed][\c!location=\v!middle]
+
+\tolerant\permanent\protected\def\definemathframed[#1]#*[#2]#*[#3]%
+  {\ifarguments\or
+     \defineframed[#1][\??mathframed]%
+   \or
+     \defineframed[#1][\??mathframed][#2]%
+   \or
+     \defineframed[#1][#2][#3]%
+   \fi
+   \tolerant\frozen\protected\defcsname#1\endcsname{\math_framed{#1}}}
+
+\definemathframed[mathframed]
+
+% \def\math_framed#1#*[#2]#:#3%
+%   {\begingroup
+%    \ifconditional\c_framed_math_framed
+%      \defineboxanchor[temp]%
+%    \fi
+%    \setmathatomrule\mathbegincode\mathbincode\allmathstyles\mathbegincode\mathbincode % hm
+%    \normalexpanded
+%      {\setbox\scratchbox\hpack
+%         \ifconditional\c_framed_math_framed
+%           \s!source \namedboxanchor{temp}
+%         \fi
+%         \s!ymove \Umathaxis\Ustyle\mathstyle
+%         \bgroup
+%           \localframedwithsettings
+%             [#1][#2]%
+%             {\startimath
+%              \Ustyle\mathstyle
+%              #3%
+%              \stopimath
+%              \integerdef\c_framed_math_last_left \lastleftclass
+%              \integerdef\c_framed_math_last_right\lastrightclass
+%              \push_macro_c_framed_math_last_left
+%              \push_macro_c_framed_math_last_right
+%              }%
+%         \egroup}%
+%    \pop_macro_c_framed_math_last_left
+%    \pop_macro_c_framed_math_last_right
+%    \mathatom
+%      \s!class \mathexplicitcode
+%      \ifnum\c_framed_math_last_left <\zerocount\else\s!leftclass \c_framed_math_last_left \fi
+%      \ifnum\c_framed_math_last_right<\zerocount\else\s!rightclass\c_framed_math_last_right\fi
+%      \bgroup
+%        \ifconditional\c_framed_math_framed
+%          \setboxanchor[temp][\c!corner={\v!left ,\v!bottom},\c!location={\v!right,\v!height}]%
+%            \hpack{\smallinfofont\the\c_framed_math_last_left}%
+%          \setboxanchor[temp][\c!corner={\v!right,\v!bottom},\c!location={\v!left ,\v!height}]%
+%            \hpack{\smallinfofont\the\c_framed_math_last_right}%
+%        \fi
+%        \box\scratchbox
+%      \egroup
+%    \endgroup}
+
+\dimensiondef\d_math_framed_offset\zeropoint
+
+\def\math_framed#1#*[#2]#:#3%
   {\begingroup
    \ifconditional\c_framed_math_framed
      \defineboxanchor[temp]%
    \fi
    \setmathatomrule\mathbegincode\mathbincode\allmathstyles\mathbegincode\mathbincode % hm
-   \normalexpanded
-     {\setbox\scratchbox\hpack
-        \ifconditional\c_framed_math_framed
-          \s!source \namedboxanchor{temp}
-        \fi
-        \s!ymove \Umathaxis\Ustyle\mathstyle
-        \bgroup
-          \framed
-            [\c!location=\v!middle,#1]
-            {\startimath
-             \Ustyle\mathstyle
-             #2%
-             \stopimath}%
-        \egroup}%
-   \scratchcounterone\lastleftclass
-   \scratchcountertwo\lastrightclass
- % \writestatus{!!}{[\number\lastleftclass,\number\lastrightclass]}%
+   %
+   \scratchdimen\Umathaxis\Ustyle\mathstyle
+   %
+   \edef\currentframed{#1}%
+   \setbox\scratchbox\hbox{\localframedwithsettings[#1][#2]%
+     {\strut\global\dimensiondef\d_math_framed_offset\dimexpr
+         \framedoffset/2
+%          +2\d_framed_linewidth
+      \relax}}%
+   %
+   \setbox\scratchbox\hpack\bgroup
+     \startimath
+     \Ustyle\mathstyle
+     #3%
+     \stopimath
+     \normalexpanded{\aftergrouped{%
+       \integerdef\c_framed_math_last_left \the\lastleftclass
+       \integerdef\c_framed_math_last_right\the\lastrightclass
+     }}%
+   \egroup
+   %
+   \boxymove\scratchbox\dimexpr
+     \scratchdimen
+     -\d_math_framed_offset/2
+   \relax
+   %
+   \setbox\scratchbox\hpack
+     \localframedwithsettings
+       [#1][#2]%
+       {\box\scratchbox}%
+   %
+   \boxymove\scratchbox\scratchdimen
+   %
+   \ifconditional\c_framed_math_framed
+     \boxsource\scratchbox \namedboxanchor{temp}% test
+   \fi
+   %
    \mathatom
      \s!class \mathexplicitcode
-     \ifnum\scratchcounterone<\zerocount\else\s!leftclass \scratchcounterone\fi
-     \ifnum\scratchcountertwo<\zerocount\else\s!rightclass\scratchcountertwo\fi
+     \ifnum\c_framed_math_last_left <\zerocount\else\s!leftclass \c_framed_math_last_left \fi
+     \ifnum\c_framed_math_last_right<\zerocount\else\s!rightclass\c_framed_math_last_right\fi
      \bgroup
        \ifconditional\c_framed_math_framed
-         \setboxanchor[temp][\c!corner={\v!left,\v!bottom},\c!location={\v!right,\v!height}]
-           \hpack{\smallinfofont \the\scratchcounterone}%
-         \setboxanchor[temp][\c!corner={\v!right,\v!bottom},\c!location={\v!left,\v!height}]
-           \hpack{\smallinfofont \the\scratchcountertwo}%
+         \setboxanchor[temp][\c!corner={\v!left ,\v!bottom},\c!location={\v!right,\v!height}]%
+           \hpack{\smallinfofont\the\c_framed_math_last_left}%
+         \setboxanchor[temp][\c!corner={\v!right,\v!bottom},\c!location={\v!left ,\v!height}]%
+           \hpack{\smallinfofont\the\c_framed_math_last_right}%
        \fi
        \box\scratchbox
      \egroup
    \endgroup}
 
+\defineoverlay[mathstrikeout][\useMPgraphic{\framedparameter{mp}}]
+
+\definemathframed
+  [mathstrikeout]
+  [\c!offset=\v!overlay,
+   \c!mp=mathstrikeout,
+   \c!rulethickness=1.5\linewidth,
+   \c!background={\v!foreground,mathstrikeout},
+  %\c!color=darkgreen,
+   \c!textstyle=\txx,
+   \c!mathstyle=\s!script,
+   \c!frame=\v!off,
+   \c!arrow=\v!yes]
+
+\definemathframed
+  [mathcrossout]
+  [mathstrikeout]
+  [\c!mp=mathcrossout,
+   strike:location=bottom]
+
+\permanent\protected\def\mathstrikeoutlabel
+  {\iftok{\framedparameter{strike:math}}\emptytoks
+     \useframedstyleandcolor\c!textstyle\c!color
+     \framedparameter{strike:text}%
+   \else
+     \startimath
+       \dousecolorparameter{\framedparameter\c!color}%  mathcolor
+       \usemathstyleparameter\framedparameter\c!mathstyle
+       \framedparameter{strike:math}%
+     \stopimath
+   \fi}
+
+\startuseMPgraphic{mathstrikeout}
+    path arr ; arr := (llcorner OverlayBox -- urcorner OverlayBox) ;
+    if "\framedparameter{arrow}" = "yes" : drawarrow else : draw fi arr
+        withpen pencircle scaled OverlayLineWidth
+        withcolor OverlayColor
+    ;
+    label.top("\mathstrikeoutlabel", point 1 of arr)
+        withcolor OverlayColor
+    ;
+  % draw OverlayBox
+  %     dashed evenly
+  %     withpen pencircle scaled .5OverlayLineWidth
+  %     withcolor OverlayColor
+  % ;
+    setbounds currentpicture to OverlayBox ;
+\stopuseMPgraphic
+
+\startuseMPgraphic{mathcrossout}
+    draw (
+            (llcorner OverlayBox -- urcorner OverlayBox) &&
+            (ulcorner OverlayBox -- lrcorner OverlayBox)
+        )
+        withpen pencircle scaled OverlayLineWidth
+        withcolor OverlayColor
+    ;
+    if "\framedparameter{strike:location}" = "bottom" :
+        label.bot("\mathstrikeoutlabel", center bottomboundary currentpicture)
+    else :
+        label.top("\mathstrikeoutlabel", center topboundary currentpicture)
+    fi
+        withcolor OverlayColor
+    ;
+    setbounds currentpicture to OverlayBox ;
+\stopuseMPgraphic
+
 %D \starttyping
 %D \enabletrackers[framed.math]
 %D
diff --git a/tex/context/base/mkxl/pack-obj.mkxl b/tex/context/base/mkxl/pack-obj.mkxl
index 3dad2644a..e0cce8e08 100644
--- a/tex/context/base/mkxl/pack-obj.mkxl
+++ b/tex/context/base/mkxl/pack-obj.mkxl
@@ -184,7 +184,7 @@
 
 %D For the moment here:
 
-\mutable\let\lastpredefinedsymbol\empty % some day we can do more at the lua end
+\mutable\lettonothing\lastpredefinedsymbol % some day we can do more at the lua end
 
 \permanent\protected\def\predefinesymbol[#1]%
   {\begingroup
diff --git a/tex/context/base/mkxl/pack-pos.mkxl b/tex/context/base/mkxl/pack-pos.mkxl
index e2fd1c8f8..872d334a7 100644
--- a/tex/context/base/mkxl/pack-pos.mkxl
+++ b/tex/context/base/mkxl/pack-pos.mkxl
@@ -56,10 +56,10 @@
 \permanent\tolerant\protected\def\startpositioning[#1]#*[#2]%
   {\bgroup
    \ifparameters
-     \let\currentpositioning\empty
+     \lettonothing\currentpositioning
    \or
      \ifhastok={#1}%
-       \let\currentpositioning\empty
+       \lettonothing\currentpositioning
        \setupcurrentpositioning[#1]%
      \else
        \edef\currentpositioning{#1}%
diff --git a/tex/context/base/mkxl/pack-rul.mkxl b/tex/context/base/mkxl/pack-rul.mkxl
index 3f43b2abc..3c4d77062 100644
--- a/tex/context/base/mkxl/pack-rul.mkxl
+++ b/tex/context/base/mkxl/pack-rul.mkxl
@@ -210,30 +210,30 @@
 \newdimen\d_framed_target_dp
 \newdimen\d_framed_linewidth  \aliased\let\ruledlinewidth\d_framed_linewidth % needed at lua end
 
-\let\p_framed_frame           \empty % \framedparameter\c!frame
-\let\p_framed_backgroundoffset\empty
-\let\p_framed_foregroundstyle \empty
-\let\p_framed_autostrut       \empty
-\let\p_framed_location        \empty
-\let\p_framed_orientation     \empty
-\let\p_framed_anchoring       \empty
-\let\p_framed_synchronize     \empty
-\let\p_framed_autowidth       \empty
-\let\p_framed_franalyze       \empty
-\let\p_framed_backgroundcorner\empty
-\let\p_framed_backgroundradius\empty
-\let\p_framed_framecorner     \empty
-\let\p_framed_frameradius     \empty
-\let\p_framed_lines           \empty
-\let\p_framed_empty           \empty
-\let\p_framed_backgroundcolor \empty
-\let\p_framed_framecolor      \empty
-\let\p_framed_component       \empty
-\let\p_framed_background      \empty
-\let\p_framed_rulethickness   \empty
-\let\p_framed_foregroundcolor \empty
-\let\p_framed_setups          \empty
-\let\p_framed_synchronize     \empty
+\lettonothing\p_framed_frame            % \framedparameter\c!frame
+\lettonothing\p_framed_backgroundoffset
+\lettonothing\p_framed_foregroundstyle
+\lettonothing\p_framed_autostrut
+\lettonothing\p_framed_location
+\lettonothing\p_framed_orientation
+\lettonothing\p_framed_anchoring
+\lettonothing\p_framed_synchronize
+\lettonothing\p_framed_autowidth
+\lettonothing\p_framed_franalyze
+\lettonothing\p_framed_backgroundcorner
+\lettonothing\p_framed_backgroundradius
+\lettonothing\p_framed_framecorner
+\lettonothing\p_framed_frameradius
+\lettonothing\p_framed_lines
+\lettonothing\p_framed_empty
+\lettonothing\p_framed_backgroundcolor
+\lettonothing\p_framed_framecolor
+\lettonothing\p_framed_component
+\lettonothing\p_framed_background
+\lettonothing\p_framed_rulethickness
+\lettonothing\p_framed_foregroundcolor
+\lettonothing\p_framed_setups
+\lettonothing\p_framed_synchronize
 
 %D We don't have to stick to a \TEX\ drawn rule, but also can use rounded
 %D or even fancier shapes, as we will see later on.
@@ -420,7 +420,7 @@
 \newdimen\d_overlay_offset
 \newdimen\d_overlay_linewidth
 
-\let\m_overlay_region\empty
+\lettonothing\m_overlay_region
 
 % expandable ... in a future version the space will go (in mp one can use Overlay*)
 
@@ -511,7 +511,7 @@
 
 \newtoks\everybackgroundbox
 
-\let\m_framed_background\empty % we might need a public name
+\lettonothing\m_framed_background % we might need a public name
 
 \def\pack_framed_process_background
   {\ifcsname\??overlaybuiltin\m_framed_background\endcsname
@@ -1112,14 +1112,14 @@
 \permanent\protected\lettonothing\localendstrut
 \permanent\protected\lettonothing\localstrut
 
-\mutable\let\localoffset \empty
-\mutable\let\localwidth  \empty
-\mutable\let\localheight \empty
-\mutable\let\localformat \empty
+\mutable\lettonothing\localoffset
+\mutable\lettonothing\localwidth
+\mutable\lettonothing\localheight
+\mutable\lettonothing\localformat
 
-\mutable\let\framedwidth \empty
-\mutable\let\framedheight\empty
-\mutable\let\framedoffset\empty
+\mutable\lettonothing\framedwidth
+\mutable\lettonothing\framedheight
+\mutable\lettonothing\framedoffset
 
 % better a constant:
 
@@ -1241,10 +1241,10 @@
      \ifcstok{\framedparameter\c!adaptive}\v!yes
        \let\p_framed_adaptive\s!delay
      \else
-       \let\p_framed_adaptive\empty
+       \lettonothing\p_framed_adaptive
      \fi
    \else
-     \let\p_framed_adaptive\empty
+     \lettonothing\p_framed_adaptive
      \edef\p_framed_lines{\framedparameter\c!lines}%
      \ifempty\p_framed_lines
      \orelse\ifcase\p_framed_lines
diff --git a/tex/context/base/mkxl/page-app.mkxl b/tex/context/base/mkxl/page-app.mkxl
index 660dcb879..e8cc12aaa 100644
--- a/tex/context/base/mkxl/page-app.mkxl
+++ b/tex/context/base/mkxl/page-app.mkxl
@@ -96,10 +96,10 @@
      {\setbox\b_page_fitting\hpack\bgroup
         \scale[\c!scale=\fittingpageparameter\c!scale]{\box\b_page_fitting}%
       \egroup}%
-   \ifdim\ht\b_page_fitting=\zeropoint
+   \ifzeropt\ht\b_page_fitting
      \ht\b_page_fitting\onepoint
    \fi
-   \ifdim\wd\b_page_fitting=\zeropoint
+   \ifzeropt\wd\b_page_fitting
      \wd\b_page_fitting\onepoint
    \fi
    \d_page_fitting_width \wd\b_page_fitting
diff --git a/tex/context/base/mkxl/page-bck.mkxl b/tex/context/base/mkxl/page-bck.mkxl
index 5c9b96fd7..597ab419e 100644
--- a/tex/context/base/mkxl/page-bck.mkxl
+++ b/tex/context/base/mkxl/page-bck.mkxl
@@ -52,7 +52,7 @@
 %D We keep calculations and checks to a minimum and also try to minimize
 %D the amount of tracing due to expansion.
 
-\mutable\let\currentotrbackground\empty
+\mutable\lettonothing\currentotrbackground
 
 %D This is the only spot where we have a low level dependency on the way
 %D parent chains are defined but we want the speed.
diff --git a/tex/context/base/mkxl/page-box.mklx b/tex/context/base/mkxl/page-box.mklx
index a65989222..1cd668e95 100644
--- a/tex/context/base/mkxl/page-box.mklx
+++ b/tex/context/base/mkxl/page-box.mklx
@@ -80,18 +80,18 @@
 %    \boxyoffset#box\dimexpr\boxyoffset#box-\topoffset\relax}
 
 % \def\page_boxes_apply_offset % #box
-%   {\unless\ifzeropt\topoffset % we can't do an unless here
+%   {\unless\ifdim\topoffset=\zeropoint
 %      \expandafter\page_boxes_apply_offset_indeed
-%    \orunless\ifzeropt\backoffset
+%    \orunless\ifdim\backoffset=\zeropoint
 %      \expandafter\page_boxes_apply_offset_indeed
 %    \else
 %      \expandafter\gobbleoneargument
 %    \fi}
 
 \def\page_boxes_apply_offset % #box
-  {\unless\ifdim\topoffset=\zeropoint
+  {\unless\ifzeropt\topoffset
      \expandafter\page_boxes_apply_offset_indeed
-   \orunless\ifdim\backoffset=\zeropoint
+   \orunless\ifzeropt\backoffset
      \expandafter\page_boxes_apply_offset_indeed
    \else
      \expandafter\gobbleoneargument
diff --git a/tex/context/base/mkxl/page-brk.mkxl b/tex/context/base/mkxl/page-brk.mkxl
index f30d9cb2c..af558b591 100644
--- a/tex/context/base/mkxl/page-brk.mkxl
+++ b/tex/context/base/mkxl/page-brk.mkxl
@@ -45,8 +45,8 @@
 \newtoks\everybeforepagebreak
 \newtoks\everyafterpagebreak
 
-\let\page_breaks_current_option \empty
-\let\page_breaks_current_options\empty
+\lettonothing\page_breaks_current_option
+\lettonothing\page_breaks_current_options
 
 \installcorenamespace{pagebreakmethod}
 \installcorenamespace{pagebreaks}
@@ -288,8 +288,8 @@
 \newtoks\everyaftercolumnbreak
 \newtoks\everysynchronizecolumn
 
-\let\page_breaks_columns_current_option \empty
-\let\page_breaks_columns_current_options\empty
+\lettonothing\page_breaks_columns_current_option
+\lettonothing\page_breaks_columns_current_options
 
 \def\page_breaks_columns_handle#1%
   {\edef\page_breaks_columns_current_options{#1}%
diff --git a/tex/context/base/mkxl/page-cst.mkxl b/tex/context/base/mkxl/page-cst.mkxl
index 12ee0bd38..d2058ec46 100644
--- a/tex/context/base/mkxl/page-cst.mkxl
+++ b/tex/context/base/mkxl/page-cst.mkxl
@@ -128,10 +128,10 @@
   {\bgroup
    \enforced\let\startpagegrid\page_grd_start_dummy
    \ifarguments
-     \let\currentpagegrid\empty
+     \lettonothing\currentpagegrid
    \or
      \ifhastok={#1}%
-       \let\currentpagegrid\empty
+       \lettonothing\currentpagegrid
        \setupcurrentpagegrid[#1]%
      \else
        \def\currentpagegrid{#1}%
diff --git a/tex/context/base/mkxl/page-flt.mkxl b/tex/context/base/mkxl/page-flt.mkxl
index a360dc42f..32f04e6b3 100644
--- a/tex/context/base/mkxl/page-flt.mkxl
+++ b/tex/context/base/mkxl/page-flt.mkxl
@@ -182,10 +182,10 @@
 %
 % \placefloatwithsetups[somefigure]{}{\externalfigure[dummy][width=5cm,height=2cm]}
 
-\mutable\let\floatsetupcaption\empty
-\mutable\let\floatsetupcontent\empty
-\mutable\let\floatsetupwidth  \empty
-\mutable\let\floatsetupheight \empty
+\mutable\lettonothing\floatsetupcaption
+\mutable\lettonothing\floatsetupcontent
+\mutable\lettonothing\floatsetupwidth
+\mutable\lettonothing\floatsetupheight
 
 \aliased\let\placesetupfloat\gobbleoneoptional
 
diff --git a/tex/context/base/mkxl/page-imp.mkxl b/tex/context/base/mkxl/page-imp.mkxl
index 5846fb22a..c9244224d 100644
--- a/tex/context/base/mkxl/page-imp.mkxl
+++ b/tex/context/base/mkxl/page-imp.mkxl
@@ -61,7 +61,7 @@
 \newbox        \shipoutscratchbox
 \setnewconstant\shipoutfinalizemethod\plusone
 
-\mutable\let\pagestoshipout\empty % {1,3,6}
+\mutable\lettonothing\pagestoshipout % {1,3,6}
 
 \permanent\protected\def\shipoutrange#1#2%
   {\begingroup
@@ -706,7 +706,7 @@
         \wd\arrangedpageA\paperwidth
         \outputarrangedbox\arrangedpageA
         \egroup
-        \ifdim\ht\arrangedpageB=\zeropoint
+        \ifzeropt\ht\arrangedpageB
           \exitloop
         \fi}%
      \global\arrangedpageN\zerocount
@@ -1367,10 +1367,10 @@
 \installcorenamespace {pageshift}
 
 \permanent\protected\tolerant\def\definepageshift[#1]#*[#2]#*[#3]%
-  {\setvalue{\??pageshift#2:#1}{#3}}
+  {\defcsname\??pageshift#2:#1\endcsname{#3}}
 
-\let\page_boxes_h_shifts\empty
-\let\page_boxes_v_shifts\empty
+\lettonothing\page_boxes_h_shifts
+\lettonothing\page_boxes_v_shifts
 
 \newcount\c_page_boxes_h_shifts
 \newcount\c_page_boxes_v_shifts
diff --git a/tex/context/base/mkxl/page-inf.mkxl b/tex/context/base/mkxl/page-inf.mkxl
index 107591af3..4865d5990 100644
--- a/tex/context/base/mkxl/page-inf.mkxl
+++ b/tex/context/base/mkxl/page-inf.mkxl
@@ -22,8 +22,8 @@
 \newtoks\everyresetversion
 \newtoks\everysetupversion
 
-\mutable\let\currentversioninfo\empty
-\mutable\let\currentversiontext\empty
+\mutable\lettonothing\currentversioninfo
+\mutable\lettonothing\currentversiontext
 
 \let\page_info_add_to_box\gobbleoneargument
 
@@ -35,12 +35,12 @@
      \edef\currentversiontext{\dummyparameter\c!text}%
    \else
      \edef\currentversioninfo{#1}%
-     \let \currentversiontext\empty
+     \lettonothing\currentversiontext
    \fi
    \ifcsname\??layoutinfo\currentversioninfo\endcsname
      \let\page_info_add_to_box\page_info_add_to_box_indeed
    \else
-     \let\currentversioninfo\empty
+     \lettonothing\currentversioninfo
      \let\page_info_add_to_box\gobbleoneargument
    \fi
    \the\everysetupversion}
@@ -57,7 +57,7 @@
   {\begincsname\??layoutinfo#1\endcsname}
 
 \installversioninfo\v!final
-  {\let\currentversioninfo\empty
+  {\lettonothing\currentversioninfo
    \let\page_info_add_to_box\gobbleoneargument}
 
 \installversioninfo\v!concept
diff --git a/tex/context/base/mkxl/page-inj.mklx b/tex/context/base/mkxl/page-inj.mklx
index 8732e2628..02f853c55 100644
--- a/tex/context/base/mkxl/page-inj.mklx
+++ b/tex/context/base/mkxl/page-inj.mklx
@@ -70,13 +70,13 @@
    \fi}
 
 \def\page_injections_direct_settings_parameters#settings% #parameters%
-  {\let\currentpageinjection\empty
+  {\lettonothing\currentpageinjection
    \checkpageinjectionparent
    \setupcurrentpageinjection[#settings]%
    \page_injections_direct_indeed}
 
 \def\page_injections_direct_parameters% #parameters%
-  {\let\currentpageinjection\empty
+  {\lettonothing\currentpageinjection
    \checkpageinjectionparent
    \page_injections_direct_indeed}
 
diff --git a/tex/context/base/mkxl/page-lay.mkxl b/tex/context/base/mkxl/page-lay.mkxl
index 628e112b6..d030c3ff9 100644
--- a/tex/context/base/mkxl/page-lay.mkxl
+++ b/tex/context/base/mkxl/page-lay.mkxl
@@ -154,7 +154,7 @@
       \page_layouts_check_next
     \or % \setuplayout[name]
       \ifx\currentlayout\v!reset
-        \let\currentlayout\empty
+        \lettonothing\currentlayout
       \fi
       \letlayoutparameter\c!state\v!normal % global ? still needed ?
       \glet\currentlayout\currentlayout % global
@@ -162,7 +162,7 @@
       \page_layouts_check_next
     \or % \setuplayout (reverts to main layout)
       \letlayoutparameter\c!state\v!normal % global ? still needed ?
-      \glet\currentlayout\empty % global
+      \glettonothing\currentlayout % global
       \page_layouts_synchronize
       \page_layouts_check_next
     \fi
@@ -334,8 +334,8 @@
 \let\v_page_target_top_fill   \relax
 \let\v_page_target_bottom_fill\relax
 
-\let\papersize     \empty
-\let\printpapersize\empty
+\lettonothing\papersize
+\lettonothing\printpapersize
 
 \def\v_page_target_top      {\namedlayouttargetparameter\papersize\c!top   }
 \def\v_page_target_bottom   {\namedlayouttargetparameter\papersize\c!bottom}
@@ -430,7 +430,7 @@
    \fi}
 
 \protected\def\page_paper_setup_size_settings[#1]% sometimes used to set paper/print size
-  {\let\currentlayouttarget\empty
+  {\lettonothing\currentlayouttarget
    \edef\m_layouttarget_paper_saved{\page_paper_the_paper_size{\layouttargetparameter\c!page }}%
    \edef\m_layouttarget_print_saved{\page_paper_the_print_size{\layouttargetparameter\c!paper}}%
    \setupcurrentlayouttarget[#1]%
@@ -570,7 +570,7 @@
    \page_paper_set_restore\m_page_asked_paper\m_page_asked_print
    %
    % locate page target
-   \let\currentlayouttarget\empty
+   \lettonothing\currentlayouttarget
    \page_paper_reset_paper
    \processcommacommand[\m_page_asked_paper]\page_paper_identify_target
    \ifempty\currentlayouttarget
@@ -661,8 +661,8 @@
     \let\synchronizegridsnapping\relax
 \fi
 
-\let\p_page_layouts_width \empty
-\let\p_page_layouts_height\empty
+\lettonothing\p_page_layouts_width
+\lettonothing\p_page_layouts_height
 
 \def\page_layouts_synchronize
   {\setups[\layoutparameter\c!preset]\relax
@@ -879,8 +879,40 @@
    \glet\v_page_layouts_pre_check\relax
    \page_layouts_synchronize}
 
+% \def\page_layouts_check_default
+%   {\ifcsname\namedlayouthash\v_real_page_normal\c!state\endcsname
+%      \page_layouts_check_default_indeed\v_real_page_normal
+%    \orelse\ifcsname\namedlayouthash\v_real_page_reverse\c!state\endcsname
+%      \page_layouts_check_default_indeed\v_real_page_reverse
+%    \orelse\ifcsname\namedlayouthash\v_real_page_named\c!state\endcsname
+%      \page_layouts_check_default_indeed\v_real_page_named
+%    \orelse\ifcsname\namedlayouthash\v_real_page_current\c!state\endcsname
+%      \page_layouts_check_default_indeed\v_real_page_current
+%    \orelse\ifcsname\namedlayouthash\v_real_page_odd_or_even\c!state\endcsname
+%      \page_layouts_check_default_indeed\v_real_page_odd_or_even
+%    \orelse\ifrelax\v_page_layouts_pre_check
+%      % okay
+%    \else
+%      \page_layouts_check_revert
+%    \fi}
+
+% \showframe
+%
+% \setuplayout         [width=100mm,height=200mm]
+% \definelayout[shorta][height=80mm]
+% \definelayout[shortb][height=130mm]
+%
+% \starttext
+%     \definelayout[2][shorta] \definelayout[4][shortb]
+%     \definelayout[7][shorta] \definelayout[8][shortb] % we need to check before
+%     \dorecurse{20}{#1: \samplefile{knuth}\par}
+% \stoptext
+
 \def\page_layouts_check_default
-  {\ifcsname\namedlayouthash\v_real_page_normal\c!state\endcsname
+  {\ifrelax\v_page_layouts_pre_check\else
+     \page_layouts_check_revert
+   \fi
+   \ifcsname\namedlayouthash\v_real_page_normal\c!state\endcsname
      \page_layouts_check_default_indeed\v_real_page_normal
    \orelse\ifcsname\namedlayouthash\v_real_page_reverse\c!state\endcsname
      \page_layouts_check_default_indeed\v_real_page_reverse
@@ -890,10 +922,10 @@
      \page_layouts_check_default_indeed\v_real_page_current
    \orelse\ifcsname\namedlayouthash\v_real_page_odd_or_even\c!state\endcsname
      \page_layouts_check_default_indeed\v_real_page_odd_or_even
-   \orelse\ifrelax\v_page_layouts_pre_check
-     % okay
-   \else
-     \page_layouts_check_revert
+ % \orelse\ifrelax\v_page_layouts_pre_check
+ %   % okay
+ % \else
+ %   \page_layouts_check_revert
    \fi}
 
 \permanent\protected\def\installlayoutmethod#1#2%
diff --git a/tex/context/base/mkxl/page-lin.mklx b/tex/context/base/mkxl/page-lin.mklx
index 5a1dc2e60..7383ab4ca 100644
--- a/tex/context/base/mkxl/page-lin.mklx
+++ b/tex/context/base/mkxl/page-lin.mklx
@@ -96,7 +96,8 @@
 \def\page_lines_start_define
   {\setxvalue{\??linenumberinginstance\currentlinenumbering}%
      {\clf_registerlinenumbering
-        continue {\ifnum\c_page_lines_mode=\zerocount\v!yes\else\v!no\fi}%
+      % continue {\ifnum\c_page_lines_mode=\zerocount\v!yes\else\v!no\fi}%
+        continue {\ifzero\c_page_lines_mode\v!yes\else\v!no\fi}%
         start    \linenumberingparameter\c!start
         step     \linenumberingparameter\c!step
         method   {\linenumberingparameter\c!method}%
@@ -107,7 +108,8 @@
   {\clf_setuplinenumbering
      \csname\??linenumberinginstance\currentlinenumbering\endcsname
      {%
-        continue {\ifnum\c_page_lines_mode=\zerocount\v!yes\else\v!no\fi}%
+      % continue {\ifnum\c_page_lines_mode=\zerocount\v!yes\else\v!no\fi}%
+        continue {\ifzero\c_page_lines_mode\v!yes\else\v!no\fi}%
      }%
    \relax}
 
@@ -116,7 +118,8 @@
      \clf_setuplinenumbering
        \lastnamedcs
        {%
-            continue {\ifnum\c_page_lines_mode=\zerocount\v!yes\else\v!no\fi}%
+          % continue {\ifnum\c_page_lines_mode=\zerocount\v!yes\else\v!no\fi}%
+            continue {\ifzero\c_page_lines_mode\v!yes\else\v!no\fi}%
             start    \linenumberingparameter\c!start
             step     \linenumberingparameter\c!step
             method   {\linenumberingparameter\c!method}%
@@ -222,17 +225,17 @@
   {\edef\m_argument{#1}%
    \ifx\m_argument\v!continue
      \c_page_lines_mode\zerocount
-     \let\currentlinenumbering\empty
+     \lettonothing\currentlinenumbering
    \else
      \c_page_lines_mode\plusone
      \ifx\m_argument\v!empty
-       \let\currentlinenumbering\empty
+       \lettonothing\currentlinenumbering
      \orelse\ifhastok={#1}%
-       \let\currentlinenumbering\empty
+       \lettonothing\currentlinenumbering
        \setupcurrentlinenumbering[#1]%
      \else
        \doifelsenumber\m_argument
-         {\let\currentlinenumbering\empty
+         {\lettonothing\currentlinenumbering
           \letlinenumberingparameter\c!start\m_argument}
          {\let\currentlinenumbering\m_argument}%
      \fi
@@ -574,8 +577,8 @@
 
 \permanent\def\currentreferencelinenumber{\clf_filterreference{linenumber}}
 
-\let\m_page_lines_from\empty
-\let\m_page_lines_to  \empty
+\lettonothing\m_page_lines_from
+\lettonothing\m_page_lines_to
 
 \permanent\protected\def\doifelsesamelinereference#1#2#3%
   {\doifelsereferencefound{lr:b:#1}
diff --git a/tex/context/base/mkxl/page-mcl.mkxl b/tex/context/base/mkxl/page-mcl.mkxl
index e88371da1..416d22348 100644
--- a/tex/context/base/mkxl/page-mcl.mkxl
+++ b/tex/context/base/mkxl/page-mcl.mkxl
@@ -465,7 +465,7 @@
    %
    \reseteverypar % todo
    %
-   \ifdim\pagetotal=\zeropoint \else
+   \ifzeropt\pagetotal\else
      \verticalstrut
      \vskip-\struttotal
    \fi
diff --git a/tex/context/base/mkxl/page-mix.mkxl b/tex/context/base/mkxl/page-mix.mkxl
index 21e923864..0210d75b3 100644
--- a/tex/context/base/mkxl/page-mix.mkxl
+++ b/tex/context/base/mkxl/page-mix.mkxl
@@ -262,7 +262,7 @@
    \global\setbox\b_page_mix_preceding\vbox % pack ?
      {\forgetall
       \page_otr_command_flush_top_insertions
-      \ifdim\htdp\b_page_mix_preceding=\zeropoint \else
+      \ifzeropt\htdp\b_page_mix_preceding\else
         \writestatus\m!columns{preceding error}%
         \unvbox\b_page_mix_preceding
       \fi
@@ -401,7 +401,7 @@
 %D \stopmixedcolumns
 %D \stoptyping
 
-\mutable\let\currentmixedcolumnsmethod\empty
+\mutable\lettonothing\currentmixedcolumnsmethod
 
 \installmacrostack\currentmixedcolumns
 \installmacrostack\currentmixedcolumnsmethod
@@ -448,7 +448,7 @@
 
 \def\page_mix_start_columns_b[#1][#2]%
   {\ifhastok={#1}%
-     \let\currentmixedcolumns\empty
+     \lettonothing\currentmixedcolumns
      \page_mix_error_b
      \page_mix_start_columns_checked\page_mix_start_columns_b_yes\page_mix_start_columns_b_nop[#1]%
    \else
@@ -473,7 +473,7 @@
   {\writestatus\m!columns{best use an instance of mixed columns}}
 
 \def\page_mix_start_columns_c[#1][#2]%
-  {\let\currentmixedcolumns\empty
+  {\lettonothing\currentmixedcolumns
    \page_mix_start_columns_checked
      \page_mix_start_columns_c_yes
      \page_mix_start_columns_c_nop}
@@ -614,7 +614,7 @@
 
 % \defcsname\??mixedcolumnsbefore\s!otr\endcsname
 %   {\par
-%    \ifdim\pagetotal=\zeropoint \else
+%    \ifzeropt\pagetotal\else
 %      \verticalstrut     % probably no longer needed
 %      \vskip-\struttotal % probably no longer needed
 %    \fi}
@@ -625,7 +625,7 @@
 %   {\par
 %    \global\advance\c_page_mix_otr_nesting\plusone
 %    \ifcase\c_page_mix_otr_nesting\or
-%      \ifdim\pagetotal=\zeropoint \else
+%      \ifzeropt\pagetotal\else
 %        \obeydepth % we could handle this in pre material
 %      \fi
 %    \fi}
@@ -634,7 +634,7 @@
   {\par
    \global\advance\c_page_mix_otr_nesting\plusone
    \ifcase\c_page_mix_otr_nesting\or
-     \ifdim\pagetotal=\zeropoint \else
+     \ifzeropt\pagetotal\else
        % make sure that whitespace and blanks are done
        \strut
        \vskip-\lineheight
@@ -871,7 +871,7 @@
         \page_mix_construct_and_shipout\box\b_page_mix_collected\zerocount % three arguments
         \setbox\b_page_mix_collected\vpack{\clf_mixflushrest}% we could avoid this
         \clf_mixcleanup
-        \ifdim\ht\b_page_mix_collected=\zeropoint
+        \ifzeropt\ht\b_page_mix_collected
             \exitloop
         \fi
       \fi}%
diff --git a/tex/context/base/mkxl/page-one.mkxl b/tex/context/base/mkxl/page-one.mkxl
index c14173223..40d7d0af0 100644
--- a/tex/context/base/mkxl/page-one.mkxl
+++ b/tex/context/base/mkxl/page-one.mkxl
@@ -337,7 +337,7 @@
 \newskip       \s_page_one_between_top_insert
 
 \def\page_one_prepare_top_float
-  {\ifdim\d_page_floats_inserted_top=\zeropoint
+  {\ifzeropt\d_page_floats_inserted_top
      \settrue\c_page_one_top_of_insert
    \else
      \setfalse\c_page_one_top_of_insert
@@ -558,7 +558,7 @@
 
 \protected\def\page_one_command_flush_margin_blocks
   {\ifconditional\c_page_margin_blocks_present % \ifvoid\b_page_margin_blocks \else
-     \ifdim\pagetotal=\zeropoint
+     \ifzeropt\pagetotal
         \null % \fixedspace
      \fi
      \page_otr_command_next_page % \page
diff --git a/tex/context/base/mkxl/page-pcl.mkxl b/tex/context/base/mkxl/page-pcl.mkxl
index 02f98a543..f546a6119 100644
--- a/tex/context/base/mkxl/page-pcl.mkxl
+++ b/tex/context/base/mkxl/page-pcl.mkxl
@@ -788,7 +788,7 @@
   {\begingroup
    \begingroup
    \doifelseassignment{#1}%
-     {\let\currentpagecolumns\empty
+     {\lettonothing\currentpagecolumns
       \setuppagecolumns[#1]}%
      {\edef\currentpagecolumns{#1}}%
    \edef\p_page{\pagecolumnsparameter\c!page}%
diff --git a/tex/context/base/mkxl/page-pst.mkxl b/tex/context/base/mkxl/page-pst.mkxl
index 16f71e0dc..79e3be29d 100644
--- a/tex/context/base/mkxl/page-pst.mkxl
+++ b/tex/context/base/mkxl/page-pst.mkxl
@@ -52,7 +52,7 @@
 \newcount      \c_page_postponed_blocks_next_page % set at the lua end
 \newconditional\c_page_postponed_busy
 
-\mutable\let\currentpostponedpage\empty
+\mutable\lettonothing\currentpostponedpage
 
 \permanent\protected\defcsname\e!start\v!postponing\endcsname
   {\bgroup
diff --git a/tex/context/base/mkxl/page-sid.mkxl b/tex/context/base/mkxl/page-sid.mkxl
index ec53a23a4..614945a9d 100644
--- a/tex/context/base/mkxl/page-sid.mkxl
+++ b/tex/context/base/mkxl/page-sid.mkxl
@@ -172,7 +172,7 @@
        % cutspace
      \fi
    \fi
-   \ifdim\d_page_sides_shift=\zeropoint \relax
+   \ifzeropt\d_page_sides_shift
      \ifnum\c_page_sides_float_type=\plusfour
        \global\advance\d_page_sides_shift\d_page_sides_extrashift
        \global\d_page_sides_extrashift\zeropoint
@@ -442,6 +442,9 @@
   {\iftracesidefloats
      \enabletrackers[otr.forcestrutdepth]% \c_page_force_strut_depth_trace_mode\plusone
    \fi
+ % \unless\ifvmode
+ %   \writestatus{side floats}{confusion}
+ % \fi
    % flush what we have and check
    \forcestrutdepth
    % trigger pagebuilder, \pageboundary gives nicer tracing
@@ -449,10 +452,7 @@
      \penalty\zerocount % works too
    \else
     %\tracingpages\plusone \tracingonline\plustwo
-     \begingroup
-   % \pageboundarypenalty\plustenthousand % is now:
      \pageboundary\plustenthousand % becomes a penalty (after triggering the callback) (experimental!)
-     \endgroup
     %\tracingpages\zerocount
    \fi
    \page_otr_command_set_vsize} % new, no longer really needed
diff --git a/tex/context/base/mkxl/page-str.mkxl b/tex/context/base/mkxl/page-str.mkxl
index 067283ee0..e883d8859 100644
--- a/tex/context/base/mkxl/page-str.mkxl
+++ b/tex/context/base/mkxl/page-str.mkxl
@@ -31,7 +31,7 @@
 
 \unprotect
 
-\mutable\let\currentoutputstream\empty
+\mutable\lettonothing\currentoutputstream
 
 \newif   \ifinoutputstream        % will become a conditional or mode
 \newtoks \everyenableoutputstream
diff --git a/tex/context/base/mkxl/page-txt.mklx b/tex/context/base/mkxl/page-txt.mklx
index a66dc0829..f8daa0c47 100644
--- a/tex/context/base/mkxl/page-txt.mklx
+++ b/tex/context/base/mkxl/page-txt.mklx
@@ -90,8 +90,8 @@
     \fi
 \to \everysetuplayoutelement
 
-\mutable\let\currenttextstate \empty
-\mutable\let\previoustextstate\empty
+\mutable\lettonothing\currenttextstate
+\mutable\lettonothing\previoustextstate
 
 \def\page_layouts_reset_element_status#vertical%
   {\gdefcsname\??layouttextsreset#vertical\endcsname{\page_layouts_set_element_status_normal#vertical}}
@@ -175,7 +175,7 @@
 \permanent\protected\def\setupfootertexts{\setuptexts[\v!footer]}
 \permanent\protected\def\setupbottomtexts{\setuptexts[\v!bottom]}
 
-\mutable\let\currentlayoutelementstate\empty
+\mutable\lettonothing\currentlayoutelementstate
 
 \permanent\tolerant\protected\def\setuptexts[#vertical]#spacer[#horizontal]#spacer[#a]#spacer[#b]#spacer[#c]#spacer[#d]%
   {\ifarguments
@@ -221,7 +221,7 @@
 
 \setvalue{\??layouttextstrut\v!yes}{\setstrut\strut} % maybe more variants
 
-\let\m_page_layouts_element_content\empty
+\lettonothing\m_page_layouts_element_content
 
 \protected\def\page_layouts_process_element_single#content%
   {\edef\m_page_layouts_element_content{\detokenize{#content}}% so no \v!xxx
@@ -272,7 +272,7 @@
 
 \newcount\c_page_layouts_element_state_n
 
-\mutable\let\textlinestatus\empty
+\mutable\lettonothing\textlinestatus
 
 \def\page_layouts_set_element_status#vertical%
   {\c_page_layouts_element_state_n=0\namedlayoutelementparameter#vertical\c!n\relax
@@ -451,8 +451,8 @@
    \box\b_page_layouts_element
    \vkern-#height\relax}
 
-\let\page_layouts_place_extra_text_left \empty % historic
-\let\page_layouts_place_extra_text_right\empty % historic
+\lettonothing\page_layouts_place_extra_text_left  % historic
+\lettonothing\page_layouts_place_extra_text_right % historic
 
 \def\page_layouts_place_text_line_right
   {\hpack
@@ -780,8 +780,8 @@
      \let\page_layouts_place_extra_text_left \page_layouts_place_page_number_left
      \let\page_layouts_place_extra_text_right\page_layouts_place_page_number_right
    \else
-     \let\page_layouts_place_extra_text_left \empty
-     \let\page_layouts_place_extra_text_right\empty
+     \lettonothing\page_layouts_place_extra_text_left
+     \lettonothing\page_layouts_place_extra_text_right
    \fi}
 
 \def\page_layouts_identify_page_number_location
diff --git a/tex/context/base/mkxl/publ-ini.mkxl b/tex/context/base/mkxl/publ-ini.mkxl
index a9597d854..25b436f7b 100644
--- a/tex/context/base/mkxl/publ-ini.mkxl
+++ b/tex/context/base/mkxl/publ-ini.mkxl
@@ -112,8 +112,8 @@
 %D to split between cite and list here as it only complicates matters (timing) and is
 %D not clear either.
 
-\mutable\let\currentbtxspecification        \empty
-\mutable\let\currentbtxspecificationfallback\empty
+\mutable\lettonothing\currentbtxspecification
+\mutable\lettonothing\currentbtxspecificationfallback
 
 \installmacrostack\currentbtxspecification
 \installmacrostack\currentbtxspecificationfallback
@@ -139,7 +139,7 @@
    \edef\currentbtxspecification{#1}%
    \edef\currentbtxspecificationfallback{\namedbtxparameter\currentbtxspecification\c!default}%
    \ifx\currentbtxspecificationfallback\currentbtxspecification
-     \let\currentbtxspecificationfallback\empty
+     \lettonothing\currentbtxspecificationfallback
    \fi
    \clf_btxsetspecification{\currentbtxspecification}}
 
@@ -152,7 +152,7 @@
   {\edef\currentbtxspecification{#1}%
    \edef\currentbtxspecificationfallback{\namedbtxparameter\currentbtxspecification\c!default}%
    \ifx\currentbtxspecificationfallback\currentbtxspecification
-     \let\currentbtxspecificationfallback\empty
+     \lettonothing\currentbtxspecificationfallback
    \fi
   % has to be done explicitly: \loadbtxdefinitionfile[\currentbtxspecification]%
    \ifempty\currentbtxspecification
@@ -367,8 +367,8 @@
 
 % access
 
-\let\currentbtxtag    \empty
-\let\currentbtxdataset\v!default
+\lettonothing\currentbtxtag
+\let         \currentbtxdataset\v!default
 
 \permanent\protected\def\setbtxentry[#1]% or maybe btxsetentry
   {\edef\currentbtxtag{\clf_btxsetentry{\currentbtxdataset}{#1}}}
@@ -441,30 +441,31 @@
 
 %D Variables:
 
-\mutable\let\currentbtxbacklink     \empty    \permanent\protected\def\btxsetbacklink     {\def\currentbtxbacklink}
-\mutable\let\currentbtxcategory     \empty    \permanent\protected\def\btxsetcategory     {\def\currentbtxcategory}
-\mutable\let\currentbtxcombis       \empty    \permanent\protected\def\btxsetcombis       {\def\currentbtxcombis}
-\mutable\let\currentbtxdataset      \empty    \permanent\protected\def\btxsetdataset      {\def\currentbtxdataset}
-\mutable\let\currentbtxfirst        \empty    \permanent\protected\def\btxsetfirst        {\def\currentbtxfirst}
-\mutable\let\currentbtxsecond       \empty    \permanent\protected\def\btxsetsecond       {\def\currentbtxsecond}
-\mutable\let\currentbtxsuffix       \empty    \permanent\protected\def\btxsetsuffix       {\def\currentbtxsuffix}
-\mutable\let\currentbtxinternal     \empty    \permanent\protected\def\btxsetinternal     {\def\currentbtxinternal}
-\mutable\let\currentbtxlefttext     \empty    \permanent\protected\def\btxsetlefttext     {\def\currentbtxlefttext}
-\mutable\let\currentbtxrighttext    \empty    \permanent\protected\def\btxsetrighttext    {\def\currentbtxrighttext}
-\mutable\let\currentbtxbefore       \empty    \permanent\protected\def\btxsetbefore       {\def\currentbtxbefore}
-\mutable\let\currentbtxafter        \empty    \permanent\protected\def\btxsetafter        {\def\currentbtxafter}
-\mutable\let\currentbtxlanguage     \empty    \permanent\protected\def\btxsetlanguage     {\def\currentbtxlanguage}
-\mutable\let\currentbtxtag          \empty    \permanent\protected\def\btxsettag          {\def\currentbtxtag}
-\mutable\let\currentbtxnumber       \empty    \permanent\protected\def\btxsetnumber       {\def\currentbtxnumber}
-\mutable\let\currentbtxfirstinternal\empty    \permanent\protected\def\btxsetfirstinternal{\def\currentbtxfirstinternal}
-\mutable\let\currentbtxlastinternal \empty    \permanent\protected\def\btxsetlastinternal {\def\currentbtxlastinternal}
+\mutable\lettonothing\currentbtxbacklink      \permanent\protected\def\btxsetbacklink     {\def\currentbtxbacklink}
+\mutable\lettonothing\currentbtxcategory      \permanent\protected\def\btxsetcategory     {\def\currentbtxcategory}
+\mutable\lettonothing\currentbtxcombis        \permanent\protected\def\btxsetcombis       {\def\currentbtxcombis}
+\mutable\lettonothing\currentbtxdataset       \permanent\protected\def\btxsetdataset      {\def\currentbtxdataset}
+\mutable\lettonothing\currentbtxfirst         \permanent\protected\def\btxsetfirst        {\def\currentbtxfirst}
+\mutable\lettonothing\currentbtxsecond        \permanent\protected\def\btxsetsecond       {\def\currentbtxsecond}
+\mutable\lettonothing\currentbtxsuffix        \permanent\protected\def\btxsetsuffix       {\def\currentbtxsuffix}
+\mutable\lettonothing\currentbtxinternal      \permanent\protected\def\btxsetinternal     {\def\currentbtxinternal}
+\mutable\lettonothing\currentbtxlefttext      \permanent\protected\def\btxsetlefttext     {\def\currentbtxlefttext}
+\mutable\lettonothing\currentbtxrighttext     \permanent\protected\def\btxsetrighttext    {\def\currentbtxrighttext}
+\mutable\lettonothing\currentbtxbefore        \permanent\protected\def\btxsetbefore       {\def\currentbtxbefore}
+\mutable\lettonothing\currentbtxafter         \permanent\protected\def\btxsetafter        {\def\currentbtxafter}
+\mutable\lettonothing\currentbtxlanguage      \permanent\protected\def\btxsetlanguage     {\def\currentbtxlanguage}
+\mutable\lettonothing\currentbtxtag           \permanent\protected\def\btxsettag          {\def\currentbtxtag}
+\mutable\lettonothing\currentbtxnumber        \permanent\protected\def\btxsetnumber       {\def\currentbtxnumber}
+\mutable\lettonothing\currentbtxfirstinternal \permanent\protected\def\btxsetfirstinternal{\def\currentbtxfirstinternal}
+\mutable\lettonothing\currentbtxlastinternal  \permanent\protected\def\btxsetlastinternal {\def\currentbtxlastinternal}
 
 \mutable\let\currentbtxauthorvariant\v!normal \permanent\protected\def\btxsetauthorvariant{\def\currentbtxauthorvariant}
-\mutable\let\currentbtxfirstnames   \empty    \permanent\protected\def\btxsetfirstnames   {\let\currentbtxfirstnames\currentbtxfirstnames_indeed}
-\mutable\let\currentbtxinitials     \empty    \permanent\protected\def\btxsetinitials     {\let\currentbtxinitials  \currentbtxinitials_indeed  }
-\mutable\let\currentbtxjuniors      \empty    \permanent\protected\def\btxsetjuniors      {\let\currentbtxjuniors   \currentbtxjuniors_indeed   }
-\mutable\let\currentbtxsurnames     \empty    \permanent\protected\def\btxsetsurnames     {\let\currentbtxsurnames  \currentbtxsurnames_indeed  }
-\mutable\let\currentbtxvons         \empty    \permanent\protected\def\btxsetvons         {\let\currentbtxvons      \currentbtxvons_indeed      }
+
+\mutable\lettonothing\currentbtxfirstnames \permanent\protected\def\btxsetfirstnames   {\let\currentbtxfirstnames\currentbtxfirstnames_indeed}
+\mutable\lettonothing\currentbtxinitials   \permanent\protected\def\btxsetinitials     {\let\currentbtxinitials  \currentbtxinitials_indeed  }
+\mutable\lettonothing\currentbtxjuniors    \permanent\protected\def\btxsetjuniors      {\let\currentbtxjuniors   \currentbtxjuniors_indeed   }
+\mutable\lettonothing\currentbtxsurnames   \permanent\protected\def\btxsetsurnames     {\let\currentbtxsurnames  \currentbtxsurnames_indeed  }
+\mutable\lettonothing\currentbtxvons       \permanent\protected\def\btxsetvons         {\let\currentbtxvons      \currentbtxvons_indeed      }
 
 \newconstant\currentbtxoverflow       \permanent\protected\def\btxsetoverflow   #1{\currentbtxoverflow   #1\relax}
 \newconstant\currentbtxconcat         \permanent\protected\def\btxsetconcat     #1{\currentbtxconcat     #1\relax}
@@ -479,70 +480,70 @@
 \protected\def\currentbtxsurnames_indeed  {\clf_btxcurrentsurnames  \numexpr\currentbtxauthorindex\relax}
 \protected\def\currentbtxvons_indeed      {\clf_btxcurrentvons      \numexpr\currentbtxauthorindex\relax}
 
-\mutable\let\currentbtxfirstpage    \empty    \permanent\protected\def\btxsetfirstpage#1{\def\currentbtxfirstpage{\btx_page_number{#1}}}
-\mutable\let\currentbtxlastpage     \empty    \permanent\protected\def\btxsetlastpage #1{\def\currentbtxlastpage {\btx_page_number{#1}}}
-
-\mutable\let\currentbtxfield          \empty
-\mutable\let\currentbtxfielddoi       \empty
-\mutable\let\currentbtxfieldmonth     \empty
-\mutable\let\currentbtxfieldyear      \empty
-\mutable\let\currentbtxfieldurl       \empty
-\mutable\let\currentbtxcriterium      \empty
-\mutable\let\currentbtxlist           \empty
-\mutable\let\currentbtxlistentry      \empty
-\mutable\let\currentbtxlistindex      \empty
-\mutable\let\currentbtxreference      \empty
-\mutable\let\currentbtxrenderingtitle \empty
-\mutable\let\currentbtxcitetag        \empty
+\mutable\lettonothing\currentbtxfirstpage \permanent\protected\def\btxsetfirstpage#1{\def\currentbtxfirstpage{\btx_page_number{#1}}}
+\mutable\lettonothing\currentbtxlastpage  \permanent\protected\def\btxsetlastpage #1{\def\currentbtxlastpage {\btx_page_number{#1}}}
+
+\mutable\lettonothing\currentbtxfield
+\mutable\lettonothing\currentbtxfielddoi
+\mutable\lettonothing\currentbtxfieldmonth
+\mutable\lettonothing\currentbtxfieldyear
+\mutable\lettonothing\currentbtxfieldurl
+\mutable\lettonothing\currentbtxcriterium
+\mutable\lettonothing\currentbtxlist
+\mutable\lettonothing\currentbtxlistentry
+\mutable\lettonothing\currentbtxlistindex
+\mutable\lettonothing\currentbtxreference
+\mutable\lettonothing\currentbtxrenderingtitle
+\mutable\lettonothing\currentbtxcitetag
 
 \mutable\def\currentbtxauthorvariant{normal}
 
 \protected\def\btx_reset_list % not needed as we're grouped
-  {\let\currentbtxcombis   \empty
-   \let\currentbtxcategory \empty
-   \let\currentbtxinternal \empty
-   \let\currentbtxlefttext \empty
-   \let\currentbtxrighttext\empty
-   \let\currentbtxbefore   \empty
-   \let\currentbtxafter    \empty
-   \let\currentbtxbacklink \empty
-   \let\currentbtxlanguage \empty
-   \let\currentbtxsuffix   \empty
-  %\let\currentbtxdataset  \empty % will always be set
-  %\let\currentbtxtag      \empty % will always be set
-   \let\currentbtxnumber   \empty}
+  {\lettonothing\currentbtxcombis
+   \lettonothing\currentbtxcategory
+   \lettonothing\currentbtxinternal
+   \lettonothing\currentbtxlefttext
+   \lettonothing\currentbtxrighttext
+   \lettonothing\currentbtxbefore
+   \lettonothing\currentbtxafter
+   \lettonothing\currentbtxbacklink
+   \lettonothing\currentbtxlanguage
+   \lettonothing\currentbtxsuffix
+  %\lettonothing\currentbtxdataset % will always be set
+  %\lettonothing\currentbtxtag     % will always be set
+   \lettonothing\currentbtxnumber}
 
 \protected\def\btx_reset_cite % check for less .. not all resets needed when we're grouped (only subcites)
-  {\let        \currentbtxfirst      \empty
-   \let        \currentbtxsecond     \empty
-   \let        \currentbtxsuffix     \empty
-   \let        \currentbtxinternal   \empty
-   \let        \currentbtxlefttext   \empty
-   \let        \currentbtxrighttext  \empty
-   \let        \currentbtxbefore     \empty
-   \let        \currentbtxafter      \empty
-   \let        \currentbtxbacklink   \empty
-   \let        \currentbtxlanguage   \empty
-  %\let        \currentbtxdataset    \empty % will always be set, beware of local reset ~
-  %\let        \currentbtxtag        \empty % will always be set, beware of local reset ~
-   \let        \currentbtxnumber     \empty
-   \setconstant\currentbtxoverflow   \zerocount
-   \setconstant\currentbtxconcat     \zerocount
-   \setconstant\currentbtxcount      \zerocount}
+  {\lettonothing\currentbtxfirst
+   \lettonothing\currentbtxsecond
+   \lettonothing\currentbtxsuffix
+   \lettonothing\currentbtxinternal
+   \lettonothing\currentbtxlefttext
+   \lettonothing\currentbtxrighttext
+   \lettonothing\currentbtxbefore
+   \lettonothing\currentbtxafter
+   \lettonothing\currentbtxbacklink
+   \lettonothing\currentbtxlanguage
+  %\lettonothing\currentbtxdataset % will always be set, beware of local reset ~
+  %\lettonothing\currentbtxtag     % will always be set, beware of local reset ~
+   \lettonothing\currentbtxnumber
+   \setconstant\currentbtxoverflow\zerocount
+   \setconstant\currentbtxconcat\zerocount
+   \setconstant\currentbtxcount\zerocount}
 
 \protected\def\btx_reset_page % probably not needed
-  {\let        \currentbtxfirstpage    \empty
-   \let        \currentbtxlastpage     \empty
-   \let        \currentbtxfirstinternal\empty
-   \let        \currentbtxlastinternal \empty
-   \setconstant\currentbtxoverflow     \zerocount
-   \setconstant\currentbtxconcat       \zerocount
-   \setconstant\currentbtxcount        \zerocount}
+  {\lettonothing\currentbtxfirstpage
+   \lettonothing\currentbtxlastpage
+   \lettonothing\currentbtxfirstinternal
+   \lettonothing\currentbtxlastinternal
+   \setconstant\currentbtxoverflow\zerocount
+   \setconstant\currentbtxconcat\zerocount
+   \setconstant\currentbtxcount\zerocount}
 
 \protected\def\btx_reset_numbering  % probably not needed
-  {\let        \currentbtxfirst \empty
-   \let        \currentbtxsecond\empty
-   \let        \currentbtxsuffix\empty
+  {\lettonothing\currentbtxfirst
+   \lettonothing\currentbtxsecond
+   \lettonothing\currentbtxsuffix
    \setconstant\currentbtxconcat\zerocount}
 
 %D Pages:
@@ -775,9 +776,9 @@
     \fi
     %
     \iflocation
-        \letinteractionparameter\c!style\empty
-%         \letinteractionparameter\c!color\empty
-%         \letinteractionparameter\c!contrastcolor\empty
+        \resetinteractionparameter\c!style
+       %\resetinteractionparameter\c!color
+       %\resetinteractionparameter\c!contrastcolor
     \fi
 \to \everybtxlistrendering
 
@@ -968,7 +969,7 @@
 
 \newcount\c_btx_list_index
 
-\let\m_btx_list_action\empty
+\lettonothing\m_btx_list_action
 
 \def\publ_flush_list_step_command
   {\btxsetlisttag{\c_btx_list_index}
@@ -1170,8 +1171,8 @@
 
 \aliased\let\btxcitereference\btx_cite_reference_inject
 
-\mutable\let\currentbtxnumbering       \empty
-\mutable\let\currentbtxcitealternative \empty
+\mutable\lettonothing\currentbtxnumbering
+\mutable\lettonothing\currentbtxcitealternative
 
 \appendtoks
     \edef\currentbtxnumbering{\btxrenderingparameter\c!numbering}%
@@ -1181,7 +1182,7 @@
         \letlistparameter\c!headnumber\v!always
     \orelse\ifx\currentbtxnumbering\v!no
         \letlistparameter\c!headnumber\v!no
-        \let\currentbtxnumbering\empty
+        \lettonothing\currentbtxnumbering
       % \letlistparameter\c!textcommand\outdented % needed? we can use titlealign
         \letlistparameter\c!symbol     \v!none
         \letlistparameter\c!aligntitle \v!yes
@@ -1303,7 +1304,7 @@
 \newconditional\btxinteractivetext
 \newconditional\btxinteractivepage
 
-\mutable\let\currentbtxinteraction\empty
+\mutable\lettonothing\currentbtxinteraction
 
 \installcorenamespace{btxinteraction}
 
@@ -1323,7 +1324,7 @@
         \ifx\currentbtxinteraction\v!stop
             \setfalse\btxinteractive
         \else
-            \enforced\let\structurelistlocation\empty
+            \enforced\lettonothing\structurelistlocation
             \settrue\btxinteractive
             \begincsname\??btxinteraction\currentbtxinteraction\endcsname
         \fi
@@ -1376,13 +1377,13 @@
 % text   : not to list, show in text
 % always : mark for list, show in text
 
-\let\p_publ_cite_before   \empty
-\let\p_publ_cite_after    \empty
-\let\p_publ_cite_lefttext \empty
-\let\p_publ_cite_righttext\empty
+\lettonothing\p_publ_cite_before
+\lettonothing\p_publ_cite_after
+\lettonothing\p_publ_cite_lefttext
+\lettonothing\p_publ_cite_righttext
 
-\mutable\let\currentbtxciteuservariables\empty
-\mutable\let\currentbtxcitealternative  \empty
+\mutable\lettonothing\currentbtxciteuservariables
+\mutable\lettonothing\currentbtxcitealternative
 
 \permanent\protected\def\btxhybridcite % so one can alias the old
   {\dontleavehmode
@@ -1393,7 +1394,7 @@
   {\strictdoifelsenextoptional{\publ_cite_tags_options_indeed{#1}}{\publ_cite_tags_indeed{#1}}}
 
 \protected\def\publ_cite_tags_indeed#1%
-  {\letinteractionparameter\c!style\empty
+  {\resetinteractionparameter\c!style
    \setbtxparametersetroot\s!cite % we need to get the default
    \edef\currentbtxcitealternative{\btxparameter\c!alternative}%
    \setbtxparameterset\s!cite\currentbtxcitealternative
@@ -1406,14 +1407,14 @@
   {\doifelseassignment{#1}\publ_cite_tags_settings_indeed\publ_cite_tags_variants_indeed{#1}}
 
 \def\publ_cite_tags_settings_indeed#1[#2]%
-  {\letinteractionparameter\c!style\empty
-  %\letinteractionparameter\c!color\empty
-   \letdummyparameter\c!reference  \empty
-   \letdummyparameter\c!alternative\empty
-   \letdummyparameter\c!before     \empty
-   \letdummyparameter\c!after      \empty
-   \letdummyparameter\c!lefttext   \empty
-   \letdummyparameter\c!righttext  \empty
+  {\resetinteractionparameter\c!style
+  %\resetinteractionparameter\c!color
+   \resetdummyparameter\c!reference
+   \resetdummyparameter\c!alternative
+   \resetdummyparameter\c!before
+   \resetdummyparameter\c!after
+   \resetdummyparameter\c!lefttext
+   \resetdummyparameter\c!righttext
    \getdummyparameters[#1]%
    \edef\p_reference{\dummyparameter\c!reference}%
    \ifempty\p_reference
@@ -1447,7 +1448,7 @@
    \endgroup}
 
 \def\publ_cite_tags_variants_indeed#1[#2]%
-  {\letinteractionparameter\c!style\empty
+  {\resetinteractionparameter\c!style
    \edef\currentbtxcitealternative{#1}%
    \edef\currentbtxcitetag{#2}%
    \setbtxparameterset\s!cite\currentbtxcitealternative
@@ -1909,7 +1910,7 @@
 %     \btxusecommand[btx:apa:list:article:title]{foo}
 % \btxstopstyle
 
-\mutable\let\m_btx_saved_current\empty
+\mutable\lettonothing\m_btx_saved_current
 
 \permanent\protected\def\btxstartstyle[#1]%
   {\begingroup
diff --git a/tex/context/base/mkxl/regi-ini.mkxl b/tex/context/base/mkxl/regi-ini.mkxl
index 515b6afd6..8ba7edc42 100644
--- a/tex/context/base/mkxl/regi-ini.mkxl
+++ b/tex/context/base/mkxl/regi-ini.mkxl
@@ -23,7 +23,7 @@
 %D Beware, the enable and disable commands are global switches, so best use the
 %D start|/|stop commands.
 
-\mutable\let\currentregime\empty
+\mutable\lettonothing\currentregime
 
 \permanent\protected\def\enableregime[#1]{\clf_enableregime{#1}}
 \permanent\protected\def\disableregime   {\clf_disableregime}
diff --git a/tex/context/base/mkxl/scrn-bar.mklx b/tex/context/base/mkxl/scrn-bar.mklx
index 4cfcbde81..8d2f30d03 100644
--- a/tex/context/base/mkxl/scrn-bar.mklx
+++ b/tex/context/base/mkxl/scrn-bar.mklx
@@ -64,7 +64,7 @@
   {\iflocation
      \begingroup
      \ifhastok={#tag}%
-       \let\currentinteractionbar\empty
+       \lettonothing\currentinteractionbar
        \setupcurrentinteractionbar[#tag]%
        \edef\currentinteractionbar{\interactionbarparameter\c!alternative}%
      \else
@@ -112,7 +112,7 @@
 
 \def\scrn_bar_buttons_indeed#settings#list%
   {\begingroup
-  %\let\currentinteractionbar\empty
+  %\lettonothing\currentinteractionbar
    \setupcurrentinteractionbar[#settings]%
    \d_scrn_bar_width   \interactionbarparameter\c!width\relax
    \d_scrn_bar_distance\interactionbarparameter\c!distance\relax
@@ -121,7 +121,7 @@
    \fi
    \doifnothing{\interactionbarparameter\c!height}{\letinteractionbarparameter\c!height\v!broad}%
    \doifnothing{\interactionbarparameter\c!depth }{\letinteractionbarparameter\c!depth\zeropoint}%%%
-   \letinteractionbarparameter\c!background\empty
+   \resetinteractionbarparameter\c!background
    \setbox2\hbox{\inheritedinteractionbarframed{\symbol[\interactionparameter\c!symbolset][\v!previouspage]}}%
    \scratchheight\ht2 % needed because we default to nothing
    \letinteractionbarparameter\c!strut\v!no
diff --git a/tex/context/base/mkxl/scrn-but.mklx b/tex/context/base/mkxl/scrn-but.mklx
index 9832ffbbb..a3715c813 100644
--- a/tex/context/base/mkxl/scrn-but.mklx
+++ b/tex/context/base/mkxl/scrn-but.mklx
@@ -328,8 +328,8 @@
 
 \aliased\let\setupinteractionmenus\setupinteractionmenu
 
-\mutable\let\currentinteractionmenudistance\empty
-\mutable\let\currentinteractionmenustate   \empty
+\mutable\lettonothing\currentinteractionmenudistance
+\mutable\lettonothing\currentinteractionmenustate
 
 \let\scrn_menu_action\relax
 
@@ -434,7 +434,7 @@
 
 \newconditional\c_scrn_menu_zerodimensions
 
-\mutable\let\currentinteractionmenulocation\empty
+\mutable\lettonothing\currentinteractionmenulocation
 
 \def\scrn_menu_set_used
   {\d_scrn_menu_offset_left  \ifchkdim\interactionmenuparameter\c!leftoffset  \or\lastchkdim\else\zeropoint\fi
@@ -729,7 +729,7 @@
 \permanent\protected\def\scrn_menu_got_start[#action]#text\stopgot
   {\scrn_menu_action_start
    \letinteractionmenuparameter\c!frame\v!off
-   \letinteractionmenuparameter\c!background\empty
+   \resetinteractionmenuparameter\c!background
    \scrn_button_make
      \interactionmenuparameter
      \inheritedinteractionmenuframed
@@ -742,7 +742,7 @@
 \permanent\protected\def\scrn_menu_nop_start#text\stopnop
   {\scrn_menu_action_start
    \letinteractionmenuparameter\c!frame\v!off
-   \letinteractionmenuparameter\c!background\empty
+   \resetinteractionmenuparameter\c!background
    \letinteractionmenuparameter\c!empty\v!yes
    \inheritedinteractionmenuframed{\ignorespaces#text\removeunwantedspaces}%
    \scrn_menu_action_stop}
@@ -750,7 +750,7 @@
 \permanent\protected\def\scrn_menu_txt_start#text\stoptxt
   {\scrn_menu_action_start
    \letinteractionmenuparameter\c!frame\v!off
-   \letinteractionmenuparameter\c!background\empty
+   \resetinteractionmenuparameter\c!background
    \inheritedinteractionmenuframed{\ignorespaces#text\removeunwantedspaces}%
    \scrn_menu_action_stop}
 
@@ -1005,7 +1005,7 @@
 
 \def\scrn_menu_menu_button_b#settings#dummy#text#action%
   {\dontleavehmode \begingroup
-     \let\currentbutton\empty
+     \lettonothing\currentbutton
      \setupcurrentbutton[#settings]%
      \scrn_button_make
        \buttonparameter
diff --git a/tex/context/base/mkxl/scrn-fld.mklx b/tex/context/base/mkxl/scrn-fld.mklx
index 6c134268c..de448bf50 100644
--- a/tex/context/base/mkxl/scrn-fld.mklx
+++ b/tex/context/base/mkxl/scrn-fld.mklx
@@ -110,13 +110,13 @@
 \setupforms
   [\c!method=XML] % no need for everyjob initialization as this is the default
 
-\mutable\let\currentfieldbackgroundcolor     \empty
-\mutable\let\currentfieldbackgroundcolorvalue\empty
-\mutable\let\currentfieldbodycategory        \empty
-\mutable\let\currentfieldframecolor          \empty
-\mutable\let\currentfieldframecolorvalue     \empty
-\mutable\let\currentfieldlabel               \empty
-\mutable\let\currentfieldstackname           \empty
+\mutable\lettonothing\currentfieldbackgroundcolor
+\mutable\lettonothing\currentfieldbackgroundcolorvalue
+\mutable\lettonothing\currentfieldbodycategory
+\mutable\lettonothing\currentfieldframecolor
+\mutable\lettonothing\currentfieldframecolorvalue
+\mutable\lettonothing\currentfieldlabel
+\mutable\lettonothing\currentfieldstackname
 
 \appendtoks
     \iflocation
@@ -327,7 +327,7 @@
 %D (implemented as properties).
 
 \appendtoks
-    \let\currentfieldcategory\empty
+    \lettonothing\currentfieldcategory
     \doifelse{\interactionparameter\c!fieldlayer}\v!auto
       {\setupcurrentfieldcategory[\c!fieldlayer=\currentviewerlayer]}%
       {\setupcurrentfieldcategory[\c!fieldlayer=]}%
@@ -476,13 +476,13 @@
 \newconditional\fieldisvertical
 \newconditional\fieldishorizontal
 
-\mutable\let\currentfieldtotalframed  \empty
-\mutable\let\currentfieldlabelframed  \empty
-\mutable\let\currentfieldcontentframed\empty
+\mutable\lettonothing\currentfieldtotalframed
+\mutable\lettonothing\currentfieldlabelframed
+\mutable\lettonothing\currentfieldcontentframed
 
-\mutable\let\fieldtotalframedparameterhash  \empty % weird that we have to flag this
-\mutable\let\fieldlabelframedparameterhash  \empty % idem
-\mutable\let\fieldcontentframedparameterhash\empty % idem
+\mutable\lettonothing\fieldtotalframedparameterhash   % weird that we have to flag this
+\mutable\lettonothing\fieldlabelframedparameterhash   % idem
+\mutable\lettonothing\fieldcontentframedparameterhash % idem
 
 \permanent\tolerant\protected\def\field[#tag]#spacer[#label]% can be sped up with \setupcurrentfieldtotalframed etc
   {\iflocation
@@ -670,7 +670,7 @@
 \tolerant\def\scrn_tooltip_ignore[#settings]#:#anchortext#tiptext%
   {#anchortext}
 
-\mutable\let\currenttooltipname\empty
+\mutable\lettonothing\currenttooltipname
 
 \tolerant\def\scrn_tooltip_indeed[#settings]#:#anchortext#tiptext% a more modern aproach (push buttons)
   {\dontleavehmode \hbox \bgroup
@@ -683,7 +683,7 @@
        {\setupcurrenttooltip[#settings]}%
        {\setupcurrenttooltip[\c!location=#settings]}%
      \setbox\b_scrn_tooltip_text\hbox
-       {\lettooltipparameter\c!location\empty
+       {\resettooltipparameter\c!location
         \inheritedtooltipframed{#tiptext}}%
      \definesymbol
        [\currenttooltipname:txt]
@@ -986,7 +986,7 @@
        \setupcurrentinteractionmenu[#settings]%
        \let\scrn_rollbutton_symbol\scrn_rollbutton_symbol_m
      \orelse\ifhastok={#tag}%
-       \let\currentbutton\empty
+       \lettonothing\currentbutton
        \setupcurrentbutton[#tag]%
        \let\scrn_rollbutton_symbol\scrn_rollbutton_symbol_b
      \else
diff --git a/tex/context/base/mkxl/scrn-hlp.mklx b/tex/context/base/mkxl/scrn-hlp.mklx
index da2afd0d0..f8476cb8f 100644
--- a/tex/context/base/mkxl/scrn-hlp.mklx
+++ b/tex/context/base/mkxl/scrn-hlp.mklx
@@ -74,8 +74,8 @@
     \frozen\instance\protected\edefcsname\e!stop \currenthelp\endcsname{\scrn_help_stop                  }%
 \to \everydefinehelp
 
-\mutable\let\currenthelpreference\empty
-\mutable\let\currenthelpname     \empty
+\mutable\lettonothing\currenthelpreference
+\mutable\lettonothing\currenthelpname
 
 \protected\def\scrn_help_argument#category%
   {\def\currenthelp{#category}%
diff --git a/tex/context/base/mkxl/scrn-pag.mklx b/tex/context/base/mkxl/scrn-pag.mklx
index 09c542678..be1b6ad8f 100644
--- a/tex/context/base/mkxl/scrn-pag.mklx
+++ b/tex/context/base/mkxl/scrn-pag.mklx
@@ -35,9 +35,9 @@
 \newdimen\canvasbleedoffset
 \newdimen\canvasartoffset
 
-\mutable\let\currentinteractionscreendelay \empty
-\mutable\let\currentinteractionscreenheight\empty
-\mutable\let\currentinteractionscreenwidth \empty
+\mutable\lettonothing\currentinteractionscreendelay
+\mutable\lettonothing\currentinteractionscreenheight
+\mutable\lettonothing\currentinteractionscreenwidth
 
 \newconditional\c_scrn_canvas_tight_page
 
@@ -210,7 +210,7 @@
 }
 
 \appendtoks
-    \let\scrn_canvas_synchronize_common\empty
+    \lettonothing\scrn_canvas_synchronize_common
 \to \everyaftershipout
 
 \def\scrn_canvas_synchronize_only
@@ -289,12 +289,12 @@
 
 %D Page transitions:
 
-\let\scrn_transitions_list\empty
+\lettonothing\scrn_transitions_list
 
 \permanent\tolerant\protected\def\setuppagetransitions[#list]%
   {\edef\scrn_transitions_list{#list}%
    \ifx\scrn_transitions_list\v!reset
-     \let\scrn_transitions_list\empty
+     \lettonothing\scrn_transitions_list
    \fi}
 
 \def\scrn_transitions_set
diff --git a/tex/context/base/mkxl/scrn-ref.mklx b/tex/context/base/mkxl/scrn-ref.mklx
index ffe1fab16..b86677ab2 100644
--- a/tex/context/base/mkxl/scrn-ref.mklx
+++ b/tex/context/base/mkxl/scrn-ref.mklx
@@ -51,10 +51,10 @@
     \enabledirectives[destinations.offset=\the\dimexpr\interactionparameter\c!focusoffset\relax]%
 \to \everysetupinteraction
 
-\mutable\let\currentinteractioncloseaction    \empty
-\mutable\let\currentinteractionclosepageaction\empty
-\mutable\let\currentinteractionopenaction     \empty
-\mutable\let\currentinteractionopenpageaction \empty
+\mutable\lettonothing\currentinteractioncloseaction
+\mutable\lettonothing\currentinteractionclosepageaction
+\mutable\lettonothing\currentinteractionopenaction
+\mutable\lettonothing\currentinteractionopenpageaction
 
 %D We have to make sure of some settings:
 
diff --git a/tex/context/base/mkxl/scrn-wid.mklx b/tex/context/base/mkxl/scrn-wid.mklx
index 8bc3a3a1b..2361bbf3e 100644
--- a/tex/context/base/mkxl/scrn-wid.mklx
+++ b/tex/context/base/mkxl/scrn-wid.mklx
@@ -94,11 +94,11 @@
    \c!depth=\v!fit,
    \c!location=\v!high]
 
-\mutable\let\currentattachmentdepth     \empty
-\mutable\let\currentattachmentheight    \empty
-\mutable\let\currentattachmentregistered\empty
-\mutable\let\currentattachmentsymbol    \empty
-\mutable\let\currentattachmentwidth     \empty
+\mutable\lettonothing\currentattachmentdepth
+\mutable\lettonothing\currentattachmentheight
+\mutable\lettonothing\currentattachmentregistered
+\mutable\lettonothing\currentattachmentsymbol
+\mutable\lettonothing\currentattachmentwidth
 
 \permanent\tolerant\protected\def\registerattachment[#tag]#spacer[#settings]% we save (globally) at the lua end
   {\ifarguments\else
@@ -403,10 +403,10 @@
    \c!buffer=\v!comment,
    \c!location=\v!high]
 
-\mutable\let\currentcommentdepth \empty
-\mutable\let\currentcommentheight\empty
-\mutable\let\currentcommentsymbol\empty
-\mutable\let\currentcommentwidth \empty
+\mutable\lettonothing\currentcommentdepth
+\mutable\lettonothing\currentcommentheight
+\mutable\lettonothing\currentcommentsymbol
+\mutable\lettonothing\currentcommentwidth
 
 \appendtoks
     \frozen\protected\instance\edefcsname        \currentcomment\endcsname{\scrn_comment_argument[\currentcomment]}%
@@ -586,8 +586,8 @@
 %D \stoptext
 %D \stoptyping
 
-\mutable\let\currentrendering      \empty
-\mutable\let\currentrenderingwindow\empty
+\mutable\lettonothing\currentrendering
+\mutable\lettonothing\currentrenderingwindow
 
 \permanent\tolerant\protected\def\userendering[#tag]#spacer[#mime]#spacer[#file]#spacer[#option]%
   {\clf_registerrendering
@@ -617,11 +617,11 @@
 \installframedcommandhandler \??renderingwindow {renderingwindow} \??renderingwindow
 
 \appendtoks
-    \letrenderingwindowparameter\c!openpageaction \empty
-    \letrenderingwindowparameter\c!closepageaction\empty
-    \setrenderingwindowparameter\c!width          {\d_scrn_rendering_width }%
-    \setrenderingwindowparameter\c!height         {\d_scrn_rendering_height}%
-    \letrenderingwindowparameter\c!align          \v!flushleft
+    \resetrenderingwindowparameter\c!openpageaction
+    \resetrenderingwindowparameter\c!closepageaction
+    \setrenderingwindowparameter  \c!width          {\d_scrn_rendering_width }%
+    \setrenderingwindowparameter  \c!height         {\d_scrn_rendering_height}%
+    \letrenderingwindowparameter  \c!align          \v!flushleft
 \to \everypresetrenderingwindow
 
 \permanent\tolerant\protected\def\placerenderingwindow[#window]#spacer[#rendering]% do all in lua
diff --git a/tex/context/base/mkxl/spac-hor.mkxl b/tex/context/base/mkxl/spac-hor.mkxl
index 111bdc94c..ea43b2635 100644
--- a/tex/context/base/mkxl/spac-hor.mkxl
+++ b/tex/context/base/mkxl/spac-hor.mkxl
@@ -29,7 +29,7 @@
 \bitwiseflip \normalizeparmode \normalizeparnormalizeparcode
 \bitwiseflip \normalizeparmode \flattenvleadersnormalizeparcode
 
-\let\v_spac_indentation_current\empty % amount/keyword
+\lettonothing\v_spac_indentation_current % amount/keyword
 
 \newdimen \d_spac_indentation_par
 \parindent\d_spac_indentation_par % for the show
@@ -54,7 +54,7 @@
 
 \aliased\let\synchronizeindenting\spac_indentation_setup_size
 
-\let\m_spac_indentation_options\empty
+\lettonothing\m_spac_indentation_options
 
 \def\spac_indentation_setup_options[#1]%
   {\edef\m_spac_indentation_options{#1}% comma separated list
@@ -762,7 +762,7 @@
 
 \permanent\tolerant\protected\def\startnarrower[#1]%
   {\begingroup
-   \let\currentnarrower\empty
+   \lettonothing\currentnarrower
    \ifparameter#1\or
      \spac_narrower_start_apply{#1}%
    \else
@@ -870,12 +870,12 @@
 
 \installcorenamespace{tolerancemethods}
 
-\mutable\let\bottomtolerance\empty % why not zero (not used annyway, but for now we keep it)
+\mutable\lettonothing\bottomtolerance % why not zero (not used annyway, but for now we keep it)
 
 \permanent\protected\def\installtolerancemethod#1#2#3%
   {\defcsname\??tolerancemethods#1:#2\endcsname{#3}}
 
-\installtolerancemethod \v!vertical   \v!verystrict   {\let\bottomtolerance\empty} % why not zero
+\installtolerancemethod \v!vertical   \v!verystrict   {\lettonothing\bottomtolerance} % why not zero
 \installtolerancemethod \v!vertical   \v!strict       {\def\bottomtolerance{.050}}
 \installtolerancemethod \v!vertical   \v!tolerant     {\def\bottomtolerance{.075}}
 \installtolerancemethod \v!vertical   \v!verytolerant {\def\bottomtolerance{.100}}
diff --git a/tex/context/base/mkxl/spac-lin.mkxl b/tex/context/base/mkxl/spac-lin.mkxl
index 53da64923..f4473d2ea 100644
--- a/tex/context/base/mkxl/spac-lin.mkxl
+++ b/tex/context/base/mkxl/spac-lin.mkxl
@@ -63,7 +63,7 @@
    \frozen\instance\letvalue  {\e!stop \currentlines }\spac_lines_stop
 \to \everydefinelines
 
-\let\p_lines_option\empty
+\lettonothing\p_lines_option
 
 \let\spac_lines_break            \relax
 \let\spac_after_first_obeyed_line\relax
@@ -96,7 +96,7 @@
    \else
      \scratchdimen\dimexpr\commalistelement\relax
      \hskip
-       \ifdim\scratchdimen=\zeropoint
+       \ifzeropt\scratchdimen
          \zeropoint
        \else
          \scratchdimen
diff --git a/tex/context/base/mkxl/spac-pag.mkxl b/tex/context/base/mkxl/spac-pag.mkxl
index 32b3b8d79..ff85007b8 100644
--- a/tex/context/base/mkxl/spac-pag.mkxl
+++ b/tex/context/base/mkxl/spac-pag.mkxl
@@ -30,7 +30,7 @@
      \setpagestate[#1][\number#2]%
    \fi}
 
-\let\m_spac_pagestates_realpage\empty
+\lettonothing\m_spac_pagestates_realpage
 
 \newconditional\c_spac_pagestates_found
 
@@ -145,7 +145,7 @@
 
 \installcorenamespace{pagechanges}
 
-\newif\ifpagechanged \mutable\let\lastchangedpage\empty
+\newif\ifpagechanged \mutable\lettonothing\lastchangedpage
 
 \def\spac_pagechanges_check#1#2#3%
   {\pagechangedfalse
diff --git a/tex/context/base/mkxl/spac-par.mkxl b/tex/context/base/mkxl/spac-par.mkxl
index 098595dfe..654f195f6 100644
--- a/tex/context/base/mkxl/spac-par.mkxl
+++ b/tex/context/base/mkxl/spac-par.mkxl
@@ -227,7 +227,7 @@
 %D indentation as set (by the output routine) inside the group are forgotten
 %D afterwards. (I must not forget its existence).
 
-\mutable\let\currentparagraphproperties\empty % visible for tracing
+\mutable\lettonothing\currentparagraphproperties % visible for tracing
 
 \permanent\def\carryoverpar#1% #1 can be \endgroup or \egroup or ... expandable !
   {\normalexpanded
diff --git a/tex/context/base/mkxl/spac-ver.mkxl b/tex/context/base/mkxl/spac-ver.mkxl
index 755460ac2..bb12b5f5d 100644
--- a/tex/context/base/mkxl/spac-ver.mkxl
+++ b/tex/context/base/mkxl/spac-ver.mkxl
@@ -81,7 +81,7 @@
    \relax}
 
 \ifdefined\bodyfontinterlinespace \else
-  \let\bodyfontinterlinespace\empty
+  \lettonothing\bodyfontinterlinespace
 \fi
 
 \permanent\protected\def\presetnormallineheight % each bodyfont
@@ -118,12 +118,13 @@
 
 \installcorenamespace{interlinespacerelative}
 
-\aliased\let\setrelativeinterlinespace    \relax % used elsewhere
-\mutable\let\currentrelativeinterlinespace\empty
+\aliased\let\setrelativeinterlinespace\relax % used elsewhere
+
+\mutable\lettonothing\currentrelativeinterlinespace
 
 \defcsname\??interlinespacerelative\v!on   \endcsname{\oninterlineskip}
 \defcsname\??interlinespacerelative\v!off  \endcsname{\offinterlineskip}
-\defcsname\??interlinespacerelative\v!reset\endcsname{\enforced\let\currentrelativeinterlinespace\empty
+\defcsname\??interlinespacerelative\v!reset\endcsname{\enforced\lettonothing\currentrelativeinterlinespace
                                                       \enforced\let\setrelativeinterlinespace\relax
                                                       \setfontparameters}
 \defcsname\??interlinespacerelative\v!auto \endcsname{\enforced\let\setrelativeinterlinespace\spac_linespacing_set_relative_interlinespace}
@@ -501,7 +502,8 @@
   {\enforced\let\spac_lines_vbox\vbox}
 
 \let\v_spac_lines_around_action_set\relax
-\let\m_spac_lines_around           \empty
+
+\lettonothing\m_spac_lines_around
 
 \newconstant\c_spac_lines_correction_mode
 
@@ -1074,9 +1076,9 @@
 
 \appendtoks
  %  \setbox\strutbox\copy\nostrutbox
-    \enforced\let\strut   \empty
-    \enforced\let\endstrut\empty
-    \enforced\let\begstrut\empty
+    \enforced\lettonothing\strut
+    \enforced\lettonothing\endstrut
+    \enforced\lettonothing\begstrut
 \to \everysetnostrut
 
 %D When enabled, sigstruts will remove themselves if nothing goes inbetween. For
@@ -1429,7 +1431,7 @@
       \ifcsname\??gridsnappersets#1\endcsname\lastnamedcs\else#1\fi}}
 
 \permanent\protected\def\installsnapvalues#1#2%
-  {\let\m_spac_snapper\empty
+  {\lettonothing\m_spac_snapper
    \rawprocesscommacommand[#2]\spac_grids_expand_snapper
    \edef\p_spac_snapper{#1:\m_spac_snapper}%
    \ifcsname\??gridsnapperattributes\p_spac_snapper\endcsname
@@ -1649,14 +1651,15 @@
 \permanent\protected\def\setupgridsnapping[#1]% less overhead than setuplayout (needs testing)
   {\setlayoutparameter\c!grid{#1}\synchronizegridsnapping}
 
-\mutable\let\checkedgridmethod\empty   % these can become private
-\mutable\let\checkedgridscope \v!local % these can become private
+\mutable\lettonothing\checkedgridmethod % this can become private
+
+\mutable\let\checkedgridscope\v!local % this can become private
 
 \permanent\protected\def\checkgridmethod#1%
   {\edef\p_grid{#1}%
    \ifempty\p_grid
-     \let\checkedgridmethod\empty
-     \let\checkedgridscope \v!local
+     \lettonothing\checkedgridmethod
+     \let\checkedgridscope\v!local
    \else
      \splitatcolon\p_grid\checkedgridscope\checkedgridmethod
      \ifempty\checkedgridmethod
@@ -2179,12 +2182,12 @@
    \c!location=\v!left,
    \c!n=\zerocount]
 
-\let\m_spac_hanging_location\empty
+\lettonothing\m_spac_hanging_location
 
 \permanent\tolerant\protected\def\starthanging[#1]%
   {\dontleavehmode\bgroup
    \ifhastok={#1}%
-     \let\m_spac_hanging_location\empty
+     \lettonothing\m_spac_hanging_location
      \setupcurrenthanging[#1]%
    \else
      \edef\m_spac_hanging_location{#1}%
diff --git a/tex/context/base/mkxl/strc-bkm.mkxl b/tex/context/base/mkxl/strc-bkm.mkxl
index c5bd87324..8e5e7e4b1 100644
--- a/tex/context/base/mkxl/strc-bkm.mkxl
+++ b/tex/context/base/mkxl/strc-bkm.mkxl
@@ -90,8 +90,8 @@
      \expandafter\gobblethreeoptionals
    \fi}
 
-\let\m_bookmarks_names \empty
-\let\m_bookmarks_opened\empty
+\lettonothing\m_bookmarks_names
+\lettonothing\m_bookmarks_opened
 
 \tolerant\def\strc_bookmarks_place_yes[#1]#*[#2]#*[#3]%
   {\begingroup
@@ -104,7 +104,7 @@
      \let\m_bookmarks_names\v!all
    \fi
    \ifparameters\or\or
-     \doifelseassignment{#2}{\let\m_bookmarks_opened\empty\setupcurrentbookmark[#2]}\donothing
+     \doifelseassignment{#2}{\lettonothing\m_bookmarks_opened\setupcurrentbookmark[#2]}\donothing
    \or
      \setupcurrentbookmark[#3]% no every so not all possible
    \fi
diff --git a/tex/context/base/mkxl/strc-blk.mkxl b/tex/context/base/mkxl/strc-blk.mkxl
index 97ae671f1..c81739530 100644
--- a/tex/context/base/mkxl/strc-blk.mkxl
+++ b/tex/context/base/mkxl/strc-blk.mkxl
@@ -43,12 +43,12 @@
 
 % maybe: systemmode "block:<name>"
 
-\let\m_block   \empty
-\let\m_subblock\empty
+\lettonothing\m_block
+\lettonothing\m_subblock
 
 \protected\def\strc_blocks_begin#1%
-  {\edef\m_block   {#1}%
-   \let \m_subblock\empty
+  {\edef\m_block{#1}%
+   \lettonothing\m_subblock
    \doifelsenextoptionalcs\strc_blocks_begin_yes\strc_blocks_begin_nop}
 
 \protected\def\strc_blocks_begin_yes[#1]%
@@ -75,7 +75,7 @@
 
 % \tolerant\protected\def\strc_blocks_begin#1#*[#2]#*[#3]% #:#/% get rid of spaces and pars
 %   {\edef\m_block{#1}%
-%    \let\m_subblock\empty
+%    \lettonothing\m_subblock
 %    \ifhastok={#2}%
 %      \expandafter\strc_blocks_begin_a % [settings]
 %    \orelse\ifparameter#2\or
diff --git a/tex/context/base/mkxl/strc-con.mklx b/tex/context/base/mkxl/strc-con.mklx
index 55ddb8edf..d931bc779 100644
--- a/tex/context/base/mkxl/strc-con.mklx
+++ b/tex/context/base/mkxl/strc-con.mklx
@@ -105,28 +105,27 @@
 
 %aliased\let\currentconstructionhash           \??construction
 
-\mutable\let\currentconstructionmain           \empty
-\mutable\let\currentconstructionlevel          \empty
-\mutable\let\currentconstructionhandler        \empty
-
-\mutable\let\currentconstructionattribute      \empty
-\mutable\let\currentconstructionbookmark       \empty
-\mutable\let\currentconstructioncatcodes       \empty
-\mutable\let\currentconstructioncoding         \empty
-\mutable\let\currentconstructionexpansion      \empty
-\mutable\let\currentconstructionincrementnumber\empty
-\mutable\let\currentconstructionlabel          \empty
-\mutable\let\currentconstructionlist           \empty
-\mutable\let\currentconstructionlistentry      \empty
-\mutable\let\currentconstructionlistnumber     \empty
-\mutable\let\currentconstructionmarking        \empty
-\mutable\let\currentconstructionnumber         \empty
-\mutable\let\currentconstructionreference      \empty
-\mutable\let\currentconstructionreferencetext  \empty
-\mutable\let\currentconstructionreferenceprefix\empty
-\mutable\let\currentconstructionsynchronize    \empty
-\mutable\let\currentconstructiontitle          \empty
-\mutable\let\currentconstructionxmlsetup       \empty
+\mutable\lettonothing\currentconstructionmain
+\mutable\lettonothing\currentconstructionlevel
+\mutable\lettonothing\currentconstructionhandler
+\mutable\lettonothing\currentconstructionattribute
+\mutable\lettonothing\currentconstructionbookmark
+\mutable\lettonothing\currentconstructioncatcodes
+\mutable\lettonothing\currentconstructioncoding
+\mutable\lettonothing\currentconstructionexpansion
+\mutable\lettonothing\currentconstructionincrementnumber
+\mutable\lettonothing\currentconstructionlabel
+\mutable\lettonothing\currentconstructionlist
+\mutable\lettonothing\currentconstructionlistentry
+\mutable\lettonothing\currentconstructionlistnumber
+\mutable\lettonothing\currentconstructionmarking
+\mutable\lettonothing\currentconstructionnumber
+\mutable\lettonothing\currentconstructionreference
+\mutable\lettonothing\currentconstructionreferencetext
+\mutable\lettonothing\currentconstructionreferenceprefix
+\mutable\lettonothing\currentconstructionsynchronize
+\mutable\lettonothing\currentconstructiontitle
+\mutable\lettonothing\currentconstructionxmlsetup
 
 \settrue\c_strc_constructions_define_commands % use with care, might become a proper key
 
@@ -296,17 +295,17 @@
 \protected\defcsname\??constructioncommandhandler\v!construction\endcsname
   {\endgroup}
 
-\let\p_strc_constructions_sample        \empty
-\let\p_strc_constructions_align         \empty
-\let\p_strc_constructions_indenting     \empty
-\let\p_strc_constructions_width         \empty
-\let\p_strc_constructions_aligntitle    \empty
-\let\p_strc_constructions_renderingsetup\empty
-\let\p_strc_constructions_headalign     \empty
-\let\p_strc_constructions_hang          \empty
-\let\p_strc_constructions_inbetween     \empty
-\let\p_strc_constructions_closesymbol   \empty
-\let\p_strc_constructions_distance      \empty
+\lettonothing\p_strc_constructions_sample
+\lettonothing\p_strc_constructions_align
+\lettonothing\p_strc_constructions_indenting
+\lettonothing\p_strc_constructions_width
+\lettonothing\p_strc_constructions_aligntitle
+\lettonothing\p_strc_constructions_renderingsetup
+\lettonothing\p_strc_constructions_headalign
+\lettonothing\p_strc_constructions_hang
+\lettonothing\p_strc_constructions_inbetween
+\lettonothing\p_strc_constructions_closesymbol
+\lettonothing\p_strc_constructions_distance
 
 \newconditional\c_strc_constructions_distance_none
 
diff --git a/tex/context/base/mkxl/strc-des.mklx b/tex/context/base/mkxl/strc-des.mklx
index 9f9119466..6c04c9ac1 100644
--- a/tex/context/base/mkxl/strc-des.mklx
+++ b/tex/context/base/mkxl/strc-des.mklx
@@ -75,7 +75,7 @@
     \fi
 \to \everydefinedescription
 
-\let\p_strc_constructions_title \empty
+\lettonothing\p_strc_constructions_title
 
 \protected\defcsname\??constructioninitializer\v!description\endcsname
   {\let         \currentdescription              \currentconstruction
diff --git a/tex/context/base/mkxl/strc-doc.mkxl b/tex/context/base/mkxl/strc-doc.mkxl
index 50b71d9d2..11c96f9c1 100644
--- a/tex/context/base/mkxl/strc-doc.mkxl
+++ b/tex/context/base/mkxl/strc-doc.mkxl
@@ -19,45 +19,45 @@
 
 %D This will move:
 
-\mutable\let\currentstructureattribute               \empty
-\mutable\let\currentstructurebackreference           \empty
-\mutable\let\currentstructurebookmark                \empty
-\mutable\let\currentstructurecatcodes                \empty
-\mutable\let\currentstructurecoding                  \empty
-\mutable\let\currentstructurecoupling                \empty
-\mutable\let\currentstructureexpansion               \empty
-\mutable\let\currentstructureincrementnumber         \empty
-\mutable\let\currentstructurelabel                   \empty
-\mutable\let\currentstructurelevel                   \empty
-\mutable\let\currentstructurelist                    \empty
-\mutable\let\currentstructurelistattribute           \empty
-\mutable\let\currentstructuremarking                 \empty
-\mutable\let\currentstructurename                    \empty
-\mutable\let\currentstructureownnumber               \empty
-\mutable\let\currentstructureplaceholder             \empty
-\mutable\let\currentstructurereference               \empty
-\mutable\let\currentstructurereferenceattribute      \empty
-\mutable\let\currentstructurereferenceprefix         \empty
-\mutable\let\currentstructuresaveinlist              \empty
-\mutable\let\currentstructureshownumber              \empty
-\mutable\let\currentstructuretitle                   \empty
-\mutable\let\currentstructurexmlsetup                \empty
+\mutable\lettonothing\currentstructureattribute
+\mutable\lettonothing\currentstructurebackreference
+\mutable\lettonothing\currentstructurebookmark
+\mutable\lettonothing\currentstructurecatcodes
+\mutable\lettonothing\currentstructurecoding
+\mutable\lettonothing\currentstructurecoupling
+\mutable\lettonothing\currentstructureexpansion
+\mutable\lettonothing\currentstructureincrementnumber
+\mutable\lettonothing\currentstructurelabel
+\mutable\lettonothing\currentstructurelevel
+\mutable\lettonothing\currentstructurelist
+\mutable\lettonothing\currentstructurelistattribute
+\mutable\lettonothing\currentstructuremarking
+\mutable\lettonothing\currentstructurename
+\mutable\lettonothing\currentstructureownnumber
+\mutable\lettonothing\currentstructureplaceholder
+\mutable\lettonothing\currentstructurereference
+\mutable\lettonothing\currentstructurereferenceattribute
+\mutable\lettonothing\currentstructurereferenceprefix
+\mutable\lettonothing\currentstructuresaveinlist
+\mutable\lettonothing\currentstructureshownumber
+\mutable\lettonothing\currentstructuretitle
+\mutable\lettonothing\currentstructurexmlsetup
 
-\mutable\let\currentstructurecomponentattribute      \empty
-\mutable\let\currentstructurecomponentbookmark       \empty
-\mutable\let\currentstructurecomponentcatcodes       \empty
-\mutable\let\currentstructurecomponentcoding         \empty
-\mutable\let\currentstructurecomponentexpansion      \empty
-\mutable\let\currentstructurecomponentlabel          \empty
-\mutable\let\currentstructurecomponentlevel          \empty
-\mutable\let\currentstructurecomponentlist           \empty
-\mutable\let\currentstructurecomponentmarking        \empty
-\mutable\let\currentstructurecomponentname           \empty
-\mutable\let\currentstructurecomponentreference      \empty
-\mutable\let\currentstructurecomponentreferenceprefix\empty
-\mutable\let\currentstructurecomponentsynchronize    \empty
-\mutable\let\currentstructurecomponenttitle          \empty
-\mutable\let\currentstructurecomponentxmlsetup       \empty
+\mutable\lettonothing\currentstructurecomponentattribute
+\mutable\lettonothing\currentstructurecomponentbookmark
+\mutable\lettonothing\currentstructurecomponentcatcodes
+\mutable\lettonothing\currentstructurecomponentcoding
+\mutable\lettonothing\currentstructurecomponentexpansion
+\mutable\lettonothing\currentstructurecomponentlabel
+\mutable\lettonothing\currentstructurecomponentlevel
+\mutable\lettonothing\currentstructurecomponentlist
+\mutable\lettonothing\currentstructurecomponentmarking
+\mutable\lettonothing\currentstructurecomponentname
+\mutable\lettonothing\currentstructurecomponentreference
+\mutable\lettonothing\currentstructurecomponentreferenceprefix
+\mutable\lettonothing\currentstructurecomponentsynchronize
+\mutable\lettonothing\currentstructurecomponenttitle
+\mutable\lettonothing\currentstructurecomponentxmlsetup
 
 \permanent\protected\def\setstructuresynchronization#1% todo: use ctxcontext
   {\clf_setinternalreference
diff --git a/tex/context/base/mkxl/strc-enu.mklx b/tex/context/base/mkxl/strc-enu.mklx
index 89e1b307a..d3cf165de 100644
--- a/tex/context/base/mkxl/strc-enu.mklx
+++ b/tex/context/base/mkxl/strc-enu.mklx
@@ -146,10 +146,10 @@
      \frozen\protected\instance \defcsname\e!stop #tag\endcsname{\stopnamedenumeration}%
    \fi}
 
-\let\m_strc_enumeration_sub\empty
+\lettonothing\m_strc_enumeration_sub
 
 \appendtoks
-    \let\m_strc_enumeration_sub\empty
+    \lettonothing\m_strc_enumeration_sub
     \ifempty\currentenumerationparent
        % clone => parent | subclone => clone | subsubclone => subclone
        \strc_define_commands_enumeration
@@ -182,8 +182,8 @@
   %\strc_enumerations_setup_counter\currentenumeration
 \to \everydefineenumeration
 
-\let\p_strc_constructions_title \empty
-\let\p_strc_constructions_number\empty
+\lettonothing\p_strc_constructions_title
+\lettonothing\p_strc_constructions_number
 
 \protected\defcsname\??constructioninitializer\v!enumeration\endcsname
   {\let         \currentenumeration              \currentconstruction
diff --git a/tex/context/base/mkxl/strc-flt.mklx b/tex/context/base/mkxl/strc-flt.mklx
index 192fd137a..f444a9b1c 100644
--- a/tex/context/base/mkxl/strc-flt.mklx
+++ b/tex/context/base/mkxl/strc-flt.mklx
@@ -187,13 +187,13 @@
     \d_page_floats_compress_distance\floatparameter\c!compressdistance\relax
 \to \everysetupfloat
 
-\mutable\let\currentfloatattribute  \empty
-\mutable\let\currentfloatcounter    \empty
-\mutable\let\currentfloatgroup      \empty
-\mutable\let\currentfloatnumber     \empty
-\mutable\let\currentfloatsynchronize\empty
+\mutable\lettonothing\currentfloatattribute
+\mutable\lettonothing\currentfloatcounter
+\mutable\lettonothing\currentfloatgroup
+\mutable\lettonothing\currentfloatnumber
+\mutable\lettonothing\currentfloatsynchronize
 
-\let\m_strc_floats_previous_number  \empty % we can also just push/pop
+\lettonothing\m_strc_floats_previous_number % we can also just push/pop
 
 %D We need to do it again here:
 
@@ -323,12 +323,12 @@
 
 %D Captions.
 
-\mutable\let\floatcaptionarrangement\empty
-\mutable\let\floatcaptionattribute  \empty
-\mutable\let\floatcaptiondirectives \empty
-\mutable\let\floatcaptionlocation   \empty
-\mutable\let\floatcaptionnumber     \empty
-\mutable\let\floatcaptionsuffix     \empty
+\mutable\lettonothing\floatcaptionarrangement
+\mutable\lettonothing\floatcaptionattribute
+\mutable\lettonothing\floatcaptiondirectives
+\mutable\lettonothing\floatcaptionlocation
+\mutable\lettonothing\floatcaptionnumber
+\mutable\lettonothing\floatcaptionsuffix
 
 % For a while these were placeholders:
 %
@@ -419,7 +419,7 @@
 \newdimen\d_strc_floats_caption_height
 \newdimen\d_strc_floats_caption_depth
 
-\let\m_strc_floats_last_caption_tag\empty
+\lettonothing\m_strc_floats_last_caption_tag
 
 \def\strc_floats_make_complete_caption
   {\doifsomething{\floatcaptionparameter\c!spacebefore}{\blank[\floatcaptionparameter\c!spacebefore]}%
@@ -588,7 +588,7 @@
 % before we're really dealing with the float. Some day I'll root out the global
 % settings.
 
-\aliased\let\lastplacedfloat\empty
+\aliased\lettonothing\lastplacedfloat
 
 \def\strc_floats_set_current_tag#tag%
   {\edef\currentfloat{#tag}%
@@ -600,32 +600,33 @@
      {\writestatus\m!floatblocks{unknown float type '\currentfloat'}%
       \let\currentfloat\v!figure}% also a hack
    \enforced\glet\lastplacedfloat\currentfloat
-   \let\m_strc_floats_saved_userdata\empty
+   \lettonothing\m_strc_floats_saved_userdata
    \let\currentfloatcaption\currentfloat}
 
-\mutable\let\askedfloatmethod \empty
-\mutable\let\askedfloatoptions\empty
+\mutable\lettonothing\askedfloatmethod
+\mutable\lettonothing\askedfloatoptions
 
 \def\strc_floats_reset_variables
   {\global\emptyfloatcaptionfalse
    \global\nofloatcaptionfalse
    \global\nofloatnumberfalse
-   \glet\askedfloatmethod \empty
-   \glet\askedfloatoptions\empty}
+   \glettonothing\askedfloatmethod
+   \glettonothing\askedfloatoptions}
 
 % place
 
-\mutable\let\floatlabel         \empty
-\mutable\let\floatcolumn        \empty
-\mutable\let\floatrow           \empty
-\mutable\let\floatlocation      \empty
-\mutable\let\floatlocationmethod\empty
+\mutable\lettonothing\floatlabel
+\mutable\lettonothing\floatcolumn
+\mutable\lettonothing\floatrow
+\mutable\lettonothing\floatlocation
+\mutable\lettonothing\floatlocationmethod
+\mutable\lettonothing\floatlocationdefault
 
 \def\strc_floats_analyze_location
   {% more will be moved here
-   \let\floatlabel \empty
-   \let\floatcolumn\empty
-   \let\floatrow   \empty
+   \lettonothing\floatlabel
+   \lettonothing\floatcolumn
+   \lettonothing\floatrow
    %
    \edef\floatcaptionlocation{\floatcaptionparameter\c!location}%
    %
@@ -644,9 +645,10 @@
   {\strc_floats_set_current_tag{#tag}%
    \strc_floats_reset_variables
    \xdef\askedfloatoptions{#location}%
+   \edef\floatlocationdefault{\floatparameter\c!default}%
    \edef\floatlocation{#location}%
    \ifempty\floatlocation
-     \edef\floatlocation{\floatparameter\c!default}% beware of a clash between alignment locations
+     \let\floatlocation\floatlocationdefault % beware of a clash between alignment locations
    \fi
    \ifintable
      \the\c_floats_every_table_float
@@ -672,7 +674,7 @@
 
 \installsetuponlycommandhandler \??floatuserdata {floatuserdata}
 
-\let\m_strc_floats_saved_userdata\empty % todo: reset this in non start|stop cases
+\lettonothing\m_strc_floats_saved_userdata % todo: reset this in non start|stop cases
 
 %D We abuse the settings to pick up some float parameters too which makes it
 %D messy.
@@ -707,12 +709,13 @@
      \setupcurrentfloatuserdata[#userdata]%
      \def\m_strc_floats_saved_userdata{#userdata}%
    \else
-     \let\m_strc_floats_saved_userdata\empty
+     \lettonothing\m_strc_floats_saved_userdata
    \fi
-   % check
+   % check (see elsewhere
+   \edef\floatlocationdefault{\floatparameter\c!default}%
    \edef\floatlocation{\floatcaptionparameter\c!location}%
    \ifempty\floatlocation
-      \edef\floatlocation{\floatparameter\c!default}%
+     \let\floatlocation\floatlocationdefault % beware of a clash between alignment locations
    \fi
    % inherit
    \setexpandedfloatparameter\c!topoffset   {\floatcaptionparameter\c!topoffset}%
@@ -860,8 +863,9 @@
         \ifempty\forcedfloatmethod \else
           \doifelsecommandhandler\??float\forcedfloatmethod
             {\let\currentfloat\forcedfloatmethod
-             \edef\floatlocation{\floatparameter\c!default}%
-             \let\forcedfloatmethod\floatlocation}
+             \edef\floatlocationdefault{\floatparameter\c!default}%
+             \let\floatlocation\floatlocationdefault
+             \let\forcedfloatmethod\floatlocationdefault}
             \donothing
         \fi
         \ifempty\forcedfloatmethod
@@ -1114,14 +1118,14 @@
 %D \stopplacefigure
 %D \stoptyping
 
-\glet\currentsubfloatcounter\empty
+\glettonothing\currentsubfloatcounter
 
 \permanent\protected\def\startsubfloatnumbering
   {\glet\currentsubfloatcounter\s!unknown}
 
 \permanent\protected\def\stopsubfloatnumbering
   {\strc_counters_reset_sub\currentsubfloatcounter\plustwo
-   \glet\currentsubfloatcounter\empty}
+   \glettonothing\currentsubfloatcounter}
 
 \defineconversionset[subfloats][number,characters]
 
@@ -1135,8 +1139,8 @@
 \def\strc_floats_place_packaged_boxes_indeed#userdata%
   {\bgroup
    \ifconditional\usesamefloatnumber
-     \glet\currentfloatnumber     \m_strc_floats_previous_number
-     \glet\currentfloatattribute  \empty
+     \glet\currentfloatnumber\m_strc_floats_previous_number
+     \glettonothing\currentfloatattribute
      \glet\currentfloatsynchronize\relax
    \else
      \edef\currentfloatcounter{\namedcounterparameter\currentfloat\s!name}%
@@ -1327,7 +1331,7 @@
 \permanent\protected\def\hangsidefloat[#number]%
   {\global\c_page_sides_n_of_lines#number\relax}
 
-\mutable\let\extrafloatlocation\empty
+\mutable\lettonothing\extrafloatlocation
 
 \def\strc_floats_set_extra_action#rightpagelocation#leftpagelocation%
   {\rightorleftpageaction
@@ -1353,7 +1357,7 @@
 
 \def\strc_floats_check_extra_actions % less tracingthis way ....
   {\doifnotinset\v!text\floatlocation % fuzzy, text overloads left, since then it's a directive
-     {\let\extrafloatlocation\empty
+     {\lettonothing\extrafloatlocation
       % \d_page_sides_downshift will be reset afterwards, and can
       % already be set at this point
       \processcommacommand[\floatlocation]\strc_floats_check_extra_actions_step
@@ -2075,13 +2079,13 @@
 
 \def\strc_floats_build_box_top_stack_normal
   {\doifelseinset\v!overlay{\floatcaptionparameter\c!location}
-      \strc_floats_build_box_top_stack_normal_overlay
-      \strc_floats_build_box_top_stack_normal_content}
+     \strc_floats_build_box_top_stack_normal_overlay
+     \strc_floats_build_box_top_stack_normal_content}
 
 \def\strc_floats_build_box_bottom_stack_normal
   {\doifinset\v!overlay{\floatcaptionparameter\c!location}
-    \strc_floats_build_box_bottom_stack_normal_overlay
-    \strc_floats_build_box_bottom_stack_normal_content}
+     \strc_floats_build_box_bottom_stack_normal_overlay
+     \strc_floats_build_box_bottom_stack_normal_content}
 
 \def\strc_floats_build_box_top_stack_grid
   {\dp\b_strc_floats_caption\strutdepth
@@ -2504,13 +2508,12 @@
 
 \installcorenamespace{floatmethods}
 
-\mutable\let\floatmethod       \empty % set by lua
-\mutable\let\floatlabel        \empty % set by lua
-\mutable\let\floatcolumn       \empty % set by lua
-\mutable\let\floatrow          \empty % set by lua
-\mutable\let\floatspecification\empty
-
-\mutable\let\forcedfloatmethod \empty % set by lua and floatcombinations
+\mutable\lettonothing\floatmethod        % set by lua
+\mutable\lettonothing\floatlabel         % set by lua
+\mutable\lettonothing\floatcolumn        % set by lua
+\mutable\lettonothing\floatrow           % set by lua
+\mutable\lettonothing\floatspecification
+\mutable\lettonothing\forcedfloatmethod  % set by lua and floatcombinations
 
 \permanent\protected\def\setfloatmethodvariables#1% \floatmethod \floatlabel \floatrow \floatcolumn
   {\clf_analysefloatmethod{#1}} % move definition to lua end
@@ -2521,7 +2524,10 @@
 \def\strc_floats_get_box
   {\ifvisible
      \ifcsname\??floatmethods\currentoutputroutine:\floatmethod\endcsname \else
-        \let\floatmethod\v!here
+       \let\floatmethod\floatlocationdefault
+       \ifcsname\??floatmethods\currentoutputroutine:\floatmethod\endcsname \else
+         \let\floatmethod\v!here
+       \fi
      \fi
      \ifempty\forcedfloatmethod \else
        \let\floatmethod\forcedfloatmethod
@@ -2539,7 +2545,7 @@
 \installcorenamespace{floatsettings}
 
 \permanent\protected\def\installfloatmethod#1#2#3% routine keyword handler
-  {\setvalue{\??floatmethods#1:#2}{#3}}
+  {\defcsname\??floatmethods#1:#2\endcsname{#3}}
 
 \permanent\protected\def\handlefloatmethod#1%
   {\csname\??floatmethods\currentoutputroutine:#1\endcsname}
diff --git a/tex/context/base/mkxl/strc-itm.mklx b/tex/context/base/mkxl/strc-itm.mklx
index db6bdadf3..a4a0b283a 100644
--- a/tex/context/base/mkxl/strc-itm.mklx
+++ b/tex/context/base/mkxl/strc-itm.mklx
@@ -224,10 +224,10 @@
 \newcount      \c_strc_itemgroups_column_depth
 
 \def           \v_strc_itemgroups_counter        {itemgroup:\currentparentitemgroup}
-\let           \m_strc_itemgroups_repeat_start   \empty
+\lettonothing  \m_strc_itemgroups_repeat_start
 \def           \v_strc_itemgroups_unknown_symbol {?}
-\let           \m_strc_itemgroups_indenting      \empty
-\let           \m_strc_itemgroups_destination    \empty
+\lettonothing  \m_strc_itemgroups_indenting
+\lettonothing  \m_strc_itemgroups_destination
 
 \mutable\let   \currentitemlevel                 \!!zerocount % public
 \mutable\def   \currentnofitems                  {\the\c_strc_itemgroups_max_items}
@@ -235,9 +235,9 @@
 
 \newtoks       \itemgroupcommands                % maybe public
 
-\mutable\def   \currentitemgroupsymbol           {n}    % here we cannot use a _ in the name
-\mutable\let   \currentitemgroupconversionset    \empty % here we cannot use a _ in the name
-\mutable\let   \currentitemgroupsegments         \empty
+\mutable\def          \currentitemgroupsymbol        {n} % here we cannot use a _ in the name
+\mutable\lettonothing \currentitemgroupconversionset     % here we cannot use a _ in the name
+\mutable\lettonothing \currentitemgroupsegments
 
 \def\strc_itemgroups_register_status
   {\clf_registeritemgroup{\currentparentitemgroup}\c_strc_itemgroups_nesting\c_strc_itemgroups_n_of_items\dimexpr\itemgroupparameter\c!maxwidth\relax}
@@ -393,8 +393,8 @@
 % \protected\def\strc_itemgroups_process_options#options%
 %   {\normalexpanded{\strc_itemgroups_process_option_list[#options]}} % expansion of options is handy for xml
 
-\mutable\let\itemgroupfirst \empty
-\mutable\let\itemgroupsecond\empty
+\mutable\lettonothing\itemgroupfirst
+\mutable\lettonothing\itemgroupsecond
 
 \def\strc_itemgroups_process_option#option%
   {\edef\scratchstringone{#option}%
@@ -474,8 +474,8 @@
                                             %\letitemgroupparameter\c!factor       \!!zerocount
                                              \letitemgroupparameter\c!factor       {\zerocount}%
                                              \setitemgroupparameter\c!packcriterium{\zerocount}%
-                                             \letitemgroupparameter\c!inner        \empty
-                                             \letitemgroupparameter\c!beforehead   \empty
+                                             \resetitemgroupparameter\c!inner
+                                             \resetitemgroupparameter\c!beforehead
                                              \letitemgroupparameter\c!afterhead    \blank
                                              \letitemgroupparameter\c!before       \blank
                                              \letitemgroupparameter\c!inbetween    \blank
@@ -503,23 +503,30 @@
    \setfalse\c_strc_itemgroups_symbol
    \setfalse\c_strc_itemgroups_columns
    % to be checked
-   \let\m_strc_itemgroups_destination\empty
-   \let\strc_itemgroups_used_symbol  \empty % ** start value
-   \let\strc_itemgroups_margin_symbol\empty
-   \let\strc_itemgroups_extra_symbol \empty
+   \lettonothing\m_strc_itemgroups_destination
+   \lettonothing\strc_itemgroups_used_symbol   % ** start value
+   \lettonothing\strc_itemgroups_margin_symbol
+   \lettonothing\strc_itemgroups_extra_symbol
    %
    \global\letitemgroupparameter\c!maxwidth\!!zeropoint
    }
 
-\setvalue{\??itemgroupfirst\v!intro       }{\settrue\c_strc_itemgroups_intro}
-\setvalue{\??itemgroupfirst\v!continue    }{\settrue\c_strc_itemgroups_continue}
-\setvalue{\??itemgroupfirst\v!random      }{\settrue\c_strc_itemgroups_randomize
-                                            \settrue\c_strc_itemgroups_collecting}
-\setvalue{\??itemgroupkeyword\v!horizontal}{\settrue\c_strc_itemgroups_horizontal
-                                            \settrue\c_strc_itemgroups_collecting
-                                            \settrue\c_strc_itemgroups_inline
-                                            \settrue\c_strc_itemgroups_joined
-                                            \strc_itemgroups_process_set_option_pack}
+\defcsname\??itemgroupfirst\v!intro\endcsname
+  {\settrue\c_strc_itemgroups_intro}
+
+\defcsname\??itemgroupfirst\v!continue\endcsname
+  {\settrue\c_strc_itemgroups_continue}
+
+\defcsname\??itemgroupfirst\v!random\endcsname
+  {\settrue\c_strc_itemgroups_randomize
+   \settrue\c_strc_itemgroups_collecting}
+
+\defcsname\??itemgroupkeyword\v!horizontal\endcsname
+  {\settrue\c_strc_itemgroups_horizontal
+   \settrue\c_strc_itemgroups_collecting
+   \settrue\c_strc_itemgroups_inline
+   \settrue\c_strc_itemgroups_joined
+   \strc_itemgroups_process_set_option_pack}
 
 \def\strc_itemgroups_preset_stage_one#options%
   {\processcommacommand[#options]\strc_itemgroups_preset_stage_one_indeed}
@@ -741,11 +748,11 @@
 %    \strc_itemgroups_insert_reference
 %    \endgroup}
 
-\let\strc_itemgroups_temp_symbol  \empty
-\let\strc_itemgroups_used_symbol  \empty
-\let\strc_itemgroups_asked_symbol \empty
-\let\strc_itemgroups_margin_symbol\empty
-\let\strc_itemgroups_extra_symbol \empty
+\lettonothing\strc_itemgroups_temp_symbol
+\lettonothing\strc_itemgroups_used_symbol
+\lettonothing\strc_itemgroups_asked_symbol
+\lettonothing\strc_itemgroups_margin_symbol
+\lettonothing\strc_itemgroups_extra_symbol
 
 \def\strc_itemgroups_set_symbol#symbol%
   {\edef\strc_itemgroups_temp_symbol{#symbol}%
@@ -762,14 +769,14 @@
    \strc_itemgroups_store_global_symbol\currentitemgroupsymbol
    \strc_itemgroups_store_local_symbol\v_strc_itemgroups_unknown_symbol
    \let\strc_itemgroups_used_symbol\strc_itemgroups_set_symbol_symbol_item
-   \let\strc_itemgroups_asked_symbol\empty}
+   \lettonothing\strc_itemgroups_asked_symbol}
 
 \def\strc_itemgroups_set_symbol_conversion
   {\let\currentitemgroupsymbol\strc_itemgroups_temp_symbol
    \strc_itemgroups_store_global_symbol\currentitemgroupsymbol
    \strc_itemgroups_store_local_symbol\strc_itemgroups_insert_item_counter
    \let\strc_itemgroups_used_symbol\strc_itemgroups_set_symbol_conversion_item
-   \let\strc_itemgroups_asked_symbol\empty}
+   \lettonothing\strc_itemgroups_asked_symbol}
 
 \def\strc_itemgroups_set_symbol_symbol_item
   {\symbol[\currentitemgroupsymbol]}
@@ -802,8 +809,8 @@
    \advance\d_strc_itemgroups_list_width\itemgroupparameter\c!distance\relax
    \let\currentitemgroup\m_strc_itemgroups_saved}
 
-\let\p_itemgroups_options      \empty
-\let\p_itemgroups_extra_options\empty
+\lettonothing\p_itemgroups_options
+\lettonothing\p_itemgroups_extra_options
 
 \permanent\tolerant\protected\def\startitemgroup[#category]#spacer[#options]#spacer[#settings]%
   {\begingroup % (1)
@@ -816,7 +823,7 @@
    \edef\currentitemgroup{\currentparentitemgroup:\currentitemlevel}%
    %
    \edef\p_itemgroups_options{\itemgroupparameter\c!option}%
-   \let\p_itemgroups_extra_options\empty
+   \lettonothing\p_itemgroups_extra_options
    \ifcase\nofarguments
      \strc_itemgroups_start_indeed{}%
    \or
@@ -937,11 +944,11 @@
    \fi\fi
    \ifconditional\c_strc_itemgroups_paragraph
      \ifnum\c_strc_itemgroups_nesting>\plusone
-       \letitemgroupparameter\c!inbetween\empty
+       \resetitemgroupparameter\c!inbetween
      \fi
    \fi
    \ifconditional\c_strc_itemgroups_pack
-     \letitemgroupparameter\c!inbetween\empty
+     \resetitemgroupparameter\c!inbetween
    \fi
    \ifconditional\c_strc_itemgroups_columns
      \ifinsidecolumns\orelse\ifcase\c_strc_itemgroups_column_depth
@@ -1159,7 +1166,7 @@
 %     \stopitemize
 % \stopitemize
 
-\mutable\let\currentitemreference\empty
+\mutable\lettonothing\currentitemreference
 
 \tolerant\permanent\protected\def\startitemgroupitem[#reference]% we can reuse more
   {\def\currentitemreference{#reference}%
@@ -1270,7 +1277,7 @@
   {\startitemgroupitem}
 
 \protected\def\strc_itemgroups_start_no_item
-  {\let\currentitemreference\empty
+  {\lettonothing\currentitemreference
    \strc_itemgroups_increment_item_counter
   %\advance\c_strc_itemgroups_n_of_items\plusone
    \setbox\b_strc_itemgroups\emptyhbox
@@ -1462,7 +1469,7 @@
           \strc_itemgroups_used_symbol
         \fi
       \fi}%
-   \let\strc_itemgroups_extra_symbol\empty
+   \lettonothing\strc_itemgroups_extra_symbol
    \setfalse\c_strc_itemgroups_symbol}
 
 \def\strc_itemgroups_make_fitting_box
@@ -1504,7 +1511,7 @@
        \edef\m_strc_itemgroups_repeat_start{\currentitemlevel}%
      \fi
    \else
-     \let\m_strc_itemgroups_repeat_start\empty
+     \lettonothing\m_strc_itemgroups_repeat_start
    \fi}
 
 \def\strc_itemgroups_insert_item
@@ -1527,7 +1534,7 @@
    \orelse\ifdim\d_strc_itemgroups_asked_width>\zeropoint
      \strc_itemgroups_make_aligned_box
    \fi
-   \let\m_strc_itemgroups_destination\empty
+   \lettonothing\m_strc_itemgroups_destination
    \ht\b_strc_itemgroups\strutheight % just in case a symbols is not yet available in
    \dp\b_strc_itemgroups\strutdepth  % the current run (more a mkii mp side artifact)
    \strc_itemgroups_check_for_repeated
@@ -1557,7 +1564,7 @@
    \ignorepars} % \ignorespaces
 
 \def\strc_itemgroups_start_item_nop
-  {\let\currentitemreference\empty
+  {\lettonothing\currentitemreference
    \strc_itemgroups_increment_item_counter
    \advance\c_strc_itemgroups_n_of_items\plusone
    \setbox\b_strc_itemgroups\hbox
@@ -1713,7 +1720,7 @@
 
 \let\strc_itemgroups_collected_store\relax
 
-\let\m_strc_itemgroups_collected\empty
+\lettonothing\m_strc_itemgroups_collected
 
 \normalexpanded{\def\strc_itemgroups_collected_store#1\csname\e!stop\v!item\endcsname}%
   {\advance\c_strc_itemgroups_collected_stored\plusone
@@ -1844,7 +1851,7 @@
    %letitemgroupparameter\c!width\zeropoint
    \strc_itemgroups_make_symbol_box
    \strc_itemgroups_make_destination_box
-   \let\m_strc_itemgroups_destination\empty
+   \lettonothing\m_strc_itemgroups_destination
    \ht\b_strc_itemgroups\strutheight
    \dp\b_strc_itemgroups\strutdepth
    \box\b_strc_itemgroups
diff --git a/tex/context/base/mkxl/strc-lab.mkxl b/tex/context/base/mkxl/strc-lab.mkxl
index 368a412a7..98bd390f9 100644
--- a/tex/context/base/mkxl/strc-lab.mkxl
+++ b/tex/context/base/mkxl/strc-lab.mkxl
@@ -71,10 +71,10 @@
 
 % todo: \strc_labels_command for user
 
-\let\m_strc_labels_sub\empty
+\lettonothing\m_strc_labels_sub
 
 \appendtoks
-    \let\m_strc_labels_sub\empty
+    \lettonothing\m_strc_labels_sub
     \ifempty\currentlabelparent
        % clone => parent | subclone => clone | subsubclone => subclone
        \strc_define_commands_label
@@ -106,8 +106,8 @@
    \letlabelparameter\s!counter\p_counter
 \to \everydefinelabel
 
-\let\p_strc_constructions_title \empty
-\let\p_strc_constructions_number\empty
+\lettonothing\p_strc_constructions_title
+\lettonothing\p_strc_constructions_number
 
 \newconditional\c_strc_constructions_number_keep
 
diff --git a/tex/context/base/mkxl/strc-lnt.mklx b/tex/context/base/mkxl/strc-lnt.mklx
index d88227bc5..31a558a06 100644
--- a/tex/context/base/mkxl/strc-lnt.mklx
+++ b/tex/context/base/mkxl/strc-lnt.mklx
@@ -87,7 +87,7 @@
 
 % maybe do this in lua
 
-\mutable\let\currentlinenotereference\empty
+\mutable\lettonothing\currentlinenotereference
 
 \def\page_lines_in_from{\in[lr:b:\currentlinenotereference]}
 \def\page_lines_in_to  {\in[lr:e:\currentlinenotereference]}
@@ -136,7 +136,7 @@
      \fi
    \fi}
 
-\let\currentlinenotereference\empty
+\lettonothing\currentlinenotereference
 
 \mutable\let\linenotelinenumber\relax
 
diff --git a/tex/context/base/mkxl/strc-lst.mklx b/tex/context/base/mkxl/strc-lst.mklx
index c04d68fa7..e14f0c735 100644
--- a/tex/context/base/mkxl/strc-lst.mklx
+++ b/tex/context/base/mkxl/strc-lst.mklx
@@ -258,7 +258,7 @@
       % use settings of first
    \else
       % use settings of root
-      \let\m_first\empty
+      \lettonothing\m_first
    \fi
    \strc_lists_place_indeed\m_first\m_list{#settings}%
    \stoppacked
@@ -271,7 +271,7 @@
 
 \def\strc_lists_place_indeed#tag#list#settings%
   {\begingroup
-   \the\t_lists_every_renderingcleanup % \let\currentlistentrylocation\empty
+   \the\t_lists_every_renderingcleanup % \lettonothing\currentlistentrylocation
    \edef\currentlist{#tag}%
    \setupcurrentlist[#settings]%
    \the\everystructurelist
@@ -523,7 +523,7 @@
 
 \permanent\protected\def\strclistsentryprocess#tag#method#index#extra% This one is called at the lua end!
   {\clf_pushlist#index\relax
-  %\let\currentlistentrylocation\empty
+  %\lettonothing\currentlistentrylocation
    \edef\currentlist      {#tag}%
    \edef\currentlistmethod{#method}%
    \edef\currentlistindex {#index}%
@@ -627,7 +627,8 @@
    \rightlabeltext\currentlistlabel}
 
 \mutable\let\currentlistnumber\!!zerocount
-\mutable\let\currentlistlabel \empty
+
+\mutable\lettonothing\currentlistlabel
 
 \protected\def\strc_lists_symbol_default
   {\dontleavehmode
@@ -852,10 +853,10 @@
 \newconditional\c_lists_show_number
 \newconditional\c_lists_show_page
 
-\mutable\let\currentlistentrylocation  \empty % watch the 'entry' in the name
-\mutable\let\currentlistentrynumber    \empty % watch the 'entry' in the name
-\mutable\let\currentlistentrytitle     \empty % watch the 'entry' in the name
-\mutable\let\currentlistentrypagenumber\empty % watch the 'entry' in the name
+\mutable\lettonothing\currentlistentrylocation   % watch the 'entry' in the name
+\mutable\lettonothing\currentlistentrynumber     % watch the 'entry' in the name
+\mutable\lettonothing\currentlistentrytitle      % watch the 'entry' in the name
+\mutable\lettonothing\currentlistentrypagenumber % watch the 'entry' in the name
 
 \appendtoks
     \dontcomplain
@@ -918,10 +919,10 @@
 \appendtoks
    % as we don't want any interference we clear some variables
    % afterwards
-   \let\currentlistentrylocation  \empty
-   \let\currentlistentrynumber    \empty
-   \let\currentlistentrytitle     \empty
-   \let\currentlistentrypagenumber\empty
+   \lettonothing\currentlistentrylocation
+   \lettonothing\currentlistentrynumber
+   \lettonothing\currentlistentrytitle
+   \lettonothing\currentlistentrypagenumber
    \setfalse\c_lists_has_page
    \setfalse\c_lists_has_number
    \setfalse\c_lists_show_page
@@ -929,7 +930,7 @@
    \setfalse\c_lists_show_number
 \to \t_lists_every_renderingcleanup
 
-\let\m_strc_list_alternative\empty % combined
+\lettonothing\m_strc_list_alternative % combined
 
 \protected\def\strc_lists_apply_renderingsetup
   {\the\t_lists_every_renderingsetup
@@ -1247,8 +1248,8 @@
     \noindent % otherwise annotations are mirrored up
     \typo_injectors_mark_list
     \hbox \strc_lists_get_reference_attribute\v!all \strc_lists_get_destination_attribute {
-        \letlistparameter\c!depth\zeropoint
-        \letlistparameter\c!color\empty
+        \letlistparameter   \c!depth\zeropoint
+        \resettlistparameter\c!color
         \inheritedlistframed {
             \letinteractionparameter\c!strut\v!no % still needed?
             \strc_lists_set_style_color\c!style\c!color\v!all
@@ -1475,8 +1476,8 @@
      \a_strc_lists_destination\attributeunsetvalue
    \fi
    \ifnum\a_strc_lists_destination=\attributeunsetvalue
-     \let\strc_lists_get_destination_attribute\empty
-     \let\strc_lists_set_destination_attribute\empty
+     \lettonothing\strc_lists_get_destination_attribute
+     \lettonothing\strc_lists_set_destination_attribute
    \else
      \let\strc_lists_get_destination_attribute\strc_lists_get_destination_attribute_indeed
      \let\strc_lists_set_destination_attribute\strc_lists_set_destination_attribute_indeed
@@ -1487,8 +1488,8 @@
    \a_strc_lists_destination\attributeunsetvalue
    \let\strc_lists_get_reference_attribute\gobbleoneargument
    \let\strc_lists_set_reference_attribute\gobbleoneargument
-   \let\strc_lists_get_destination_attribute\empty
-   \let\strc_lists_set_destination_attribute\empty
+   \lettonothing\strc_lists_get_destination_attribute
+   \lettonothing\strc_lists_set_destination_attribute
    \let\strc_lists_set_style_color\strc_lists_set_style_color_normal}
 
 \def\strc_lists_interaction_check_yes
@@ -1503,8 +1504,8 @@
 \def\strc_lists_interaction_check_nop
   {\let\strc_lists_get_reference_attribute  \gobbleoneargument
    \let\strc_lists_set_reference_attribute  \gobbleoneargument
-   \let\strc_lists_get_destination_attribute\empty
-   \let\strc_lists_set_destination_attribute\empty
+   \lettonothing\strc_lists_get_destination_attribute
+   \lettonothing\strc_lists_set_destination_attribute
    \let\strc_lists_set_style_color          \strc_lists_set_style_color_normal}
 
 \strc_lists_interaction_check_nop
diff --git a/tex/context/base/mkxl/strc-mat.mkxl b/tex/context/base/mkxl/strc-mat.mkxl
index 90321a627..bac25c520 100644
--- a/tex/context/base/mkxl/strc-mat.mkxl
+++ b/tex/context/base/mkxl/strc-mat.mkxl
@@ -181,7 +181,7 @@
 \newtoks\everyresetformulas
 
 \appendtoks
-    \let\currentformula\empty % to be checked:
+    \lettonothing\currentformula % to be checked:
 \to \everyresetformulas
 
 % implementation
@@ -199,7 +199,7 @@
       \c!list=\currentplaceformulalist,
       \c!bookmark=\currentplaceformulabookmark]%
      [#2]%
-   \glet\namedformulaentry\empty % \relax
+   \glettonothing\namedformulaentry % \relax
    \glet#3\m_strc_counters_last_registered_index
    \glet#4\m_strc_counters_last_registered_synchronize
    \glet#5\m_strc_counters_last_registered_attribute}
@@ -388,30 +388,30 @@
 \mutable\let\currentsubformulanumber  \relax
 \mutable\let\currentformulasnumber    \relax
 
-\mutable\let\currentformulasreference     \empty
-\mutable\let\currentformulareference      \empty
-\mutable\let\currentsubformulareference   \empty
-\mutable\let\currentnestedformulanumber   \empty
-\mutable\let\currentnestedformulareference\empty
-\mutable\let\currentnestedformulaattribute\empty
+\mutable\lettonothing\currentformulasreference
+\mutable\lettonothing\currentformulareference
+\mutable\lettonothing\currentsubformulareference
+\mutable\lettonothing\currentnestedformulanumber
+\mutable\lettonothing\currentnestedformulareference
+\mutable\lettonothing\currentnestedformulaattribute
 
 \appendtoks
-    \glet\currentformulasreference     \empty
-    \glet\currentformulareference      \empty
-    \glet\currentsubformulareference   \empty
-    \glet\currentnestedformulareference\empty
+    \glettonothing\currentformulasreference
+    \glettonothing\currentformulareference
+    \glettonothing\currentsubformulareference
+    \glettonothing\currentnestedformulareference
 \to \everyresetformulas
 
-\mutable\let\currentformulassuffix     \empty
-\mutable\let\currentformulasuffix      \empty
-\mutable\let\currentsubformulasuffix   \empty
-\mutable\let\currentnestedformulasuffix\empty
+\mutable\lettonothing\currentformulassuffix
+\mutable\lettonothing\currentformulasuffix
+\mutable\lettonothing\currentsubformulasuffix
+\mutable\lettonothing\currentnestedformulasuffix
 
 \appendtoks
-    \glet\currentformulassuffix     \empty
-    \glet\currentformulasuffix      \empty
-    \glet\currentsubformulasuffix   \empty
-    \glet\currentnestedformulasuffix\empty
+    \glettonothing\currentformulassuffix
+    \glettonothing\currentformulasuffix
+    \glettonothing\currentsubformulasuffix
+    \glettonothing\currentnestedformulasuffix
 \to \everyresetformulas
 
 \mutable\let\currentplaceformulasynchronize \relax
@@ -426,10 +426,10 @@
     \glet\currentnestedformulasynchronize\relax
 \to \everyresetformulas
 
-\mutable\let\currentsubformulasattribute  \empty
-\mutable\let\currentsubformulasnumber     \empty
-\mutable\let\currentsubformulasreference  \empty
-\mutable\let\currentsubformulassynchronize\empty
+\mutable\lettonothing\currentsubformulasattribute
+\mutable\lettonothing\currentsubformulasnumber
+\mutable\lettonothing\currentsubformulasreference
+\mutable\lettonothing\currentsubformulassynchronize
 
 \def\strc_formulas_handle_current_references
   {\strc_formulas_reference_show
@@ -494,8 +494,8 @@
 %         \fi
 %         \strc_counters_increment\v!formula}%
 %    \fi
-%    \glet\currentplaceformulasuffix\empty
-%    \glet\currentnestedformulasuffix\empty
+%    \glettonothing\currentplaceformulasuffix
+%    \glettonothing\currentnestedformulasuffix
 %    \placecurrentformulanumber}
 
 \def\strc_formulas_handle_numbering_indeed
@@ -517,8 +517,8 @@
         \fi
         \strc_counters_increment\v!formula}%
    \fi
-   \glet\currentplaceformulasuffix\empty
-   \glet\currentnestedformulasuffix\empty
+   \glettonothing\currentplaceformulasuffix
+   \glettonothing\currentnestedformulasuffix
    \placecurrentformulanumber}
 
 \def\strc_formulas_handle_numbering
@@ -535,8 +535,8 @@
    \doifelsetext\currentnestedformulasuffix
      {\strc_counters_setown_sub\v!formula\plustwo\currentnestedformulasuffix}%
      {\strc_counters_increment_sub\v!formula\plustwo}%
-   \glet\currentplaceformulasuffix\empty
-   \glet\currentnestedformulasuffix\empty
+   \glettonothing\currentplaceformulasuffix
+   \glettonothing\currentnestedformulasuffix
    \placecurrentformulanumber}
 
 \def\strc_formulas_handle_sub_numbering
@@ -684,7 +684,7 @@
 
 \newconstant\c_strc_math_split_mode
 
-\mutable\let\m_strc_math_split\empty
+\mutable\lettonothing\m_strc_math_split
 
 \aliased\let\c_strc_math_line_mode\zerocount
 \aliased\let\c_strc_math_flow_mode\plusone
@@ -698,7 +698,7 @@
 
 \def\strc_formulas_display_space_before_normal
   {% not ok, try \stopformula\par\startformula vs \stopformula\startformula
-   \let\m_spacebefore\empty
+   \lettonothing\m_spacebefore
    \ifvmode
      \ifdim\lastskip>\zeropoint\else
        \ifdim\prevdepth<\zeropoint\else
@@ -797,7 +797,7 @@
    \fi
    \ifvmode
      \ifconditional\c_strc_formulas_packed
-       \let\p_spacebefore\empty
+       \lettonothing\p_spacebefore
      \else
        \edef\p_spacebefore{\formulaparameter\c!spacebefore}%
      \fi
@@ -815,7 +815,7 @@
    \fi
    \ifvmode
      \ifconditional\c_strc_formulas_packed
-       \let\p_spaceafter\empty
+       \lettonothing\p_spaceafter
      \else
        \edef\p_spaceafter{\formulaparameter\c!spaceafter}%
      \fi
@@ -1672,8 +1672,8 @@
 
 % already defined
 %
-% \let\startinnermath\empty
-% \let\stopinnermath \empty
+% \lettonothing\startinnermath
+% \lettonothing\stopinnermath
 
 % \defineformulaalternative[multi][\begindmath][\enddmath]
 %
@@ -1758,7 +1758,7 @@
    \global\settrue\c_strc_formulas_inside_formulas
    \edef\currentformulasreference{#1}%
    \strc_formulas_handle_number
-   \let\currentformula\empty
+   \lettonothing\currentformula
  % \strc_formulas_forget_display_skips
    \enforced\protected\def\startformula
      {\advance\scratchcounter\plusone
@@ -1808,8 +1808,8 @@
 
 \tolerant\protected\def\strc_formulas_place[#1]%
   {\xdef\currentplaceformulareference{#1}%
-   \glet\currentplaceformulasuffix\empty
-   \glet\currentnestedformulasuffix\empty
+   \glettonothing\currentplaceformulasuffix
+   \glettonothing\currentnestedformulasuffix
    \global\setfalse\c_strc_formulas_incremented
    \global\setfalse\c_strc_formulas_referenced
    \global\settrue\c_strc_formulas_inside_place
@@ -1839,9 +1839,9 @@
 % \startplaceformula[title=whatever] \startformula e=mc^2 \stopformula \stopplaceformula
 % \startplaceformula[suffix=x]       \startformula e=mc^2 \stopformula \stopplaceformula
 
-\mutable\let\currentplaceformulatitle    \empty
-\mutable\let\currentplaceformulareference\empty
-\mutable\let\currentplaceformulasuffix   \empty
+\mutable\lettonothing\currentplaceformulatitle
+\mutable\lettonothing\currentplaceformulareference
+\mutable\lettonothing\currentplaceformulasuffix
 
 \permanent\tolerant\protected\def\startplaceformula[#1]%
   {\begingroup
@@ -1858,25 +1858,25 @@
   {\doifassignmentelse{#1}\strc_formulas_start_place_parameters\strc_formulas_start_place_reference[#1]}
 
 \def\strc_formulas_start_place_nop[#1]%
-  {\glet\currentplaceformulareference\empty
-   \glet\currentplaceformulasuffix   \empty
+  {\glettonothing\currentplaceformulareference
+   \glettonothing\currentplaceformulasuffix
    \strc_formulas_place_nop}
 
 \def\strc_formulas_start_place_reference[#1]%
   {\xdef\currentplaceformulareference{#1}%
-   \glet\currentplaceformulasuffix\empty
+   \glettonothing\currentplaceformulasuffix
   %\doifelsenextbgroup\strc_formulas_place_yes\strc_formulas_place_nop} % [ref]{}
    \strc_formulas_place_nop}
 
-\mutable\let\currentplaceformulabookmark\empty
-\mutable\let\currentplaceformulalist    \empty
+\mutable\lettonothing\currentplaceformulabookmark
+\mutable\lettonothing\currentplaceformulalist
 
 \def\strc_formulas_start_place_parameters[#1]% maybe a dedicated setup handler
-  {\letdummyparameter\c!title    \empty
-   \letdummyparameter\c!reference\empty
-   \letdummyparameter\c!bookmark \empty
-   \letdummyparameter\c!list     \empty
-   \letdummyparameter\c!suffix   \empty
+  {\resetdummyparameter\c!title
+   \resetdummyparameter\c!reference
+   \resetdummyparameter\c!bookmark
+   \resetdummyparameter\c!list
+   \resetdummyparameter\c!suffix
    \getdummyparameters[#1]%
    \edef\currentplaceformulatitle    {\dummyparameter\c!title}%
    \edef\currentplaceformulareference{\dummyparameter\c!reference}%
@@ -1904,13 +1904,13 @@
      \xdef\currentnestedformulasuffix   {\mathalignmentparameter\c!suffix}%
      \global\d_math_eqalign_number_threshold\mathalignmentparameter\c!numberthreshold\relax
    \orelse\ifhastok+{#1}%
-     \glet\currentnestedformulareference\empty
+     \glettonothing\currentnestedformulareference
      \xdef\currentnestedformulasuffix   {+}%
    \orelse\ifempty\currentplaceformulareference
      \xdef\currentnestedformulareference{#1}%
      \xdef\currentnestedformulasuffix   {#2}%
    \else
-     \glet\currentnestedformulareference\empty
+     \glettonothing\currentnestedformulareference
      \xdef\currentnestedformulasuffix   {#1}%
    \fi
    \strc_formulas_place_number_nested_check}
@@ -1991,7 +1991,7 @@
    \hskip-\leftskip % bah
    \box\b_strc_math_display}
 
-\mutable\let\namedformulaentry\empty % \relax % this will become a key/value so that we can do bookmarks
+\mutable\lettonothing\namedformulaentry % \relax % this will become a key/value so that we can do bookmarks
 
 \permanent\protected\def\setformulalistentry#1%
   {\xdef\namedformulaentry{#1}}
diff --git a/tex/context/base/mkxl/strc-not.mklx b/tex/context/base/mkxl/strc-not.mklx
index fbe45b2e8..76c95ab18 100644
--- a/tex/context/base/mkxl/strc-not.mklx
+++ b/tex/context/base/mkxl/strc-not.mklx
@@ -146,10 +146,10 @@
    \instance\protected\edefcsname\e!start#tag\endcsname{\strc_notations_start[#tag]}%
    \instance\protected\edefcsname\e!stop #tag\endcsname{\strc_notations_stop}}
 
-\let\m_strc_notation_sub\empty
+\lettonothing\m_strc_notation_sub
 
 \appendtoks
-    \let\m_strc_notation_sub\empty
+    \lettonothing\m_strc_notation_sub
     \ifempty\currentnotationparent
        % clone => parent | subclone => clone | subsubclone => subclone
        \strc_define_commands_notation
@@ -184,8 +184,8 @@
   %\strc_notes_setup_counter\currentnotation
 \to \everydefinenotation
 
-\let\p_strc_constructions_title \empty
-\let\p_strc_constructions_number\empty
+\lettonothing\p_strc_constructions_title
+\lettonothing\p_strc_constructions_number
 
 \protected\defcsname\??constructioninitializer\v!notation\endcsname
   {\let         \currentnotation                 \currentconstruction
@@ -544,8 +544,8 @@
 \newconstant\a_strc_notes_text_reference
 \newconstant\a_strc_notes_text_destination
 
-\let\strc_notes_get_reference_attribute_symbol  \empty
-\let\strc_notes_get_destination_attribute_symbol\empty
+\lettonothing\strc_notes_get_reference_attribute_symbol
+\lettonothing\strc_notes_get_destination_attribute_symbol
 
 \def\strc_notes_interaction_check_inline
   {\edef\p_interaction{\noteparameter\c!interaction}%
@@ -561,8 +561,8 @@
 
 \mutable\let\currentnotenumber\!!zerocount
 
-\let\strc_notes_get_reference_attribute_symbol  \empty
-\let\strc_notes_get_destination_attribute_symbol\empty
+\lettonothing\strc_notes_get_reference_attribute_symbol
+\lettonothing\strc_notes_get_destination_attribute_symbol
 
 \let\strc_notes_set_reference_attribute_number\donothing
 \let\strc_notes_set_reference_attribute_text  \donothing
@@ -576,8 +576,8 @@
 \let\m_strc_notes_internal\relax
 
 \def\strc_notes_prepare_inline_references_nop
-  {\let\strc_notes_get_reference_attribute_symbol\empty
-   \let\strc_notes_get_destination_attribute_symbol\empty
+  {\lettonothing\strc_notes_get_reference_attribute_symbol
+   \lettonothing\strc_notes_get_destination_attribute_symbol
    \let\strc_notes_set_style_color_inline\strc_notes_set_style_color_inline_nop}
 
 \def\strc_notes_prepare_inline_references_yes
@@ -727,7 +727,7 @@
      \dostoptagged
    \egroup
    \endgroup
-   \glet\lastnotesymbol\empty}
+   \glettonothing\lastnotesymbol}
 
 \protected\def\strc_notes_inject_dummy % temp hack
   {\removeunwantedspaces
@@ -739,7 +739,7 @@
    \fi
    \nobreak
    \hpack to .5\emwidth{}%
-   \glet\lastnotesymbol\empty}
+   \glettonothing\lastnotesymbol}
 
 \protected\def\strc_notes_inject_separator % patch by WS due to request on list
   {\edef\p_textseparator{\noteparameter\c!textseparator}%
@@ -1630,7 +1630,7 @@
 
 \newconditional\inlocalnotes
 
-\mutable\let\localnoteslist\empty
+\mutable\lettonothing\localnoteslist
 
 \permanent\tolerant\protected\def\startlocalnotes[#list]% grouping ? (we used to have a second argument ... settings)
   {\settrue\inlocalnotes
@@ -1641,7 +1641,7 @@
   {\processcommacommand[\localnoteslist]\strc_notes_local_stop_step
    \setfalse\inlocalnotes}
 
-\let\p_strc_notes_continue\empty
+\lettonothing\p_strc_notes_continue
 
 \def\strc_notes_local_start_step#tag%
   {\p_strc_notes_continue{\noteparameter\c!continue}%
@@ -1974,7 +1974,7 @@
 
 \installcorenamespace{notesymbol}
 
-\mutable\let\lastnotesymbol\empty % todo: per class
+\mutable\lettonothing\lastnotesymbol % todo: per class
 
 \permanent\tolerant\protected\def\notesymbol[#tag]#keepspacer[#reference]%
   {\ifnotesenabled
diff --git a/tex/context/base/mkxl/strc-num.mkxl b/tex/context/base/mkxl/strc-num.mkxl
index f0735b0e5..3f3bd2143 100644
--- a/tex/context/base/mkxl/strc-num.mkxl
+++ b/tex/context/base/mkxl/strc-num.mkxl
@@ -70,7 +70,7 @@
         \edef\p_number{\counterparameter\c!number}%
         \ifempty\p_number \else
           \clf_setcounter{\counterparameter\s!name}\numexpr\p_number\relax
-          \letcounterparameter\c!number\empty
+          \resetcounterparameter\c!number
         \fi
         \edef\p_start{\counterparameter\c!start}%
         \setexpandedcounterparameter\c!start{\ifempty\p_start0\else\number\p_start\fi}%
@@ -378,8 +378,8 @@
 
 % currentstructurecomponent => \strc_current_ or just \m_strc_
 
-\mutable\let\currentname   \empty
-\mutable\let\currentcounter\empty
+\mutable\lettonothing\currentname
+\mutable\lettonothing\currentcounter
 
 \protected\def\strc_counters_register_component#1#2#3#4#5#6#7[#8][#9]% maybe also nolist
   {\begingroup
@@ -426,7 +426,7 @@
      \let\currentstructurecomponentreferenceprefix\referenceprefix
    \fi
    \ifdefined\currentstructurecomponentreferenceprefix\else
-     \let\currentstructurecomponentreferenceprefix\empty
+     \lettonothing\currentstructurecomponentreferenceprefix
    \fi}
 
 \def\strc_counters_register_component_page#1%
@@ -666,7 +666,7 @@
 %       \ifempty#2%
 %         \the#5%
 %       \else
-%         \let\currentcounter\empty
+%         \lettonothing\currentcounter
 %         \the\everysetupcounter
 %       \fi
 %       \strc_counter_setup_pop}%
@@ -688,7 +688,7 @@
 %         \edef\p_number{\counterparameter\c!number}%
 %         \ifempty\p_number \else
 %             \strc_counters_set\currentcounter\p_number
-%             \letcounterparameter\c!number\empty
+%             \resetcounterparameter\c!number
 %         \fi
 %     \fi
 % \to \everysetupcounter
diff --git a/tex/context/base/mkxl/strc-ref.mklx b/tex/context/base/mkxl/strc-ref.mklx
index 012d9d92d..c55509f54 100644
--- a/tex/context/base/mkxl/strc-ref.mklx
+++ b/tex/context/base/mkxl/strc-ref.mklx
@@ -70,28 +70,28 @@
 
 \installdirectcommandhandler \??referencing {referencing} % \??referencing
 
-\mutable\let\referenceprefix               \empty
-
-\mutable\let\currentdestinationattribute   \empty
-
-\mutable\let\currentreferenceattribute     \empty
-\mutable\let\currentreferencecoding        \empty
-\mutable\let\currentreferencecontent       \empty
-\mutable\let\currentreferencedata          \empty
-\mutable\let\currentreferenceexpansion     \empty
-\mutable\let\currentreferenceformatautocase\empty
-\mutable\let\currentreferenceformatlabel   \empty
-\mutable\let\currentreferenceformatsetups  \empty
-\mutable\let\currentreferenceformattype    \empty
-\mutable\let\currentreferencekind          \empty
-\mutable\let\currentreferencelabels        \empty
-%mutable\let\currentreferencenumber        \empty
-%mutable\let\currentreferenceorder         \empty
-%mutable\let\currentreferencepage          \empty
-%mutable\let\currentreferencerealpage      \empty
-%mutable\let\currentreferencetext          \empty
-%mutable\let\currentreferencetitle         \empty
-\mutable\let\currentreferenceuserdata      \empty
+\mutable\lettonothing\referenceprefix
+
+\mutable\lettonothing\currentdestinationattribute
+
+\mutable\lettonothing\currentreferenceattribute
+\mutable\lettonothing\currentreferencecoding
+\mutable\lettonothing\currentreferencecontent
+\mutable\lettonothing\currentreferencedata
+\mutable\lettonothing\currentreferenceexpansion
+\mutable\lettonothing\currentreferenceformatautocase
+\mutable\lettonothing\currentreferenceformatlabel
+\mutable\lettonothing\currentreferenceformatsetups
+\mutable\lettonothing\currentreferenceformattype
+\mutable\lettonothing\currentreferencekind
+\mutable\lettonothing\currentreferencelabels
+%mutable\lettonothing\currentreferencenumber
+%mutable\lettonothing\currentreferenceorder
+%mutable\lettonothing\currentreferencepage
+%mutable\lettonothing\currentreferencerealpage
+%mutable\lettonothing\currentreferencetext
+%mutable\lettonothing\currentreferencetitle
+\mutable\lettonothing\currentreferenceuserdata
 
 \newif\ifreferencing \referencingtrue
 
@@ -375,7 +375,7 @@
    \ifnum\lastdestinationattribute>\zerocount
      \edef#cs{attr \destinationattribute\number\lastdestinationattribute}%
    \else
-     \let#cs\empty
+     \lettonothing#cs%
    \fi}
 
 %D It's about time to clean up references .. stable enough now.
@@ -542,7 +542,7 @@
 %D one keeps references local, but the global ones in view. To enable this feature,
 %D we explictly split the prefix from the reference.
 
-\let\referenceprefix\empty
+\lettonothing\referenceprefix
 
 %D For a long time the only way to access an external file was to use the file
 %D prefix (\type {somefile::}. However, when you split up a document, redefining the
@@ -580,11 +580,11 @@
 %D
 %D We also use the odd/even characteristic to determine the page state.
 
-\mutable\let\currentrealreference      \empty
-\mutable\let\currentpagereference      \empty
-\mutable\let\currenttextreference      \empty
-\mutable\let\currentsubtextreference   \empty
-\mutable\let\currentsubsubtextreference\empty
+\mutable\lettonothing\currentrealreference
+\mutable\lettonothing\currentpagereference
+\mutable\lettonothing\currenttextreference
+\mutable\lettonothing\currentsubtextreference
+\mutable\lettonothing\currentsubsubtextreference
 
 % referencepagestate:
 %
@@ -923,14 +923,14 @@
 \permanent\protected\def\setupreferenceprefix[#prefix]%
   {\edef\p_prefix{#prefix}%
    \ifempty\p_prefix
-     \let\referenceprefix\empty
+     \lettonothing\referenceprefix
    \orelse\ifx\p_prefix\m_strc_references_prefix_yes
      \letreferencingparameter\c!prefix\s!unknown
      \global\advance\prefixcounter\plusone
      \edef\referenceprefix{\the\prefixcounter}%
    \orelse\ifx\p_prefix\m_strc_references_prefix_nop
      \letreferencingparameter\c!prefix\s!unknown
-     \let\referenceprefix\empty
+     \lettonothing\referenceprefix
    \orelse\ifx\p_prefix\s!unknown
      % forget about it
    \else
@@ -1217,9 +1217,9 @@
 \newtoks\defaultleftreferencetoks
 \newtoks\defaultrightreferencetoks
 
-\permanent\let\rightofreferencecontent\empty
-\permanent\let\leftofreference        \empty
-\permanent\let\rightofreference       \empty
+\permanent\lettonothing\rightofreferencecontent
+\permanent\lettonothing\leftofreference
+\permanent\lettonothing\rightofreference
 
 \permanent\protected\def\leftofreferencecontent
   {\removeunwantedspaces
@@ -1284,14 +1284,14 @@
        {#1}%
      \else
        \defaultleftreferencetoks
-       \enforced\let\leftofreferencecontent\empty
+       \enforced\lettonothing\leftofreferencecontent
      \fi
    \rightreferencetoks
      \ifparameter#2\or
        {#2}%
      \else
        \defaultrightreferencetoks
-       \enforced\let\rightofreferencecontent\empty
+       \enforced\lettonothing\rightofreferencecontent
      \fi
    % inefficient: double resolve
    \doifelsereferencefound{#3} % we need to resolve the text
@@ -1411,8 +1411,8 @@
      \def\currentreferencecontent{\directsetup\currentreferenceformatsetups}%
    \fi
    %
-   \enforced\let\leftofreferencecontent \empty
-   \enforced\let\rightofreferencecontent\empty
+   \enforced\lettonothing\leftofreferencecontent
+   \enforced\lettonothing\rightofreferencecontent
    \strc_references_pickup_goto}
 
 \permanent\protected\def\autoreferencelabeltext
diff --git a/tex/context/base/mkxl/strc-reg.mkxl b/tex/context/base/mkxl/strc-reg.mkxl
index b0f50ecfd..3af07f0a4 100644
--- a/tex/context/base/mkxl/strc-reg.mkxl
+++ b/tex/context/base/mkxl/strc-reg.mkxl
@@ -138,33 +138,33 @@
 %D test \index{test+one} test \index{test+two} more \index{more}
 %D \stoptyping
 
-\mutable\let\currentregistercharacter   \empty
-\mutable\let\currentregistercoding      \empty
-\mutable\let\currentregisterentries     \empty
-\mutable\let\currentregisterentriesa    \empty
-\mutable\let\currentregisterentriesb    \empty
-\mutable\let\currentregisterentriesc    \empty
-\mutable\let\currentregisterexpansion   \empty
-\mutable\let\currentregisterkeys        \empty
-\mutable\let\currentregisterkeysa       \empty
-\mutable\let\currentregisterkeysb       \empty
-\mutable\let\currentregisterkeysc       \empty
-\mutable\let\currentregisterlabel       \empty
-\mutable\let\currentregistermaxwidth    \empty
-\mutable\let\currentregistername        \empty
-\mutable\let\currentregisternumber      \empty
-\mutable\let\currentregisterownnumber   \empty
-\mutable\let\currentregisterpageindex   \empty
-\mutable\let\currentregisterpagesymbol  \empty
-\mutable\let\currentregistersectionindex\empty
-\mutable\let\currentregisterseeindex    \empty
-\mutable\let\currentregisterseeword     \empty
-\mutable\let\currentregistersynchronize \empty
-\mutable\let\currentregisterxmlsetup    \empty
-\mutable\let\currentregisterprocessors  \empty
-\mutable\let\currentregisterprocessorsa \empty
-\mutable\let\currentregisterprocessorsb \empty
-\mutable\let\currentregisterprocessorsc \empty
+\mutable\lettonothing\currentregistercharacter
+\mutable\lettonothing\currentregistercoding
+\mutable\lettonothing\currentregisterentries
+\mutable\lettonothing\currentregisterentriesa
+\mutable\lettonothing\currentregisterentriesb
+\mutable\lettonothing\currentregisterentriesc
+\mutable\lettonothing\currentregisterexpansion
+\mutable\lettonothing\currentregisterkeys
+\mutable\lettonothing\currentregisterkeysa
+\mutable\lettonothing\currentregisterkeysb
+\mutable\lettonothing\currentregisterkeysc
+\mutable\lettonothing\currentregisterlabel
+\mutable\lettonothing\currentregistermaxwidth
+\mutable\lettonothing\currentregistername
+\mutable\lettonothing\currentregisternumber
+\mutable\lettonothing\currentregisterownnumber
+\mutable\lettonothing\currentregisterpageindex
+\mutable\lettonothing\currentregisterpagesymbol
+\mutable\lettonothing\currentregistersectionindex
+\mutable\lettonothing\currentregisterseeindex
+\mutable\lettonothing\currentregisterseeword
+\mutable\lettonothing\currentregistersynchronize
+\mutable\lettonothing\currentregisterxmlsetup
+\mutable\lettonothing\currentregisterprocessors
+\mutable\lettonothing\currentregisterprocessorsa
+\mutable\lettonothing\currentregisterprocessorsb
+\mutable\lettonothing\currentregisterprocessorsc
 
 \newconditional\c_strc_registers_defining
 \setnewconstant\c_strc_registers_maxlevel \plusfive
@@ -188,8 +188,8 @@
       \dorecurse\c_strc_registers_maxlevel{% weird, expanded should not be needed
         \normalexpanded{\defineregister[\currentregister:\recurselevel][\currentregister]}%
        %\defineregister[\currentregister:\recurselevel][\currentregister]%
-        \letregisterparameter{\c!entries:\recurselevel}\empty % needed as we use detokenize (ok, we can
-        \letregisterparameter{\c!keys   :\recurselevel}\empty % avoid it, but it's faster too)
+        \resetregisterparameter{\c!entries:\recurselevel}% needed as we use detokenize (ok, we can
+        \resetregisterparameter{\c!keys   :\recurselevel}% avoid it, but it's faster too)
       }%
       %
       \setfalse\c_strc_registers_defining
@@ -202,8 +202,8 @@
 
 %D Registering:
 
-\glet\currentregistername  \empty
-\glet\currentregisternumber\!!zerocount
+\glettonothing\currentregistername
+\glet         \currentregisternumber\!!zerocount
 
 \def\strc_registers_register_page_entry
   {\iftrialtypesetting
@@ -1083,7 +1083,7 @@
      \fi
    \fi}
 
-\let\m_current_register\empty
+\lettonothing\m_current_register
 
 \permanent\protected\def\pushcurrentregister#1%
   {\let\m_current_register\currentregister
@@ -1156,7 +1156,7 @@
        \doapplyregisterentrycommand{#2}{#5}%
      \fi
    \else
-     \let\currentregisterseeindex\empty
+     \lettonothing\currentregisterseeindex
      \doapplyregisterentrycommand{#2}{#5}%
    \fi
    \popcurrentregister}
@@ -1191,7 +1191,7 @@
    \iflocation
      \def\currentregisterseeindex{#6}%
    \else
-     \let\currentregisterseeindex\empty
+     \lettonothing\currentregisterseeindex
    \fi
    \ifnum#2=\plusone
      \labeltexts\v!see{\doapplyregisterseecommand{#4}{#7}}%
@@ -1224,7 +1224,7 @@
    \iflocation
      \def\currentregistersectionindex{#6}%
    \else
-     \let\currentregistersectionindex\empty
+     \lettonothing\currentregistersectionindex
    \fi
    \ifnum#2=\plusone\else
       ,\space
@@ -1284,7 +1284,7 @@
 
 % not yet ok : new internal handler names
 
-\aliased\let\registerpageseparatorsymbol\empty
+\lettonothing\registerpageseparatorsymbol
 
 \permanent\protected\def\registerpagebuttonsymbol
   {\vrule\s!width\emwidth\s!height\exheight\s!depth\zeropoint\relax}
@@ -1298,7 +1298,7 @@
   {\enforced\frozen\def\registerpageseparatorsymbol{,\space}} % now done via conversion
 
 \defcsname\??registersymbol\v!none\endcsname
-  {\enforced\frozen\let\registerpageseparatorsymbol\empty
+  {\enforced\frozen\lettonothing\registerpageseparatorsymbol
    \enforced\frozen\let\registeronepage\gobblefivearguments
    \enforced\frozen\let\registerpagerange\gobbleeightarguments}
 
diff --git a/tex/context/base/mkxl/strc-ren.mkxl b/tex/context/base/mkxl/strc-ren.mkxl
index 012722f6e..1c9c23ac0 100644
--- a/tex/context/base/mkxl/strc-ren.mkxl
+++ b/tex/context/base/mkxl/strc-ren.mkxl
@@ -435,9 +435,10 @@
    \c!renderingsetup=\??headrenderings:\currentheadalternative]
 
 \let\currentheadalternative         \v!normal
-\let\currentheadrenderingsetup      \empty
 \let\currentheadrenderingalternative\v!vertical
 
+\lettonothing\currentheadrenderingsetup
+
 \permanent\tolerant\protected\def\defineheadplacement[#1]#*[#2]%
   {\doifelsenextbgroup
      {\strc_rendering_define_placement_yes[#1][#2]}%
@@ -465,8 +466,8 @@
 % \headshownumber
 % \headisdisplay
 
-\let\headnumbercontent\empty
-\let\headtextcontent  \empty
+\lettonothing\headnumbercontent
+\lettonothing\headtextcontent
 
 \newdimen\headwidth
 \newdimen\headtextwidth
diff --git a/tex/context/base/mkxl/strc-sbe.mkxl b/tex/context/base/mkxl/strc-sbe.mkxl
index f301583ec..5ece81a43 100644
--- a/tex/context/base/mkxl/strc-sbe.mkxl
+++ b/tex/context/base/mkxl/strc-sbe.mkxl
@@ -79,7 +79,7 @@
       bookmark {\sectionblockparameter\c!bookmark}%
    \relax}
 
-\mutable\let\currentsectionblock\empty % was \s!unknown
+\mutable\lettonothing\currentsectionblock % was \s!unknown
 
 \permanent\tolerant\protected\def\startsectionblock[#1]#*[#2]%
   {%\ctxlua{structures.counters.check(0)}% we assume sane usage of \page, as this is the only workable place (in push)
diff --git a/tex/context/base/mkxl/strc-sec.mkxl b/tex/context/base/mkxl/strc-sec.mkxl
index 3973d0834..9ac35ee15 100644
--- a/tex/context/base/mkxl/strc-sec.mkxl
+++ b/tex/context/base/mkxl/strc-sec.mkxl
@@ -55,8 +55,8 @@
 \def\m_strc_references_prefix_yes{+}
 \def\m_strc_references_prefix_nop{-}
 
-\mutable\let\currentstructurereferenceprefix\empty
-\mutable\let\currentstructurereferencetext  \empty
+\mutable\lettonothing\currentstructurereferenceprefix
+\mutable\lettonothing\currentstructurereferencetext
 
 \installglobalmacrostack\currentstructurereferenceprefix
 
@@ -105,15 +105,16 @@
 \permanent\def\namedstructureheadlocation#1% expandable, maybe [#1]
   {\csname\??savedinternalreference\ifcsname\??savedinternalreference#1\endcsname#1\else\s!default\fi\endcsname}
 
-\mutable\let\currentheadbackreference       \empty
-\mutable\let\currentheaddefault             \empty
-\mutable\let\currentheadincrement           \empty
-\mutable\let\currentheadinteraction         \empty
-\mutable\let\currentheadlabeltag            \empty
-\mutable\let\currentheadnumber              \!!zerocount
-\mutable\let\currentheadrenderingalternative\empty
-\mutable\let\currentheadrenderingsetup      \empty
-\mutable\let\currentheadtext                \empty
+\mutable\lettonothing\currentheadbackreference
+\mutable\lettonothing\currentheaddefault
+\mutable\lettonothing\currentheadincrement
+\mutable\lettonothing\currentheadinteraction
+\mutable\lettonothing\currentheadlabeltag
+\mutable\lettonothing\currentheadrenderingalternative
+\mutable\lettonothing\currentheadrenderingsetup
+\mutable\lettonothing\currentheadtext
+
+\mutable\let\currentheadnumber\!!zerocount
 
 % zeros:
 %
@@ -457,9 +458,9 @@
    \setstructurelevel\currenthead{\thenamedheadlevel\currenthead}%
 \to \everyredefinehead
 
-\mutable\let\currentsectionheadcoupling\empty
-\mutable\let\currentsectionheadsection \empty
-\mutable\let\currentsectionlevel       \empty
+\mutable\lettonothing\currentsectionheadcoupling
+\mutable\lettonothing\currentsectionheadsection
+\mutable\lettonothing\currentsectionlevel
 
 \appendtoks
     % beware, this is a global register
@@ -502,14 +503,14 @@
    \pop_macro_currentheadparent
    \pop_macro_currenthead}
 
-\mutable\let\currentnamedsection\empty
+\mutable\lettonothing\currentnamedsection
 
 \installmacrostack\currentnamedsection
 
 % structure sections (the parents of chapter etc)
 
-\aliased\let\firstsectionname\empty
-\aliased\let\lastsectionname \empty
+\mutable\lettonothing\firstsectionname
+\mutable\lettonothing\lastsectionname
 
 %aliased\let\resetallstructuremarks            \relax
 %aliased\let\resetcurrentstructuremarks        \relax
@@ -554,7 +555,7 @@
 
 \newtoks\everydefinesection
 
-\mutable\let\currentsection\empty % historic alias
+\mutable\lettonothing\currentsection % historic alias
 
 \permanent\protected\def\definesection[#1]%
   {\ifcsname\??headlevel#1\endcsname \else
@@ -819,9 +820,10 @@
    \fi
    \dostoptagged}
 
-\mutable\let\currenthead        \empty
-\mutable\let\currentheadcoupling\empty
-\mutable\let\currentheadsection \empty
+\mutable\lettonothing\currenthead
+\mutable\lettonothing\currentheadcoupling
+\mutable\lettonothing\currentheadsection
+
 \mutable\let\currentheadlevel   \!!zerocount
 \mutable\let\currentheadcounter \!!zerocount
 
@@ -876,9 +878,9 @@
 \newtoks\everybeforesectionheadhandle
 \newtoks\everyaftersectionheadhandle
 
-\mutable\let\getheadnumber\empty
-\mutable\let\getheadtitle \empty
-\mutable\let\getheadsyncs \empty
+\mutable\lettonothing\getheadnumber
+\mutable\lettonothing\getheadtitle
+\mutable\lettonothing\getheadsyncs
 
 \def\strc_sectioning_handle#1#2#3% name data userdata (we can move #1 to the caller)
   {\xdef\currenthead        {#1}%
@@ -905,9 +907,9 @@
    %
    % \currentstructuresynchronize % will move
    %
-   \let\getheadnumber\empty
-   \let\getheadtitle \empty
-   \let\getheadsyncs \empty
+   \lettonothing\getheadnumber
+   \lettonothing\getheadtitle
+   \lettonothing\getheadsyncs
    \ifconditional\c_strc_sectioning_increment
      \ifconditional\c_strc_sectioning_place
        \strc_sectioning_before_yes
@@ -1214,7 +1216,7 @@
 %permanent\def\previoussectioncountervalue{\clf_depthnumber\numexpr\thenamedheadlevel\currenthead+\minusone\relax}
 \permanent\def\previoussectioncountervalue{\clf_depthnumber\numexpr\thenamedheadlevel\previoushead\relax}
 
-\mutable\let\previoushead\empty
+\mutable\lettonothing\previoushead
 
 \def\strc_sectioning_handle_page_nop
   {\edef\p_continue{\headparameter\c!continue}%
diff --git a/tex/context/base/mkxl/strc-syn.mkxl b/tex/context/base/mkxl/strc-syn.mkxl
index e6081d0d9..af6d0c6e2 100644
--- a/tex/context/base/mkxl/strc-syn.mkxl
+++ b/tex/context/base/mkxl/strc-syn.mkxl
@@ -260,12 +260,12 @@
 
 % these  might become private
 
-\mutable\let\currentsynonymoption   \empty
-\mutable\let\currentsynonymcoding   \empty
-\mutable\let\currentsynonymexpansion\empty
-\mutable\let\currentsynonym         \empty
-\mutable\let\currentsynonymtag      \empty
-\mutable\let\currentsynonymtext     \empty
+\mutable\lettonothing\currentsynonymoption
+\mutable\lettonothing\currentsynonymcoding
+\mutable\lettonothing\currentsynonymexpansion
+\mutable\lettonothing\currentsynonym
+\mutable\lettonothing\currentsynonymtag
+\mutable\lettonothing\currentsynonymtext
 
 \permanent\tolerant\protected\def\definesynonyms[#1]#*[#2]#*[#3]#*[#4]% name plural \meaning \use
   {\ifnum\lastarguments=\plusfour
@@ -498,7 +498,7 @@
      {}% todo: message that invalid
    \endgroup}
 
-\mutable\let\currentsimplelistentry\empty
+\mutable\lettonothing\currentsimplelistentry
 
 \protected\def\strc_synonym_normal#1#2#3#4%
   {\begingroup
@@ -527,12 +527,12 @@
 
 % these  might become private
 
-\mutable\let\currentsortingoption   \empty
-\mutable\let\currentsortingcoding   \empty
-\mutable\let\currentsortingexpansion\empty
-\mutable\let\currentsorting         \empty
-\mutable\let\currentsortingtag      \empty
-\mutable\let\currentsortingtext     \empty
+\mutable\lettonothing\currentsortingoption
+\mutable\lettonothing\currentsortingcoding
+\mutable\lettonothing\currentsortingexpansion
+\mutable\lettonothing\currentsorting
+\mutable\lettonothing\currentsortingtag
+\mutable\lettonothing\currentsortingtext
 
 \permanent\tolerant\protected\def\definesorting[#1]#*[#2]#*[#3]%
   {\ifnum\lastarguments=\plusthree
diff --git a/tex/context/base/mkxl/strc-tag.mkxl b/tex/context/base/mkxl/strc-tag.mkxl
index 55f8125f8..3c00acb65 100644
--- a/tex/context/base/mkxl/strc-tag.mkxl
+++ b/tex/context/base/mkxl/strc-tag.mkxl
@@ -280,7 +280,7 @@
 
 \newconditional\c_strc_tags_enabled
 
-\aliased\let\dotaggedplaceholder\empty
+\lettonothing\dotaggedplaceholder
 
 \immutable\chardef\strc_tags_placeholder_char\zerocount % "FFFC
 
@@ -309,7 +309,7 @@
      \enforced\let\dostoptagged         \donothing
    \else
      % initial
-     \enforced\let\dotaggedplaceholder  \empty
+     \enforced\lettonothing\dotaggedplaceholder
      \enforced\let\dostarttagged        \gobbletwoarguments
      \enforced\let\dostarttaggednodetail\gobbleoneargument
      \enforced\let\dostarttaggedchained \gobblethreearguments
@@ -388,10 +388,10 @@
   {\endgraf % we end before the group
    \begingroup
    \ifarguments
-     \let\currentparagraph\empty
+     \lettonothing\currentparagraph
    \or
      \ifhastok={#1}%
-       \let\currentparagraph\empty
+       \lettonothing\currentparagraph
        \setupcurrentparagraph[#1]
      \else
        \edef\currentparagraph{#1}%
diff --git a/tex/context/base/mkxl/strc-usr.mkxl b/tex/context/base/mkxl/strc-usr.mkxl
index 9ecb80ebd..cd1f97dec 100644
--- a/tex/context/base/mkxl/strc-usr.mkxl
+++ b/tex/context/base/mkxl/strc-usr.mkxl
@@ -98,7 +98,7 @@
 
 \permanent\protected\def\startuserdata
   {\begingroup
-   \let\currentuserdata\empty
+   \lettonothing\currentuserdata
    \doifelsenextoptionalcs\userdata_start_delayed\userdata_start_indeed}
 
 \def\userdata_start_delayed[#1]%
diff --git a/tex/context/base/mkxl/supp-box.mkxl b/tex/context/base/mkxl/supp-box.mkxl
index 5a45396d1..cc934fe04 100644
--- a/tex/context/base/mkxl/supp-box.mkxl
+++ b/tex/context/base/mkxl/supp-box.mkxl
@@ -1081,7 +1081,7 @@
 
 %D This can be done in a more modern way but for nostalgic reasons we keep it.
 
-\mutable\let\nextprocessedtoken\empty
+\mutable\lettonothing\nextprocessedtoken
 
 \mutable\let\before \relax % for now mutable
 %mutable\let\between\relax % is a math character
@@ -1180,8 +1180,8 @@
 
 %D See \MKIV\ file for the older implementation.
 
-\let\m_syst_boxes_left \empty
-\let\m_syst_boxes_right\empty
+\lettonothing\m_syst_boxes_left
+\lettonothing\m_syst_boxes_right
 
 \permanent\protected\def\limitatetext#1#2#3%
   {% we could also split in \LUA
diff --git a/tex/context/base/mkxl/symb-ini.mkxl b/tex/context/base/mkxl/symb-ini.mkxl
index e26892e4d..cf61ddb1f 100644
--- a/tex/context/base/mkxl/symb-ini.mkxl
+++ b/tex/context/base/mkxl/symb-ini.mkxl
@@ -58,12 +58,12 @@
 \setupsymbols
   [\c!stylealternative=\v!text]
 
-\mutable\let\currentsymbol   \empty
-\mutable\let\currentsymbolset\empty
+\mutable\lettonothing\currentsymbol
+\mutable\lettonothing\currentsymbolset
 
 \newtoks\t_symb_setups
 
-\let\m_symb_current_set\empty
+\lettonothing\m_symb_current_set
 
 \newconditional\c_symb_found
 
@@ -88,7 +88,7 @@
 \aliased\let\doifinsymbolsetelse\doifelseinsymbolset
 \aliased\let\doifsymbolsetelse  \doifelsesymbolset
 
-\letvalue{\??symbolset}\empty
+\letvalue\??symbolset\empty
 
 %def\symbolset#1{\csname\??symbolset\ifcsname\??symbolset#1\endcsname#1\fi\endcsname} % no [#1], to be used in commalists etc
 
diff --git a/tex/context/base/mkxl/syst-aux.mkxl b/tex/context/base/mkxl/syst-aux.mkxl
index a507218c1..410d959bf 100644
--- a/tex/context/base/mkxl/syst-aux.mkxl
+++ b/tex/context/base/mkxl/syst-aux.mkxl
@@ -163,7 +163,7 @@
 %D alternatives to this command. Beware, only the simple one has \type {\noexpand}
 %D before its argument.
 
-\let\m_syst_helpers_expanded\empty
+\lettonothing\m_syst_helpers_expanded
 
 \pushoverloadmode
 
@@ -224,17 +224,17 @@
 
 %D Maybe even nicer is a let that aliases but keeps the name.
 
-%          \aliased\let\donothing\empty
+       % \lettonothing\donothing
          \immutable\def\donothing        {} % better in tracing
 %untraced\immutable\def\untraceddonothing{}
 
-\let\m_syst_string_one  \empty
-\let\m_syst_string_two  \empty
-\let\m_syst_string_three\empty
-\let\m_syst_string_four \empty
+\lettonothing\m_syst_string_one
+\lettonothing\m_syst_string_two
+\lettonothing\m_syst_string_three
+\lettonothing\m_syst_string_four
 
-\let\m_syst_action_yes  \empty
-\let\m_syst_action_nop  \empty
+\lettonothing\m_syst_action_yes
+\lettonothing\m_syst_action_nop
 
 %D \macros
 %D   {doifnextcharelse}
@@ -806,7 +806,7 @@
 %D arguments state. Again it permits leaner and meaner macro definitions with a bit
 %D less clutter in tracing.
 
-\mutable\let\commalistcommand\empty
+\mutable\lettonothing\commalistcommand
 
 \protected\def\syst_helpers_process_comma_item#+,%
   {\ifarguments
@@ -931,7 +931,7 @@
 
 \let\syst_helpers_comma_list_step\relax
 
-\mutable\let\currentcommalistitem\empty
+\mutable\lettonothing\currentcommalistitem
 
 \permanent\protected\def\startprocesscommalist[#1]#2\stopprocesscommalist
   {\def\syst_helpers_comma_list_step##1{\def\currentcommalistitem{##1}#2}%
@@ -987,17 +987,17 @@
 %D this more hip and a bit faster now but \unknown\ it's seldom used nowadays as we
 %D have better ways now.
 
-\mutable\let\commalistelement\empty
+\mutable\lettonothing\commalistelement
 
-\let\m_syst_string_one\empty
-\let\m_syst_string_two\empty
+\lettonothing\m_syst_string_one
+\lettonothing\m_syst_string_two
 
 \let\syst_helpers_do_compare_process_action\relax
 
 \protected\def\syst_helpers_do_compare_process_action_a[#1=>#2][#3]%
   {\edef\m_syst_string_two{#1}%
    \ifx\m_syst_string_two\s!default
-     \let\commalistelement\empty
+     \lettonothing\commalistelement
      #2%
    \fi}
 
@@ -1115,8 +1115,8 @@
 %D A two step expansion is used to prevent problems with complicated arguments, for
 %D instance arguments that consist of two or more expandable tokens.
 
-\mutable\let\firstcharacter     \empty
-\mutable\let\remainingcharacters\empty
+\mutable\lettonothing\firstcharacter
+\mutable\lettonothing\remainingcharacters
 
 \permanent\protected\def\getfirstcharacter     #1{\clf_getfirstcharacter{#1}}
 \permanent\protected\def\doifelsefirstchar   #1#2{\clf_doifelsefirstchar{#1}{#2}}
@@ -1160,7 +1160,7 @@
 % \let\syst_helpers_do_do_if_in_string     \relax
 % \let\syst_helpers_do_do_if_not_in_string \relax
 %
-% \let\m_syst_sub_string                   \empty
+% \lettonothing\m_syst_sub_string
 %
 % \protected\def\doifelseinstring#1%
 %   {\edef\m_syst_sub_string{#1}% expand #1 here
@@ -1586,7 +1586,7 @@
 %D funny to see that this alternative saw the light so lately --- can be used to do
 %D expanded assigments.
 
-% \mutable\let\currentvalue\empty % only mkii
+% \mutable\lettonothing\currentvalue % only mkii
 
 \permanent\protected\def\getparameters   {\dogetparameters\dosetvalue}
 \permanent\protected\def\geteparameters  {\dogetparameters\dosetevalue}
@@ -1661,8 +1661,9 @@
 %D trouble and tokens.
 
 \mutable\let\currentassignmentlistcommand\gobbletwoarguments
-\mutable\let\currentassignmentlistkey    \empty
-\mutable\let\currentassignmentlistvalue  \empty
+
+\mutable\lettonothing\currentassignmentlistkey
+\mutable\lettonothing\currentassignmentlistvalue
 
 \let\syst_helpers_process_assign_entry\gobbleoneargument
 
@@ -1838,7 +1839,7 @@
   {\expandafterspaces\syst_helpers_get_from_comma_list}
 
 \permanent\protected\def\getfromcommalist[#1]#*[#2]%
-  {\let\commalistelement\empty
+  {\lettonothing\commalistelement
    \commalistcounter#2\relax
    \expandafterspaces\syst_helpers_get_from_comma_list#1\ignorearguments\ignorearguments}
 
@@ -2819,8 +2820,8 @@
 %D
 %D Trivial:
 
-\permanent\protected\def\letempty      #1{\let #1\empty}
-\permanent\protected\def\globalletempty#1{\glet#1\empty}
+\permanent\protected\def\letempty      #1{\lettonothing #1}
+\permanent\protected\def\globalletempty#1{\glettonothing#1}
 
 \permanent\protected\def\letvalueempty #1{\letcsname #1\endcsname\empty}
 \permanent\protected\def\letgvalueempty#1{\gletcsname#1\endcsname\empty}
@@ -3195,7 +3196,8 @@
 \mutable\def\recurselevel{0}
 
 \mutable\let\recurseaction\relax
-\mutable\let\recursestring\empty
+
+\mutable\lettonothing\recursestring
 
 %% \protected\def\syst_helpers_stepwise_recurse#1#2#3% from to step
 %%   {\ifnum#1>#2\relax
@@ -3472,12 +3474,12 @@
 %D Here are the more modern implementations:
 
 \permanent\protected\def\installmacrostack#1%
-  {\ifdefined#1\else\mutable\let#1\empty\fi
+  {\ifdefined#1\else\mutable\lettonothing#1\fi
    \protected\gdefcsname push_macro_\csstring#1\endcsname{\localpushmacro#1}%
    \protected\gdefcsname  pop_macro_\csstring#1\endcsname{\localpopmacro #1}}
 
 \permanent\protected\def\installglobalmacrostack#1%
-  {\ifdefined#1\else\mutable\glet#1\empty\fi
+  {\ifdefined#1\else\mutable\glettonothing#1\fi
    \protected\gdefcsname push_macro_\csstring#1\endcsname{\globalpushmacro#1}%
    \protected\gdefcsname  pop_macro_\csstring#1\endcsname{\globalpopmacro #1}}
 
@@ -4493,7 +4495,8 @@
 %D These macros are clones of the ones implemented in page~378 of Knuth's \TEX book.
 
 \newtoks\t_syst_helpers_scratch
-\let    \m_syst_helpers_scratch\empty
+
+\lettonothing\m_syst_helpers_scratch
 
 \permanent\protected\def\appendtoks#1\to#2%
   {\ifrelax\dodoglobal
@@ -4629,9 +4632,9 @@
 \permanent\protected\def\beforesplitstring#1\at#2\to#3%
   {\def\syst_helpers_split_string##1#2##0^^^^0004% no #- as we need to count
      {\ifarguments
-        \let#3\empty
+        \lettonothing#3%
       \or
-        \let#3\empty
+        \lettonothing#3%
       \else
         \def#3{##1}%
      \fi}%
@@ -4640,7 +4643,7 @@
 \permanent\protected\def\aftersplitstring#1\at#2\to#3%
   {\def\syst_helpers_split_string##0#2##2^^^^0004% no #- as we need to count
      {\ifarguments
-        \let#3\empty
+        \lettonothing#3%
       \or
         \def#3{#1}%
       \else
@@ -4656,11 +4659,11 @@
 \permanent\protected\def\splitstring#1\at#2\to#3\and#4%
   {\def\syst_helpers_split_string##1#2##2^^^^0004%
      {\ifarguments
-        \let#3\empty
-        \let#4\empty
+        \lettonothing#3*
+        \lettonothing#4*
       \or
         \def#3{#1}%
-        \let#4\empty
+        \lettonothing#4%
       \else
         \def#3{##1}%
         \def#4{##2}%
@@ -4670,11 +4673,11 @@
 \permanent\protected\def\greedysplitstring#1\at#2\to#3\and#4%
   {\def\syst_helpers_split_string##1#2##2^^^^0004%
      {\ifarguments
-        \let#3\empty
-        \let#4\empty
+        \lettonothing#3%
+        \lettonothing#4%
       \or
         \def#3{#1}%
-        \let#4\empty
+        \lettonothing#4%
       \else
         \def#3{##1}%
         \def#4{##2}%
@@ -4700,9 +4703,9 @@
 \permanent\protected\def\aftertestandsplitstring#1\at#2\to#3%
   {\def\syst_helpers_split_string##0#2##2^^^^0004% no #- as we need to count
      {\ifarguments
-        \let#3\empty
+        \lettonothing#3%
       \or
-        \let#3\empty
+        \lettonothing#3%
       \else
         \def#3{##2}%
      \fi}%
@@ -4711,11 +4714,11 @@
 \permanent\protected\def\testandsplitstring#1\at#2\to#3\and#4%
   {\def\syst_helpers_split_string##1#2##2^^^^0004%
      {\ifarguments
-        \let#3\empty
-        \let#4\empty
+        \lettonothing#3%
+        \lettonothing#4%
       \or
-        \let#3\empty
-        \let#4\empty
+        \lettonothing#3%
+        \lettonothing#4%
       \else
         \def#3{##1}%
         \def#4{##2}%
@@ -4876,7 +4879,7 @@
 \permanent\protected\def\substituteincommalist#1#2#3% old, new, list (slooow)
   {\edef\m_syst_string_one{#1}%
    \edef\m_syst_string_two{#2}%
-   \let\m_syst_string_four\empty
+   \lettonothing\m_syst_string_four
    \normalexpanded{\rawprocesscommacommand[#3]}\syst_helpers_substitute_in_comma_list_step
    \let#3\m_syst_string_four}
 
@@ -4903,9 +4906,10 @@
 %D This macro was used in the bibtex code (and is probably no longer needed).
 
 \newcount\c_syst_helpers_comma_list_index
-\let     \m_syst_helpers_comma_list_target\empty
 
-\mutable\let\newcommalistelement\empty
+\lettonothing\m_syst_helpers_comma_list_target
+
+\mutable\lettonothing\newcommalistelement
 
 \def\syst_helpers_replace_in_comma_list_step#1% we can use #+ here too
   {\ifnum\commalistcounter=\c_syst_helpers_comma_list_index\relax
@@ -4938,8 +4942,8 @@
 
 \permanent\protected\def\replaceincommalist#1#2% #1 = commalistelement #2 = position starts at 1
   {\c_syst_helpers_comma_list_index#2\relax
-   \let\m_syst_helpers_comma_list_target\empty
-   \let\commalistelement\empty
+   \lettonothing\m_syst_helpers_comma_list_target
+   \lettonothing\commalistelement
    \commalistcounter\plusone
    \expandafter\processcommalist\expandafter[#1]\syst_helpers_replace_in_comma_list_step
    \dodoglobal\let#1\m_syst_helpers_comma_list_target}
@@ -4952,7 +4956,7 @@
 %D kind of useless for handling comma lists in alignments. In these situations the
 %D next macro can be of use.
 
-\let\m_syst_helpers_comma_list_command_global\empty
+\lettonothing\m_syst_helpers_comma_list_command_global
 
 \def\syst_helpers_comma_list_command_global_step#1,%
   {\if]#1\else
@@ -5361,14 +5365,15 @@
 %D As we can see below, spaces following a control sequence are to enclosed in \type
 %D {{}}.
 
-\let\syst_helpers_strip_character  \relax
-\let\m_syst_helpers_strip_character\empty
+\let\syst_helpers_strip_character\relax
+
+\lettonothing\m_syst_helpers_strip_character
 
 \permanent\protected\def\stripcharacter#1\from#2\to#3%
   {\def\syst_helpers_strip_character##1#1##2\end
      {\edef\m_syst_helpers_strip_character{\m_syst_helpers_strip_character##1}%
       \doifnotempty{##2}{\syst_helpers_strip_character##2\end}}%
-   \let\m_syst_helpers_strip_character\empty
+   \lettonothing\m_syst_helpers_strip_character
    \edef\m_syst_string_one{#2}%
    \expandafter\syst_helpers_strip_character\m_syst_string_one#1\end
    \dodoglobal\let#3\m_syst_helpers_strip_character}
@@ -5599,7 +5604,7 @@
 %D
 %D They remove braces and backslashes and give us something to sort.
 
-\let\m_syst_helpers_untexed\empty
+\lettonothing\m_syst_helpers_untexed
 
 \permanent\protected\def\untexsomething
   {\begingroup
@@ -5785,7 +5790,7 @@
           \advance\privatescratchcounter \minusone
           \edef#3{#3##1}%
         \fi}%
-   % \let#3\empty % #3 can be #2, so:
+   % \lettonothing#3% #3 can be #2, so:
      \expandafter\let\expandafter#3\expandafter\empty
      \expandafter\handletokens#2\with\syst_helpers_split_off_tokens
    \else
@@ -5821,7 +5826,7 @@
 %D assignment, this time by using \type {\futurelet}, and grabbing an argument as
 %D well. That way we can handle the sentinal, a blank space and grouped tokens.
 
-\mutable\let\nexthandledtoken\empty % part of public interface
+\mutable\lettonothing\nexthandledtoken % part of public interface
 
 \let\syst_helpers_handle_tokens_command\relax
 
@@ -6051,13 +6056,13 @@
 
 \let\syst_helpers_serialize_comma_list_step\relax
 
-\mutable\let\serializedcommalist\empty
+\mutable\lettonothing\serializedcommalist
 
 \def\syst_helpers_serialize_comma_list_step#1%
   {\edef\serializedcommalist{\serializedcommalist#1}}
 
 \permanent\protected\def\serializecommalist[#1]%
-  {\let\serializedcommalist\empty
+  {\lettonothing\serializedcommalist
    \processcommacommand[#1]\syst_helpers_serialize_comma_list_step}
 
 %D \macros
@@ -6647,18 +6652,32 @@
    \or      \plusten
    \else    {\number#1}\fi}
 
-\permanent\def\constantdimen#1%
-  {\ifdim#1=\zeropoint
+% \permanent\def\constantdimen#1% takes register
+%   {\ifdim#1=\zeropoint
+%      \zeropoint
+%    \else
+%      \the#1\relax
+%    \fi}
+
+\permanent\def\constantdimen#1% takes register
+  {\ifzeropt#1\norelax
      \zeropoint
    \else
-     \the#1\relax
+     \todimension#1\norelax
    \fi}
 
+% \permanent\def\constantdimenargument#1% takes register
+%   {\ifdim#1=\zeropoint
+%      \zeropoint
+%    \else
+%      {\the#1}%
+%    \fi}
+
 \permanent\def\constantdimenargument#1%
-  {\ifdim#1=\zeropoint
+  {\ifzeropt#1%\norelax
      \zeropoint
    \else
-     {\the#1}%
+     {\todimension#1}%
    \fi}
 
 \permanent\def\constantemptyargument#1%
diff --git a/tex/context/base/mkxl/syst-ini.mkxl b/tex/context/base/mkxl/syst-ini.mkxl
index 96bdde764..b529c04bc 100644
--- a/tex/context/base/mkxl/syst-ini.mkxl
+++ b/tex/context/base/mkxl/syst-ini.mkxl
@@ -494,11 +494,11 @@
 %D \macros
 %D   {tempstring, scratchstring*}
 
-\mutable\let\tempstring      \empty
+\mutable\lettonothing\tempstring
 
-\mutable\let\scratchstring   \empty
-\mutable\let\scratchstringone\empty
-\mutable\let\scratchstringtwo\empty
+\mutable\lettonothing\scratchstring
+\mutable\lettonothing\scratchstringone
+\mutable\lettonothing\scratchstringtwo
 
 %D \macros
 %D   {scratchwidth, scratchheight, scratchdepth, scratchoffset, scratchdistance}
@@ -968,7 +968,7 @@
 %D {\let} (the only advantage is that we often give them names with some
 %D prefix.
 
-\permanent\protected\def\newmacro   #1{\mutable\let#1\empty}
+\permanent\protected\def\newmacro   #1{\mutable\lettonothing#1}
 \permanent\protected\def\setnewmacro#1{\mutable\let#1}
 
 \permanent\protected\def\newfraction#1{\mutable\let#1\!!plusone}
@@ -1234,7 +1234,7 @@
      \immediate\write\statuswrite{fatal error: duplicate system namespace '#1'}%
    \else
      \global\advance\c_syst_helpers_n_of_namespaces\plusone
-     \immutable\edefcsname ??#1\endcsname{\v_interfaces_prefix_template_system}%
+     \immutable\cdefcsname ??#1\endcsname{\v_interfaces_prefix_template_system}%
    \fi}
 
 %D It makes more sense to have these here:
@@ -1281,8 +1281,9 @@
 \mutable\let\of  \relax % \empty
 \mutable\let\and \relax % \empty
 \mutable\let\with\relax % \empty
-\mutable\let\nop \empty % used often
-\mutable\let\yes \empty % used often
+
+\mutable\lettonothing\nop % used often
+\mutable\lettonothing\yes % used often
 
 %D Another experiment:
 
diff --git a/tex/context/base/mkxl/tabl-frm.mkxl b/tex/context/base/mkxl/tabl-frm.mkxl
index 4caa287f7..d3112d9c2 100644
--- a/tex/context/base/mkxl/tabl-frm.mkxl
+++ b/tex/context/base/mkxl/tabl-frm.mkxl
@@ -102,13 +102,13 @@
      \setupframed[\??framedtablecolumn#1:#2][#3]%
    \fi}
 
-\mutable\let\currentframedtable\empty
+\mutable\lettonothing\currentframedtable
 
 \permanent\tolerant\protected\def\startframedtable[#1]#*[#2]%
   {\begingroup
    \forgetall
    \ifhastok={#1}%
-     \let\currentframedtable\empty
+     \lettonothing\currentframedtable
      \setupframed[\??framedtable][#1]%
    \else
      \edef\currentframedtable{#1}%
@@ -218,7 +218,7 @@
       \fi}%
    \ifcase\c_tabl_framed_pass
    \or
-     \letframedparameter\c!background\empty
+     \resetframedparameter\c!background
      \letframedparameter\c!frame\v!off
    \or
      \letframedparameter\c!height\d_tabl_framed_h
diff --git a/tex/context/base/mkxl/tabl-ltb.mkxl b/tex/context/base/mkxl/tabl-ltb.mkxl
index 3376b30c6..54bce7d94 100644
--- a/tex/context/base/mkxl/tabl-ltb.mkxl
+++ b/tex/context/base/mkxl/tabl-ltb.mkxl
@@ -140,7 +140,8 @@
 \permanent\def\linetablerparameter#1% faster, leaner and meaner
   {\begincsname
      \??linetable
-     \ifnum\c_tabl_lines_row=\zerocount % geen ifcase
+   % \ifnum\c_tabl_lines_row=\zerocount % geen ifcase
+     \ifzero\c_tabl_lines_row
        \ifcsname\??linetable r:\v!header#1\endcsname
          r:\v!header
        \orelse\ifcsname\??linetable r:0#1\endcsname
@@ -348,7 +349,7 @@
           \dp\b_tabl_lines_current\c_tabl_lines_part\strutdepth
           % noindent en endgraf needed else whitespace mess-up!
           \whitespace % here not after verticalstrut
-          \ifdim\topskipgap=\zeropoint\else
+          \ifzeropt\topskipgap\else
             \verticalstrut
             \nobreak
             \kern-\struttotal
diff --git a/tex/context/base/mkxl/tabl-ntb.mkxl b/tex/context/base/mkxl/tabl-ntb.mkxl
index dc644270d..59777fb9b 100644
--- a/tex/context/base/mkxl/tabl-ntb.mkxl
+++ b/tex/context/base/mkxl/tabl-ntb.mkxl
@@ -213,7 +213,7 @@
 \let\tabl_ntb_anchor_stop   \relax
 \let\tabl_ntb_anchor_process\gobbleoneargument
 
-\let\m_tabl_ntb_anchor_background\empty
+\lettonothing\m_tabl_ntb_anchor_background
 
 \let\xanchor\!!zerocount
 \let\yanchor\!!zerocount
@@ -239,17 +239,17 @@
 
 \def\tabl_ntb_anchor_setup
   {\ifcstok{\naturaltablelocalparameter\c!synchronize}\v!background
-     \let\tabl_ntb_anchor_start   \tabl_ntb_anchor_start_indeed
-     \let\tabl_ntb_anchor_stop    \tabl_ntb_anchor_stop_indeed
-     \let\tabl_ntb_anchor_process \tabl_ntb_anchor_process_indeed
+     \let\tabl_ntb_anchor_start\tabl_ntb_anchor_start_indeed
+     \let\tabl_ntb_anchor_stop\tabl_ntb_anchor_stop_indeed
+     \let\tabl_ntb_anchor_process\tabl_ntb_anchor_process_indeed
      \edef\m_tabl_ntb_anchor_background{\naturaltablelocalparameter\c!background}%
      \resetnaturaltablelocalparameter\c!background
      \setlocalanchoring
    \else
-     \let\m_tabl_ntb_anchor_background\empty
-     \let\tabl_ntb_anchor_start       \gobbletwoarguments
-     \let\tabl_ntb_anchor_stop        \relax
-     \let\tabl_ntb_anchor_process     \gobbleoneargument
+     \lettonothing\m_tabl_ntb_anchor_background
+     \let\tabl_ntb_anchor_start\gobbletwoarguments
+     \let\tabl_ntb_anchor_stop\relax
+     \let\tabl_ntb_anchor_process\gobbleoneargument
    \fi
    \resetnaturaltablelocalparameter\c!synchronize}
 
@@ -721,9 +721,9 @@
 % \dorecurse{10}{\bTR \dorecurse{6}{\bTD xxx \eTD} \eTR}
 % \eTABLE
 
-\let\m_tabl_ntb_before_split\empty
-\let\m_tabl_ntb_after_split \empty
-\let\m_tabl_ntb_same_page   \empty
+\lettonothing\m_tabl_ntb_before_split
+\lettonothing\m_tabl_ntb_after_split
+\lettonothing\m_tabl_ntb_same_page
 
 % split + page:
 %
@@ -758,13 +758,13 @@
    \fi[#1]}
 
 \def\tabl_ntb_td_yes[#1]#2\eTD
-  {\letnaturaltableparameter\c!ny    \m_tabl_ntb_default_nr
-   \letnaturaltableparameter\c!nx    \m_tabl_ntb_default_nc
-   \letnaturaltableparameter\c!nc    \plusone
-   \letnaturaltableparameter\c!nr    \plusone
-   \letnaturaltableparameter\c!n     \c_tabl_ntb_running_col
-   \letnaturaltableparameter\c!m     \empty
-   \letnaturaltableparameter\c!action\empty % not that important
+  {\letnaturaltableparameter  \c!ny    \m_tabl_ntb_default_nr
+   \letnaturaltableparameter  \c!nx    \m_tabl_ntb_default_nc
+   \letnaturaltableparameter  \c!nc    \plusone
+   \letnaturaltableparameter  \c!nr    \plusone
+   \letnaturaltableparameter  \c!n     \c_tabl_ntb_running_col
+   \resetnaturaltableparameter\c!m
+   \resetnaturaltableparameter\c!action% not that important
    \setupcurrentnaturaltable[#1]%
    %
    \c_tabl_ntb_nx\naturaltableparameter\c!nx\relax
@@ -850,8 +850,8 @@
    \letnaturaltableparameter\c!nc\plusone
    \letnaturaltableparameter\c!nr\plusone
    \setupcurrentnaturaltable[#1]%
-   \letnaturaltableparameter\c!n \empty
-   \letnaturaltableparameter\c!m \empty}
+   \resetnaturaltableparameter\c!n
+   \resetnaturaltableparameter\c!m}
 
 \def\tabl_ntb_td_pass_m#1%
   {\scratchcounter\numexpr\m_tabl_ntb_m-\c_tabl_ntb_running_col+\minusone-\c_tabl_ntb_spn\relax
@@ -862,8 +862,8 @@
    \letnaturaltableparameter\c!nc\plusone
    \letnaturaltableparameter\c!nr\plusone
    \setupcurrentnaturaltable[#1]%
-   \letnaturaltableparameter\c!n \empty
-   \letnaturaltableparameter\c!m \empty}
+   \resetnaturaltableparameter\c!n
+   \resetnaturaltableparameter\c!m}
 
 \def\tabl_ntb_cell_preset
   {\c_tabl_ntb_current_row\c_tabl_ntb_maximum_row
@@ -1291,9 +1291,9 @@
    \xdef\m_tabl_ntb_same_page   {#3}}
 
 \protected\def\tabl_ntb_row_align_reset
-  {\glet\m_tabl_ntb_before_split\empty
-   \glet\m_tabl_ntb_after_split \empty
-   \glet\m_tabl_ntb_same_page   \empty}
+  {\glettonothing\m_tabl_ntb_before_split
+   \glettonothing\m_tabl_ntb_after_split
+   \glettonothing\m_tabl_ntb_same_page   }
 
 \def\tabl_ntb_prelocate_error
   {\writestatus\m!TABLE{fatal error: use \string\prelocateTBLrows\space to increase table memory (now: \the\c_tabl_prelocated_rows)}}
@@ -1397,7 +1397,7 @@
 
 \protected\def\tabl_ntb_after_page
   {\ifnum\c_tabl_ntb_row>\c_tabl_ntb_n_of_head_lines
-     \ifnum\tabl_ntb_get_nob\c_tabl_ntb_row=\zerocount
+     \ifnum\tabl_ntb_get_nob\c_tabl_ntb_row=\zerocount % no \ifzero
        \ifx\m_tabl_ntb_same_page\v!after
        % \blank[\v!samepage,\v!strong]%
          \nobreak
@@ -1632,9 +1632,9 @@
 \def\tabl_ntb_table_stop
   {\forgetall % new, here see narrower-004.tex
   %\setbox\scratchbox\hbox
-  %  {\letnaturaltablelocalparameter\c!frame\v!off
-  %   \letnaturaltablelocalparameter\c!background\empty
-  %   \letnaturaltablelocalparameter\c!align\v!no
+  %  {\letnaturaltablelocalparameter  \c!frame     \v!off
+  %   \resetnaturaltablelocalparameter\c!background
+  %   \letnaturaltablelocalparameter  \c!align     \v!no
   %   \inheritednaturaltablelocalframed{\strut}}%
   %\edef\minimalcellheight{\the\ht\scratchbox}% not used
    \localcontrolledloop\plusone\c_tabl_ntb_maximum_col\plusone
@@ -2010,10 +2010,10 @@
 
 \protected\def\tabl_ntb_cell_process_a#1#2[#3]#4% grouping added ! ! !
   {\begingroup
-   \letnaturaltablelocalparameter\c!option\empty
+   \resetnaturaltablelocalparameter\c!option\empty
    \tabl_ntb_setup_cell{#1}{#2}%
    \setupcurrentnaturaltablelocal[#3]%
-   \letnaturaltablelocalparameter\c!background\empty
+   \resetnaturaltablelocalparameter\c!background
    \letnaturaltablelocalparameter\c!frame\v!off
    \scratchcounter\tabl_ntb_get_col{#1}{#2}\relax
    \setbox\scratchbox\hbox
@@ -2073,7 +2073,7 @@
    \setbox\scratchbox\hbox
      {\tabl_ntb_setup_cell{#2}{#3}%
       \setupcurrentnaturaltablelocal[#4,#1]%
-      \letnaturaltablelocalparameter\c!background\empty
+      \resetnaturaltablelocalparameter\c!background
       \letnaturaltablelocalparameter\c!frame\v!off
       \inheritednaturaltablelocalframed{\tabl_ntb_cell_start#5\tabl_ntb_cell_stop}}%
    \setbox\scratchboxone\emptyhbox
@@ -2115,9 +2115,9 @@
   {\tabl_ntb_setup_cell{#1}{#2}%
    \bgroup
    \setupcurrentnaturaltablelocal[#3]%
-   \letnaturaltablelocalparameter\c!background\empty
-   \letnaturaltablelocalparameter\c!frame\v!off
-   \setnaturaltablelocalparameter\c!width{\d_tabl_ntb_width}%
+   \resetnaturaltablelocalparameter\c!background
+   \letnaturaltablelocalparameter  \c!frame     \v!off
+   \setnaturaltablelocalparameter  \c!width     {\d_tabl_ntb_width}%
    \inheritednaturaltablelocalframed{\tabl_ntb_cell_start\tabl_ntb_char_align{#1}{#2}#4\tabl_ntb_cell_stop}%
    \egroup}
 
@@ -2126,8 +2126,8 @@
    \tabl_ntb_setup_cell{#1}{#2}%
    \setupcurrentnaturaltablelocal[#3]% to get the color right, the way we
    \directcolor[\naturaltablelocalparameter\c!color]%
-   \letnaturaltablelocalparameter\c!color\empty
-   \setnaturaltablelocalparameter\c!width{\d_tabl_ntb_width}%
+   \resetnaturaltablelocalparameter\c!color
+   \setnaturaltablelocalparameter  \c!width{\d_tabl_ntb_width}%
    \ifzeropt\d_tabl_ntb_height % case: nc=maxcolumns
    \else
      \setnaturaltablelocalparameter\c!height{\d_tabl_ntb_height}%
diff --git a/tex/context/base/mkxl/tabl-tab.mkxl b/tex/context/base/mkxl/tabl-tab.mkxl
index 815767e18..8bd1d052a 100644
--- a/tex/context/base/mkxl/tabl-tab.mkxl
+++ b/tex/context/base/mkxl/tabl-tab.mkxl
@@ -129,7 +129,7 @@
    \!taLastRegularTabskip\scratchskip
    \!taOnceOnlyTabskipfalse
    \!taBeginFormattrue
-   \let\!tfRowOfWidths\empty
+   \lettonothing\!tfRowOfWidths
    \doreadtableformatkeys}
 
 \def\!tfSetWidth
@@ -170,7 +170,7 @@
      \else
        \!tgValue
      \fi
-   \let\!tfWidthText\empty %      Override possible prior `w[sample entry]'
+   \lettonothing\!tfWidthText % Override possible prior `w[sample entry]'
    \doreadtableformatkeys}
 
 \def\!tfSetTabskip
@@ -181,7 +181,7 @@
      \scratchskip\!tgValue
    \fi
    \divide\scratchskip\plustwo
-   \ifnum\!taColumnNumber=\zerocount
+   \ifzero\!taColumnNumber
     %\!thToksEdef\!taRuleColumnTemplate{\the\!taRuleColumnTemplate\tabskip\the\scratchskip}%
      \normalexpanded{\!taRuleColumnTemplate{\the\!taRuleColumnTemplate\tabskip\the\scratchskip}}%
    \else
@@ -221,7 +221,7 @@
    \!tfAdjoinPriorColumn}
 
 \def\!tfAdjoinPriorColumn
-  {\ifnum\!taColumnNumber=\zerocount
+  {\ifzero\!taColumnNumber
      \!taPreamble=\!taRuleColumnTemplate % New \tabskip may have been added
    \else
      \ifempty\!tfRowOfWidths\else  % no "w" keys specified yet, not even this col
@@ -240,7 +240,7 @@
   \!taLeftGlue{\hfil}%
   \!taRightGlue{\hfil}%
   \!taMinimumColumnWidth\zeropoint
-  \let\!tfWidthText\empty
+  \lettonothing\!tfWidthText
   \!taOnceOnlyTabskipfalse
   \doreadtableformatkeys}
 
@@ -325,7 +325,7 @@
 
 \def\!tgCheckForSpace
   {\def\!tgCode{1}%
-   \let\!tgValue\empty
+   \lettonothing\!tgValue
    \ifx\tempstring\!thSpaceToken
      \expandafter\!tgReturn
    \else
@@ -682,7 +682,7 @@
 % extensions
 
 \newtableformatkey q%
-  {\let\!tqStyle\empty
+  {\lettonothing\!tqStyle
    \futurelet\!tnext\!tqTestForBracket}
 
 \newtableformatkey Q%
@@ -759,7 +759,7 @@
    % #2=extra depth
    \!taDimenA=#1\relax
    \!taDimenB=#2\relax
-   \let\!TsSpaceFactor\empty
+   \lettonothing\!TsSpaceFactor
    \ifmmode
      \expandafter\mathpalette % (*) the only place where still use this
      \expandafter\!TsEnlargeMath
@@ -896,8 +896,8 @@
 
 \newcount\c_tabl_table_n_of_vrules \c_tabl_table_n_of_vrules\plusone
 
-\let\m_tabl_table_vrule_color\empty
-\let\m_tabl_table_hrule_color\empty
+\lettonothing\m_tabl_table_vrule_color
+\lettonothing\m_tabl_table_hrule_color
 
 \def\tabl_table_insert_vrule
   {\vrule\s!width
@@ -930,7 +930,7 @@
      \global\c_tabl_table_n_of_vrules\plusone
      \unskip
    \fi
-   \glet\m_tabl_table_vrule_color\empty
+   \glettonothing\m_tabl_table_vrule_color
    \hfil
    \aligntab}
 
@@ -1381,8 +1381,8 @@
   {\tabl_tables_chuck_auto_row % before the tail, else noalign problem
    \tabl_table_insert_tail
    \noalign\bgroup
-     \glet\tabl_table_head\empty
-     \glet\tabl_table_tail\empty
+     \glettonothing\tabl_table_head
+     \glettonothing\tabl_table_tail
    \egroup
    \tabl_table_finish
    \ifempty\p_tabl_table_frame
@@ -1540,7 +1540,7 @@
 
 \newtoks\localtabledefinitions
 
-\mutable\let\currenttableformat\empty
+\mutable\lettonothing\currenttableformat
 
 \def\tabl_table_third_stage#1%
   {\global\settrue\tableactionstatepermitted
@@ -1612,8 +1612,8 @@
    \egroup
    \dontcomplain
    \tabl_table_split_box\tablecontentbox
-   \glet\tabl_table_head\empty % new here
-   \glet\tabl_table_tail\empty % new here
+   \glettonothing\tabl_table_head % new here
+   \glettonothing\tabl_table_tail % new here
    \flushnotes
    \egroup}
 
@@ -1663,8 +1663,8 @@
 
 %D This is so old ... adapting it to use tolerant might break something:
 
-\let\tabl_table_head\empty % needs checking
-\let\tabl_table_tail\empty % needs checking
+\lettonothing\tabl_table_head % needs checking
+\lettonothing\tabl_table_tail % needs checking
 
 \letcsname\e!start\v!tablehead\endcsname\relax % todo: frozen, but we use a grabber
 \letcsname\e!stop \v!tablehead\endcsname\relax % todo: frozen, but we use a grabber
@@ -1711,8 +1711,8 @@
    \noalign\bgroup
      \nobreak
      \tabl_table_set_action\tableunknownstate
-     \glet\tabl_tables_check_auto_row\empty
-     \glet\tabl_tables_chuck_auto_row\empty
+     \glettonothing\tabl_tables_check_auto_row
+     \glettonothing\tabl_tables_chuck_auto_row
      \global\currenttablecolumn\zerocount
    \egroup}
 
@@ -1841,18 +1841,18 @@
   {\glet\tabl_tables_check_auto_row\tabl_tables_check_auto_row_indeed
    \glet\tabl_tables_chuck_auto_row\tabl_tables_chuck_auto_row_indeed}
 
-\let\tabl_tables_check_auto_row\empty
-\let\tabl_tables_chuck_auto_row\empty
+\lettonothing\tabl_tables_check_auto_row
+\lettonothing\tabl_tables_chuck_auto_row
 
 \def\tabl_tables_check_auto_row_indeed
-  {\glet\tabl_tables_check_auto_row\empty
+  {\glettonothing\tabl_tables_check_auto_row
    \ifnum\tableactionstate=\tablerulestate   \FR\orelse
    \ifnum\tableactionstate=\tableunknownstate\FR\else
                                              \MR\fi}
 
 \def\tabl_tables_chuck_auto_row_indeed
-  {\glet\tabl_tables_check_auto_row\empty
-   \glet\tabl_tables_chuck_auto_row\empty
+  {\glettonothing\tabl_tables_check_auto_row
+   \glettonothing\tabl_tables_chuck_auto_row
    \ifnum\tableactionstate=\tablerulestate   \SR\orelse
    \ifnum\tableactionstate=\tableunknownstate\SR\else
                                              \LR\fi}
@@ -1908,8 +1908,8 @@
 \newcount\c_tabl_table_hrule_thickness_factor
 \newcount\c_tabl_table_drule_span
 
-\let\m_tabl_table_vrule_color\empty
-\let\m_tabl_table_hrule_color\empty
+\lettonothing\m_tabl_table_vrule_color
+\lettonothing\m_tabl_table_hrule_color
 
 \appendtoks
     \enforced\let\VL\tabl_table_VL
@@ -1934,7 +1934,7 @@
 \permanent\tolerant\protected\def\tabl_table_VL[#1]%
   {\tabl_tables_check_auto_row
    \global\advance\currenttablecolumn\plusone
-   \glet\m_tabl_table_vrule_color\empty
+   \glettonothing\m_tabl_table_vrule_color
    \global\c_tabl_table_vrule_thickness_factor\m_tabl_table_VLwidth\relax
    \iftok{#1}\emptytoks\else
      \rawprocesscommalist[#1]\tabl_table_vrulecommand
@@ -1978,7 +1978,7 @@
      \bgroup
        \global\c_tabl_table_hrule_thickness_factor\m_tabl_table_HLheight\relax
        \ifparameter#1\or
-         \glet\m_tabl_table_hrule_color\empty
+         \glettonothing\m_tabl_table_hrule_color
          \rawprocesscommalist[#1]\tabl_table_hrulecommand
          \ifempty\m_tabl_table_hrule_color\else
            \switchtocolor[\m_tabl_table_hrule_color]%
@@ -2094,7 +2094,7 @@
      \global\c_tabl_table_hrule_thickness_factor\m_tabl_table_HLheight\relax
      \global\c_tabl_table_drule_span\zerocount
      \iftok{#1}\emptytoks\else
-       \glet\m_tabl_table_hrule_color\empty
+       \glettonothing\m_tabl_table_hrule_color
        \rawprocesscommalist[#1]\tabl_table_drulecommand
      % \ifempty\m_tabl_table_hrule_color\else
      %   \switchtocolor[\m_tabl_table_hrule_color]% see *DL*
diff --git a/tex/context/base/mkxl/tabl-tbl.mkxl b/tex/context/base/mkxl/tabl-tbl.mkxl
index 91ee0262a..ad18daef4 100644
--- a/tex/context/base/mkxl/tabl-tbl.mkxl
+++ b/tex/context/base/mkxl/tabl-tbl.mkxl
@@ -233,7 +233,7 @@
 %newconditional  \c_tabl_pre_is_set
 \newconditional  \c_tabl_post_is_set
 
-\let             \m_tabl_tabulate_separator_factor \empty % fraction
+\lettonothing    \m_tabl_tabulate_separator_factor  % fraction
 
 \aliased\let\tabulatesplitlinemode\c_tabl_tabulate_splitlinemode % temp hack, we need an interface
 
@@ -292,7 +292,7 @@
      \tabl_tabulate_initialize_box_nop#1%
    \fi}
 
-\def\tabl_tabulate_initialize_box_yes  {\global     \setbox\lastnamedcs\emptybox}
+\def\tabl_tabulate_initialize_box_yes  {\global\setbox\lastnamedcs\emptybox}
 \def\tabl_tabulate_initialize_box_nop#1{\expandafter\newbox\csname\??tabulatebox\number#1\endcsname}
 
 \tabl_tabulate_initialize_boxes{16} % not really needed
@@ -361,7 +361,7 @@
      \xdef\m_tabl_tabulate_color{#1}%
    \else
      \glet\m_tabl_tabulate_color\m_tabl_tabulate_color_local
-     \glet\m_tabl_tabulate_color_local\empty
+     \glettonothing\m_tabl_tabulate_color_local
    \fi
    \ifcase\c_tabl_tabulate_localcolorspan
      \global\c_tabl_tabulate_colorspan#2\relax
@@ -388,7 +388,7 @@
      \xdef\m_tabl_tabulate_vrule_color{#1}%
    \else
      \glet\m_tabl_tabulate_vrule_color\m_tabl_tabulate_vrule_color_local
-     \glet\m_tabl_tabulate_vrule_color_local\empty
+     \glettonothing\m_tabl_tabulate_vrule_color_local
    \fi}
 
 \let\tabl_tabulate_check_local_color      \gobbletwoarguments
@@ -408,7 +408,7 @@
 \def\tabl_tabulate_inject_pre_skip#1%
   {\ifdim#1>\zeropoint
      \kern#1\relax % hskip
-   \orelse\ifnum\c_tabl_tabulate_column=\zerocount
+   \orelse\ifzero\c_tabl_tabulate_column
      \ifconditional\c_tabl_tabulate_autorulespacing
        \ifcase\c_tabl_tabulate_has_rule_spec_first\else
          \kern\s_tabl_tabulate_first\relax % hskip
@@ -841,10 +841,10 @@
    \t_tabl_tabulate_emath\emptytoks
    \t_tabl_tabulate_font\emptytoks
    \t_tabl_tabulate_settings\emptytoks
-   \glet\m_tabl_tabulate_alignment\empty
-   \glet\m_tabl_tabulate_color\empty
-   \glet\m_tabl_tabulate_text_color\empty
-   \glet\m_tabl_tabulate_vrule_color\empty
+   \glettonothing\m_tabl_tabulate_alignment
+   \glettonothing\m_tabl_tabulate_color
+   \glettonothing\m_tabl_tabulate_text_color
+   \glettonothing\m_tabl_tabulate_vrule_color
    \global\c_tabl_tabulate_colorspan\zerocount
    \global\setfalse\c_tabl_auto_align_mode
    \global\setfalse\c_tabl_auto_align_mode_new
@@ -871,8 +871,8 @@
    \fi}
 
 \permanent\protected\def\tabl_tabulate_set_last_entry#1% rulespec
-  {\glet\m_tabl_tabulate_color\empty
-   \glet\m_tabl_tabulate_vrule_color\empty
+  {\glettonothing\m_tabl_tabulate_color
+   \glettonothing\m_tabl_tabulate_vrule_color
    \iftok{#1}\emptytoks
      \global\d_tabl_tabulate_vrulethickness\zeropoint
    \else
@@ -1115,9 +1115,9 @@
 
 % Here begins the implementation.
 
-\let\tabl_tabulate_insert_head\empty
-\let\tabl_tabulate_insert_body\empty
-\let\tabl_tabulate_insert_foot\empty
+\lettonothing\tabl_tabulate_insert_head
+\lettonothing\tabl_tabulate_insert_body
+\lettonothing\tabl_tabulate_insert_foot
 
 \def\tabl_tabulate_insert_head_content
   {\noalign{\global\settrue\c_tabl_tabulate_someamble}%
@@ -1134,23 +1134,23 @@
     %\expandafter\ifempty\csname\??tabulatehead\currenttabulation\endcsname
     %\expandafter\ifempty\lastnamedcs
      \ifempty\lastnamedcs
-       \let\tabl_tabulate_insert_head\empty
+       \lettonothing\tabl_tabulate_insert_head
      \else
        \let\tabl_tabulate_insert_head\tabl_tabulate_insert_head_content
      \fi
    \else
-     \let\tabl_tabulate_insert_head\empty
+     \lettonothing\tabl_tabulate_insert_head
    \fi
    \ifcsname\??tabulatefoot\currenttabulation\endcsname
     %\expandafter\ifempty\csname\??tabulatefoot\currenttabulation\endcsname
     %\expandafter\ifempty\lastnamedcs
      \ifempty\lastnamedcs
-       \let\tabl_tabulate_insert_foot\empty
+       \lettonothing\tabl_tabulate_insert_foot
      \else
        \let\tabl_tabulate_insert_foot\tabl_tabulate_insert_foot_content
      \fi
    \else
-     \let\tabl_tabulate_insert_foot\empty
+     \lettonothing\tabl_tabulate_insert_foot
    \fi}
 
 \def\tabl_tabulate_insert_content
@@ -1173,7 +1173,7 @@
 \permanent\protected\defcsname\e!start\v!tabulatehead\endcsname{\doifelsenextoptionalcs\tabl_tabulate_start_head_yes\tabl_tabulate_start_head_nop}
 \permanent\protected\defcsname\e!start\v!tabulatetail\endcsname{\doifelsenextoptionalcs\tabl_tabulate_start_foot_yes\tabl_tabulate_start_foot_nop}
 
-\let\m_tabl_tabulate_data\empty
+\lettonothing\m_tabl_tabulate_data
 
 \def\tabl_tabulate_start_head_yes[#1]%
   {\processcontent{\e!stop\v!tabulatehead}\m_tabl_tabulate_data{\letcsname\??tabulatehead#1\endcsname\m_tabl_tabulate_data}}
@@ -1216,7 +1216,7 @@
 
 \permanent\protected\defcsname\e!start\v!tabulate\endcsname
   {\bgroup % whole thing
-   \let\currenttabulationparent\empty
+   \lettonothing\currenttabulationparent
    \tabl_start_regular}
 
 \tolerant\protected\def\tabl_start_regular[#1]#*[#2]% [format] | [settings] | [format] [settings] | [settings] [format]
@@ -1411,30 +1411,30 @@
 
 % color columns
 
-\let\m_tabl_tabulate_color_previous     \empty
-\let\m_tabl_tabulate_color              \empty
-\let\m_tabl_tabulate_text_color         \empty
-\let\m_tabl_tabulate_color_local        \empty
-\let\m_tabl_tabulate_vrule_color        \empty
-\let\m_tabl_tabulate_vrule_color_local  \empty
-\let\m_tabl_tabulate_vrule_color_default\empty % used local
-\let\m_tabl_tabulate_hrule_color_default\empty % used local
-\let\m_tabl_tabulate_blank_default      \empty
+\lettonothing\m_tabl_tabulate_color_previous
+\lettonothing\m_tabl_tabulate_color
+\lettonothing\m_tabl_tabulate_text_color
+\lettonothing\m_tabl_tabulate_color_local
+\lettonothing\m_tabl_tabulate_vrule_color
+\lettonothing\m_tabl_tabulate_vrule_color_local
+\lettonothing\m_tabl_tabulate_vrule_color_default % used local
+\lettonothing\m_tabl_tabulate_hrule_color_default % used local
+\lettonothing\m_tabl_tabulate_blank_default
 
 \appendtoks
-    \glet  \m_tabl_tabulate_color_previous      \empty
-    \glet  \m_tabl_tabulate_color               \empty
-    \glet  \m_tabl_tabulate_text_color          \empty
-    \glet  \m_tabl_tabulate_color_local         \empty
-    \glet  \m_tabl_tabulate_vrule_color         \empty
-    \glet  \m_tabl_tabulate_vrule_color_local   \empty
+    \glettonothing\m_tabl_tabulate_color_previous
+    \glettonothing\m_tabl_tabulate_color
+    \glettonothing\m_tabl_tabulate_text_color
+    \glettonothing\m_tabl_tabulate_color_local
+    \glettonothing\m_tabl_tabulate_vrule_color
+    \glettonothing\m_tabl_tabulate_vrule_color_local
     \global\d_tabl_tabulate_vrulethickness_local\zeropoint
 \to \t_tabl_tabulate_every_row
 
 \protected\def\tabl_tabulate_color_side_right_second
   {\ifempty\m_tabl_tabulate_color_previous \else
      \tabl_tabulate_color_set\m_tabl_tabulate_color_previous
-     \glet\m_tabl_tabulate_color_previous\empty
+     \glettonothing\m_tabl_tabulate_color_previous
    \fi}
 
 \protected\def\tabl_tabulate_color_side_left_second
@@ -1451,9 +1451,9 @@
   {\ifempty\m_tabl_tabulate_color \else
      \tabl_tabulate_color_set\m_tabl_tabulate_color
      \ifcase\c_tabl_tabulate_colorspan
-       %\glet\m_tabl_tabulate_color_previous\empty
+       %\glettonothing\m_tabl_tabulate_color_previous
      \or
-       \glet\m_tabl_tabulate_color_previous\empty
+       \glettonothing\m_tabl_tabulate_color_previous
      \or
        \glet\m_tabl_tabulate_color_previous\m_tabl_tabulate_color
      \or
@@ -1635,7 +1635,7 @@
    \directvskip\s_tabl_tabulate_separator
    \egroup}
 
-\let\m_tabl_tabulate_hrule_color\empty
+\lettonothing\m_tabl_tabulate_hrule_color
 
 \def\tabl_tabulate_hrule_preset_step#1%
   {\doifelsenumber{#1}%
@@ -1756,10 +1756,10 @@
 %      \registerparoptions
 %      \ifinsidefloat
 %        % that is, an unbreakable one
-%        \glet\tabl_tabulate_register_par_options\empty
+%        \glettonothing\tabl_tabulate_register_par_options
 %      \else
 %        % unsafe in crossing pages, at each b...
-%        % \glet\tabl_tabulate_register_par_options\empty
+%        % \glettonothing\tabl_tabulate_register_par_options
 %      \fi
 %    \fi}
 %
@@ -1774,10 +1774,10 @@
   {\registerparoptions
    \ifinsidefloat
      % that is, an unbreakable one
-     \glet\tabl_tabulate_register_par_options\empty
+     \glettonothing\tabl_tabulate_register_par_options
    \else
      % unsafe in crossing pages, at each b...
-     % \glet\tabl_tabulate_register_par_options\empty
+     % \glettonothing\tabl_tabulate_register_par_options
    \fi}
 
 \let\tabl_tabulate_register_par_options\relax
@@ -1806,7 +1806,7 @@
       \hss}}
 
 \def\tabl_tabulate_flush_indent
-  {\ifnum\c_tabl_tabulate_column=\zerocount
+  {\ifzero\c_tabl_tabulate_column
      \tabl_tabulate_flush_indent_indeed
    \fi}
 
@@ -2037,7 +2037,7 @@
      \expandafter\ignorepars % \ignorespaces
    \else
      % successive lines
-     \let\tabl_tabulate_eskip\empty
+     \lettonothing\tabl_tabulate_eskip
      \dontcomplain
      \glet\tabl_tabulate_hook\tabl_tabulate_hook_yes
      \expandafter\tabl_tabulate_splitoff_box
@@ -2047,7 +2047,7 @@
 \protected\def\tabl_tabulate_xeskip_second{\tabl_tabulate_eskip}
 
 \protected\def\tabl_tabulate_flush_second_indeed
-  {\glet\tabl_tabulate_flush_collected_indeed\empty
+  {\glettonothing\tabl_tabulate_flush_collected_indeed
    \global\c_tabl_tabulate_column\zerocount
    \tabl_tabulate_pbreak_check
    \dofastloopcs\c_tabl_tabulate_columns\tabl_tabulate_flush_second_step
@@ -2156,6 +2156,7 @@
 \permanent\def\tabl_tabulate_HL_second
   {\csname
      \ifnum\c_tabl_tabulate_noflines=\zerocount                     F\orelse
+   % \ifzeroc_tabl_tabulate_noflines                                F\orelse
      \ifnum\c_tabl_tabulate_noflines=\c_tabl_tabulate_totalnoflines L\else
                                                                     M\fi
    L\endcsname}
@@ -2213,8 +2214,8 @@
 %D places where we can use \LUA\ code (for instance in alignment of numbers. The
 %D repeat parser is replace at the \LUA\ end as well.
 
-\let\tabl_tabulate_flush_collected       \empty
-\let\tabl_tabulate_flush_collected_indeed\empty
+\lettonothing\tabl_tabulate_flush_collected
+\lettonothing\tabl_tabulate_flush_collected_indeed
 
 \let\v_tabl_tabulate_align\!!zerocount
 
@@ -2266,8 +2267,8 @@
    \ifx\p_synchronize\v!background
      \edef\currentframedcontent{\tabulationparameter\c!frame}%
      \ifx\currentframedcontent\v!off
-       \lettabulationparameter\c!frame\empty
-       \let\currentframedcontent\empty
+       \resettabulationparameter\c!frame
+       \lettonothing\currentframedcontent
        \letframedcontentparameter\c!frame\v!off
      \fi
      \letframedcontentparameter\c!synchronize\p_synchronize
@@ -2318,7 +2319,7 @@
    %
    \the\t_tabl_tabulate_initializers_first % collect more here
    %
-   \glet\tabl_tabulate_flush_collected\empty
+   \glettonothing\tabl_tabulate_flush_collected
    \ifdim\d_tabl_tabulate_margin>\zeropoint
      \t_tabl_tabulate_preamble
        {\aligntab
@@ -2398,7 +2399,7 @@
    \setbox\scratchbox\emptybox % free memory
    \ifconditional\c_tabl_tabulate_split
      \splittopskip\strutht
-     \glet\tabl_tabulate_flush_collected_indeed\empty
+     \glettonothing\tabl_tabulate_flush_collected_indeed
      \glet\tabl_tabulate_flush_collected\tabl_tabulate_flush_second
    \fi
    \c_tabl_tabulate_totalnoflines\c_tabl_tabulate_noflines
@@ -2714,7 +2715,7 @@
 \permanent\protected\defcsname starttabulate\endcsname
   {\bgroup % whole thing
    \settrue\c_tabl_generic
-   \let\currenttabulationparent\empty
+   \lettonothing\currenttabulationparent
    \tabl_start_regular}
 
 \permanent\letcsname stoptabulate\endcsname\relax % testcase cvs-002.tex
@@ -2829,11 +2830,11 @@
 %    \c!foregroundcolor=,
 %    \c!foregroundstyle=]
 
-\let\m_table_current_row_background              \empty
-\let\m_table_current_row_background_default      \empty
-\let\m_table_current_row_background_filler       \empty
-\let\m_table_current_row_background_defaultfiller\empty
-\let\m_table_current_row_background_auto         \empty
+\lettonothing\m_table_current_row_background
+\lettonothing\m_table_current_row_background_default
+\lettonothing\m_table_current_row_background_filler
+\lettonothing\m_table_current_row_background_defaultfiller
+\lettonothing\m_table_current_row_background_auto
 
 \protected\def\tabl_register_row_background#1%
   {\xdef\m_table_current_row_background{#1}}
@@ -2886,16 +2887,16 @@
    \fi}
 
 \appendtoks
-    \glet\m_table_current_row_background\empty
-    \glet\m_table_current_row_background_filler\empty
+    \glettonothing\m_table_current_row_background
+    \glettonothing\m_table_current_row_background_filler
     \global\c_tabl_tabulate_nofrealrows\zerocount
     \global\c_tabl_tabulate_autocolor\zerocount
     \clf_resetbackgroundrowdata
 \to \t_tabl_tabulate_initializers_first
 
 \appendtoks
-    \glet\m_table_current_row_background\empty
-    \glet\m_table_current_row_background_filler\empty
+    \glettonothing\m_table_current_row_background
+    \glettonothing\m_table_current_row_background_filler
     \global\c_tabl_tabulate_nofrealrows\zerocount
     \global\c_tabl_tabulate_autocolor\zerocount
     \clf_resetbackgroundrowdata
@@ -2906,8 +2907,8 @@
 \to \t_tabl_tabulate_every_real_row
 
 \appendtoks
-    \glet\m_table_current_row_background\empty
-    \glet\m_table_current_row_background_filler\empty
+    \glettonothing\m_table_current_row_background
+    \glettonothing\m_table_current_row_background_filler
 \to \t_tabl_tabulate_every_after_row
 
 \permanent\protected\def\tabl_tabulate_NL_first[#1]%
@@ -3003,7 +3004,7 @@
      \edef\m_table_current_row_background_auto{\tabulateparameter{\c!backgroundcolor:\number\c_tabl_tabulate_autocolor}}%
    \fi
    \ifempty\m_table_current_row_background_auto
-     \let\m_table_current_row_background_auto\empty % \m_table_current_row_background_default
+     \lettonothing\m_table_current_row_background_auto % \m_table_current_row_background_default
    \fi
    \tabl_register_row_background{\m_table_current_row_background_auto}}
 
@@ -3036,9 +3037,9 @@
 \to \t_tabl_tabulate_initializers_first
 
 \appendtoks
-   \edef\m_table_current_row_background_default       {\tabulateparameter\c!backgroundcolor}%
+   \edef\m_table_current_row_background_default{\tabulateparameter\c!backgroundcolor}%
    \edef\m_table_current_row_background_default_filler{\tabulateparameter\c!background}%
-   \let \m_table_current_row_background_auto           \empty
+   \lettonothing\m_table_current_row_background_auto
 \to \everytabulate
 
 \setuptabulate
diff --git a/tex/context/base/mkxl/tabl-tsp.mkxl b/tex/context/base/mkxl/tabl-tsp.mkxl
index 5f01e7eb4..51069b75f 100644
--- a/tex/context/base/mkxl/tabl-tsp.mkxl
+++ b/tex/context/base/mkxl/tabl-tsp.mkxl
@@ -69,16 +69,15 @@
 \newconditional\splitfloatdone
 \newconditional\onlyonesplitofffloat   \settrue\onlyonesplitofffloat
 
-\newif         \ifinsidesplitfloat   % will become conditional
+\newif   \ifinsidesplitfloat   % will become conditional
+\newcount\noffloatssplits
+\newtoks \everysplitfloatsetup
 
-\newcount      \noffloatssplits
-\newtoks       \everysplitfloatsetup
+\mutable\let\extrasplitfloatlines \!!zerocount
+\mutable\let\splitfloatfinalizer  \relax
 
-\mutable\let   \extrasplitfloatlines \!!zerocount
-\mutable\let   \splitfloatfinalizer  \relax
-\mutable\let   \splitfloatcommand    \empty
-
-\mutable\let   \floatcaptionsuffix   \empty
+\mutable\lettonothing\splitfloatcommand
+\mutable\lettonothing\floatcaptionsuffix
 
 \permanent\tolerant\protected\def\splitfloat[#1]#:#2% nog dubbele refs
   {\bgroup
@@ -134,7 +133,7 @@
    \global\advance\noffloatssplits\plusone
    \ifcase\noffloatssplits\relax \or
      \ifconditional\onlyonesplitofffloat
-       \let\floatcaptionsuffix\empty
+       \lettonothing\floatcaptionsuffix
      \fi
    \fi
    \bgroup
diff --git a/tex/context/base/mkxl/tabl-xtb.mklx b/tex/context/base/mkxl/tabl-xtb.mklx
index ceea878da..4f3d1683c 100644
--- a/tex/context/base/mkxl/tabl-xtb.mklx
+++ b/tex/context/base/mkxl/tabl-xtb.mklx
@@ -98,7 +98,7 @@
 \newcount\c_tabl_x_swapped
 \newcount\c_tabl_x_swapped_max
 
-\let\m_tabl_x_swapped_settings\empty
+\lettonothing\m_tabl_x_swapped_settings
 
 \aliased\let\currentxtablerow   \clf_x_table_r
 \aliased\let\currentxtablecolumn\clf_x_table_c
@@ -156,8 +156,8 @@
     \c!rightmargindistance=\zeropoint,% whole table
 ]
 
-\def\tabl_x_default_buffer{x_table_\number\c_tabl_x_nesting}
-\let\tabl_x_current_buffer\empty
+\def         \tabl_x_default_buffer{x_table_\number\c_tabl_x_nesting}
+\lettonothing\tabl_x_current_buffer
 
 \permanent\protected\def\startxtable{\tabl_x_start_table}
 
@@ -280,7 +280,7 @@
         footer              {\xtableparameter\c!footer}%
    \relax
    %
-   \letxtableparameter\c!option\empty
+   \resetxtableparameter\c!option
    % not so nice but needed as we use this in the setup
    \linewidth\xtableparameter\c!rulethickness\relax
    % so we freeze it
diff --git a/tex/context/base/mkxl/toks-aux.lmt b/tex/context/base/mkxl/toks-aux.lmt
index c152afb36..83e714d77 100644
--- a/tex/context/base/mkxl/toks-aux.lmt
+++ b/tex/context/base/mkxl/toks-aux.lmt
@@ -44,6 +44,7 @@ local function flags(t)
     if t.instance  then r[#r+1] = "instance"  end
     if t.tolerant  then r[#r+1] = "tolerant"  end
     if t.protected then r[#r+1] = "protected" end
+    if t.constant  then r[#r+1] = "constant"  end
     return r
 end
 
@@ -119,6 +120,7 @@ interfaces.implement {
                 elseif cn == "letter" or cn == "other char" then
                     wr(f3(id,cd,ix,cn,ix))
                 elseif cn == "match" then
+                    -- needs checking for additions
                     local s
                         if ix == 32 then s = "optional spacer"     -- space
                     elseif ix == 42 then s = "skip spaces"         -- *
diff --git a/tex/context/base/mkxl/trac-tex.mkxl b/tex/context/base/mkxl/trac-tex.mkxl
index 13c1a047f..5e1c9e5bc 100644
--- a/tex/context/base/mkxl/trac-tex.mkxl
+++ b/tex/context/base/mkxl/trac-tex.mkxl
@@ -24,7 +24,7 @@
 % \def\enabletextracerwhatever {...}
 % \def\disabletextracerwhatever{...}
 
-\mutable\let\alltextracers\empty % so that we can report available tracers
+\mutable\lettonothing\alltextracers % so that we can report available tracers
 
 \permanent\protected\def\installtextracer#1%
   {\addtocommalist{#1}\alltextracers}
diff --git a/tex/context/base/mkxl/type-ini.mklx b/tex/context/base/mkxl/type-ini.mklx
index bba2d433b..d750260e2 100644
--- a/tex/context/base/mkxl/type-ini.mklx
+++ b/tex/context/base/mkxl/type-ini.mklx
@@ -39,29 +39,29 @@
 \newtoks       \everybeforedefinetypeface
 \newtoks       \everyafterdefinetypeface
 
-\mutable\let\typescriptfiles   \empty
-\mutable\let\currenttypescripts\empty
-\mutable\let\currenttypefile   \empty
+\mutable\lettonothing\typescriptfiles
+\mutable\lettonothing\currenttypescripts
+\mutable\lettonothing\currenttypefile
 
 \installmacrostack\currenttypefile
 
-\mutable\let\typescriptone  \empty % public, used in typescripts
-\mutable\let\typescripttwo  \empty % public, used in typescripts
-\mutable\let\typescriptthree\empty % public, used in typescripts
+\mutable\lettonothing\typescriptone   % public, used in typescripts
+\mutable\lettonothing\typescripttwo   % public, used in typescripts
+\mutable\lettonothing\typescriptthree % public, used in typescripts
 
 \installmacrostack\typescriptone
 \installmacrostack\typescripttwo
 \installmacrostack\typescriptthree
 
-\mutable\let\fontclassstyle \empty
+\mutable\lettonothing\fontclassstyle
 
 \installmacrostack\fontclassstyle
 
-\let\m_font_typescripts_one  \empty
-\let\m_font_typescripts_two  \empty
-\let\m_font_typescripts_three\empty
-\let\m_font_typescripts_check\empty
-\let\m_font_typescripts_match\empty
+\lettonothing\m_font_typescripts_one
+\lettonothing\m_font_typescripts_two
+\lettonothing\m_font_typescripts_three
+\lettonothing\m_font_typescripts_check
+\lettonothing\m_font_typescripts_match
 
 \installmacrostack\m_font_typescripts_one
 \installmacrostack\m_font_typescripts_two
@@ -105,7 +105,7 @@
 
 \permanent\protected\def\usetypescriptfile[#filename]%
   {\ifcstok{#filename}\v!reset
-     \let\typescriptfiles\empty
+     \lettonothing\typescriptfiles
    \else
      \splitfilename{#filename}%
      \addtocommalist\splitoffbase\typescriptfiles
@@ -296,7 +296,7 @@
   {\let\typescriptone  \m_font_typescripts_one
    \let\typescripttwo  \m_font_typescripts_two
    \let\typescriptthree\m_font_typescripts_three
-   \let\m_font_typescripts_match\empty
+   \lettonothing\m_font_typescripts_match
    \doifelsenextoptionalcs\font_typescripts_start_process_one\font_typescripts_start_process_all}
 
 \def\font_typescripts_start_process_all % could be a \let
@@ -496,11 +496,11 @@
 
 \def\font_typefaces_defining_start#name#style#settings%
   {\let\m_ts_rscale    \!!plusone % as we push/pop
-   \let\m_ts_features  \empty
-   \let\m_ts_fallbacks \empty
-   \let\m_ts_goodies   \empty
-   \let\m_ts_direction \empty
-   \let\m_ts_designsize\empty
+   \lettonothing\m_ts_features
+   \lettonothing\m_ts_fallbacks
+   \lettonothing\m_ts_goodies
+   \lettonothing\m_ts_direction
+   \lettonothing\m_ts_designsize
    \geteparameters[m_ts_][#settings]% todo raw ... no need for key interpretation
    \push_macro_fontclass
    \push_macro_fontclassstyle
diff --git a/tex/context/base/mkxl/typo-ada.mkxl b/tex/context/base/mkxl/typo-ada.mkxl
index e8b37997b..beb03e264 100644
--- a/tex/context/base/mkxl/typo-ada.mkxl
+++ b/tex/context/base/mkxl/typo-ada.mkxl
@@ -27,7 +27,7 @@
 \newdimen\d_adaptive_line
 \newdimen\d_adaptive_hsize
 
-\mutable\let\m_adaptive_color\empty
+\mutable\lettonothing\m_adaptive_color
 
 \newbox\b_adaptive_box
 
@@ -70,7 +70,7 @@
    {\ifcase#1\dontleavehmode\fi
     \begingroup
     \ifhastok={#2}%
-      \let\currentadaptive\empty
+      \lettonothing\currentadaptive
       \setupcurrentadaptive[#2]%
     \else
       \edef\currentadaptive{#2}%
diff --git a/tex/context/base/mkxl/typo-del.mkxl b/tex/context/base/mkxl/typo-del.mkxl
index 5b8431070..f790f9907 100644
--- a/tex/context/base/mkxl/typo-del.mkxl
+++ b/tex/context/base/mkxl/typo-del.mkxl
@@ -314,9 +314,9 @@
 %D     \NC [fr:en] \NC {\tttf fr} \quotation[fr:en]{{\tttf <en=\currentlanguage>} something french} \NC \NR
 %D \stoptabulate
 
-\mutable\let\currentdelimitedlanguage\empty
-\mutable\let\innerdelimitedlanguage  \empty
-\mutable\let\outerdelimitedlanguage  \empty
+\mutable\lettonothing\currentdelimitedlanguage
+\mutable\lettonothing\innerdelimitedlanguage
+\mutable\lettonothing\outerdelimitedlanguage
 
 \installglobalmacrostack\currentdelimitedlanguage
 
@@ -344,11 +344,11 @@
        {\let\currentdelimitedlanguage\innerdelimitedlanguage}%
        \donothing
    \fi
-   \let\m_delimited_argument\empty}
+   \lettonothing\m_delimited_argument}
 
 \def\typo_delimited_set_language_yes_a
   {\let\currentdelimitedlanguage\m_delimited_argument
-   \let\m_delimited_argument\empty}
+   \lettonothing\m_delimited_argument}
 
 \def\typo_delimited_push#1#2%
   {\push_macro_currentdelimitedtext     % can we combine these two
diff --git a/tex/context/base/mkxl/typo-dir.mkxl b/tex/context/base/mkxl/typo-dir.mkxl
index af680282c..a5a4bc568 100644
--- a/tex/context/base/mkxl/typo-dir.mkxl
+++ b/tex/context/base/mkxl/typo-dir.mkxl
@@ -51,8 +51,8 @@
 
 % maybe use chardefs
 
-\mutable\let\currentbidimode\empty
-\mutable\let\currentbidistamp\empty
+\mutable\lettonothing\currentbidimode
+\mutable\lettonothing\currentbidistamp
 
 \def\typo_dir_get_mode
   {\def\currentbidimode{\clf_getbidimode % test edef
diff --git a/tex/context/base/mkxl/typo-itm.mkxl b/tex/context/base/mkxl/typo-itm.mkxl
index 7ae1b732f..1622866ce 100644
--- a/tex/context/base/mkxl/typo-itm.mkxl
+++ b/tex/context/base/mkxl/typo-itm.mkxl
@@ -103,7 +103,7 @@
    \ifempty\p_typo_items_symbol
      \let\m_typo_items_symbol\firstofoneargument
    \orelse\ifx\p_typo_items_symbol\v!none
-     \let\p_typo_items_symbol\empty
+     \lettonothing\p_typo_items_symbol
      \let\m_typo_items_symbol\firstofoneargument
    \else
      \doifelseconversiondefined\p_typo_items_symbol
diff --git a/tex/context/base/mkxl/typo-mar.mkxl b/tex/context/base/mkxl/typo-mar.mkxl
index 242797a5d..c49f8824f 100644
--- a/tex/context/base/mkxl/typo-mar.mkxl
+++ b/tex/context/base/mkxl/typo-mar.mkxl
@@ -142,10 +142,10 @@
 \newconditional\inhibitmargindata      % This one is used at the Lua end!
 \newtoks       \everymargindatacontent % Later on we will set this one.
 
-\mutable\let\currentmargindatastrut  \empty
-\mutable\let\currentmargindatawidth  \empty
-\mutable\let\currentmarginfirstheight\empty
-\mutable\let\currentmarginreference  \empty
+\mutable\lettonothing\currentmargindatastrut
+\mutable\lettonothing\currentmargindatawidth
+\mutable\lettonothing\currentmarginfirstheight
+\mutable\lettonothing\currentmarginreference
 
 \appendtoks
     \settrue\inhibitmargindata
@@ -239,7 +239,7 @@
            \margindataparameter\c!command{#content}%
            \endstrut
          \egroup
-         \let\currentmarginfirstheight\empty
+         \lettonothing\currentmarginfirstheight
        \else
          \setbox\nextbox\naturalhbox \currentmarginreference \bgroup
            \typo_margins_data_synchronize
diff --git a/tex/context/base/mkxl/typo-shp.mkxl b/tex/context/base/mkxl/typo-shp.mkxl
index 3f1d3f3d8..64cacef09 100644
--- a/tex/context/base/mkxl/typo-shp.mkxl
+++ b/tex/context/base/mkxl/typo-shp.mkxl
@@ -77,7 +77,7 @@
 
 % \permanent\protected\tolerant\def\startshapedparagraph[#1]% no grouping
 %   {\begingroup
-%    \let\currentshapedparagraph\empty
+%    \lettonothing\currentshapedparagraph
 %    \setupshapedparagraph[#1]%
 %    \edef\p_mp    {\shapedparagraphparameter\c!mp}%
 %    \edef\p_repeat{\shapedparagraphparameter\c!repeat}%
@@ -154,7 +154,7 @@
 
 \permanent\protected\tolerant\def\startshapedparagraph[#1]% no grouping
   {\begingroup
-   \let\currentshapedparagraph\empty
+   \lettonothing\currentshapedparagraph
    \setupshapedparagraph[#1]%
    \setlocalhsize
    \doifsomething{\shapedparagraphparameter\c!text}
diff --git a/tex/context/base/mkxl/typo-wrp.mkxl b/tex/context/base/mkxl/typo-wrp.mkxl
index 850d42e78..71559a8a3 100644
--- a/tex/context/base/mkxl/typo-wrp.mkxl
+++ b/tex/context/base/mkxl/typo-wrp.mkxl
@@ -52,7 +52,7 @@
   {\wordboundary\strut}
 
 \appendtoks
-    \let\spac_crlf_placeholder\empty
+    \lettonothing\spac_crlf_placeholder
 \to \everysetnostrut
 
 \appendtoks
diff --git a/tex/context/modules/mkxl/s-publications-show.mkxl b/tex/context/modules/mkxl/s-publications-show.mkxl
index 9f4098489..f4967f7e4 100644
--- a/tex/context/modules/mkxl/s-publications-show.mkxl
+++ b/tex/context/modules/mkxl/s-publications-show.mkxl
@@ -26,9 +26,9 @@
 
 \tolerant\gdef\publ_show_dataset_whatever#1[#2]%
   {\begingroup
-   \letdummyparameter\c!specification\currentbtxspecification
-   \setdummyparameter\c!dataset      {\currentbtxdataset}%
-   \letdummyparameter\c!field        \empty
+   \letdummyparameter  \c!specification\currentbtxspecification
+   \setdummyparameter  \c!dataset      {\currentbtxdataset}%
+   \resetdummyparameter\c!field
    \ifparameter#2\or
      \ifhastok={#2}%
        \getdummyparameters[#2]%
diff --git a/tex/context/modules/mkxl/x-mathml.mkxl b/tex/context/modules/mkxl/x-mathml.mkxl
index 12ddf2586..ea3052d2d 100644
--- a/tex/context/modules/mkxl/x-mathml.mkxl
+++ b/tex/context/modules/mkxl/x-mathml.mkxl
@@ -283,7 +283,7 @@
 
 \newcount\@MMLlevel \def\MMLcreset{\@MMLlevel\zerocount}
 
-\let\MMLctempresetlist\empty \def\setMMLcreset{\edef\MMLctempresetlist}
+\lettonothing\MMLctempresetlist \def\setMMLcreset{\edef\MMLctempresetlist}
 
 \let\MMLdoL\donothing
 \let\MMLdoR\donothing
@@ -311,7 +311,7 @@
            \edef\MMLdoL{\noexpand\left \mmlapplyopentoken }
            \edef\MMLdoR{\noexpand\right\mmlapplyclosetoken}
         \fi
-        \let\MMLctempresetlist\empty
+        \lettonothing\MMLctempresetlist
         \xmldoifelse {#1} {/mml:apply} {
 %             % <apply> <apply> ... </apply> <ci> .. </ci> </apply>
 %             \xmldoifelse {#1} {/mml:apply(mml:plus|mml:minus)} {% [a]
@@ -571,7 +571,7 @@
 \startxmlsetups mml:cn:integer
     \mathatom class \mathdigitcode \bgroup
         \edef\mmlintegerbase{\xmlattdef{#1}{base}{}}
-        \ifx\mmlintegerbase\empty
+        \ifempty\mmlintegerbase
             \xmlflush{#1}
         \else
             \mtext {
@@ -976,7 +976,7 @@
 
 \setupMMLappearance[power][\c!reduction=\v!yes]
 
-\let\MMLpowerelement\empty
+\lettonothing\MMLpowerelement
 
 \startxmlsetups mml:power
     \xmldoifelse {#1} {/mml:apply}  {
@@ -1479,12 +1479,12 @@
             }
         }
     } {
-        \let\mmlsumprodlower\empty
+        \lettonothing\mmlsumprodlower
     }
     \xmldoifelse {#1} {/mml:uplimit} {
         \def\mmlsumprodupper{\normalsuperscript{\xmlfirst{#1}{/mml:uplimit}}}
     } {
-        \let\mmlsumprodupper\empty
+        \lettonothing\mmlsumprodupper
     }
    \xmldoif {#1} {/mml:interval} { % open math converter gives this
         \edef\mmlintervalfrom{\xmlindex{#1}{/mml:interval}{1}}
@@ -1754,7 +1754,7 @@
     \else
         \normalsuperscript{\ifconditional\xmlinversefunction-\fi\MMLpowerelement}
         \setfalse\xmlinversefunction
-        \glet\MMLpowerelement\empty
+        \glettonothing\MMLpowerelement
     \fi
     \xmlsetup{#1}{mml:function:argument}
 \stopxmlsetups
@@ -2364,14 +2364,14 @@
             \scratchwidth \xmlattdef{#1}{width} \!!zeropoint % must be string
             \scratchheight\xmlattdef{#1}{height}\!!zeropoint
             \scratchdepth \xmlattdef{#1}{depth} \!!zeropoint
-            \ifdim\scratchheight=\zeropoint
-                \ifdim\scratchdepth=\zeropoint\else
+            \ifzeropt\scratchheight
+                \ifzeropt\scratchdepth\else
                     \novrule\s!depth\scratchdepth\s!height\zeropoint\s!width\zeropoint
                 \fi
             \else
                 \novrule\s!depth\zeropoint\s!height\scratchheight\s!width\zeropoint
             \fi
-            \ifdim\scratchwidth=\zeropoint
+            \ifzeropt\scratchwidth
                 % maybe we need to do it anyway
             \orelse\ifx\MMLmspaceoption\v!test
                 \hbox to \scratchwidth{\showstruts\strut\hss\lower2\exheight\hbox{\infofont\xmlattdef{#1}{width}}\hss\strut}
diff --git a/tex/generic/context/luatex/luatex-fonts-merged.lua b/tex/generic/context/luatex/luatex-fonts-merged.lua
index 8536adc85..d3fd3dbfe 100644
--- a/tex/generic/context/luatex/luatex-fonts-merged.lua
+++ b/tex/generic/context/luatex/luatex-fonts-merged.lua
@@ -1,6 +1,6 @@
 -- merged file : c:/data/develop/context/sources/luatex-fonts-merged.lua
 -- parent file : c:/data/develop/context/sources/luatex-fonts.lua
--- merge date  : 2022-12-09 16:31
+-- merge date  : 2022-12-15 17:49
 
 do -- begin closure to overcome local limits and interference
author	Hans Hagen <pragma@wxs.nl>	2022-12-15 19:13:44 +0100
committer	Context Git Mirror Bot <phg@phi-gamma.net>	2022-12-15 19:13:44 +0100
commit	8f472c629a996f1c08281198210354a253d7f56b (patch)
tree	26f5fa0bda520d7ea9e87947df6978b9085a7d58 /tex
parent	3bdc9b9072bba774cd5c604fe185d39ddbdc911e (diff)
download	context-8f472c629a996f1c08281198210354a253d7f56b.tar.gz