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Diffstat (limited to 'doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex')
| -rw-r--r-- | doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex | 271 |
1 files changed, 175 insertions, 96 deletions
diff --git a/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex b/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex index a233bf630..ee30683e8 100644 --- a/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex +++ b/doc/context/sources/general/manuals/luametatex/luametatex-enhancements.tex @@ -35,8 +35,8 @@ assigned to them at this early time (giving a \quote {Missing number} error), so it may be needed to put these assignments before the above line: \starttyping -\catcode `\{=1 -\catcode `\}=2 +\catcode `\{ = 1 +\catcode `\} = 2 \stoptyping More fine|-|grained primitives control is possible and you can look up the @@ -819,103 +819,123 @@ but faster (only measurable with millions of calls) and probably more convenient \stopsubsection -\startsubsection[title={\lpr {expanded}, \lpr {immediateassignment} and \lpr {immediateassigned}}] +\startsubsection[title={\lpr {expanded}}] \topicindex {expansion} -The \lpr {expanded} primitive takes a token list and expands its content which can -come in handy: it avoids a tricky mix of \prm {expandafter} and \prm {noexpand}. -You can compare it with what happens inside the body of an \prm {edef}. But this -kind of expansion still doesn't expand some primitive operations. - -\startbuffer -\newcount\NumberOfCalls - -\def\TestMe{\advance\NumberOfCalls1 } - -\edef\Tested{\TestMe foo:\the\NumberOfCalls} -\edef\Tested{\TestMe foo:\the\NumberOfCalls} -\edef\Tested{\TestMe foo:\the\NumberOfCalls} - -\meaning\Tested -\stopbuffer - -\typebuffer - -The result is a macro that has the not expanded code in its body: - -\getbuffer - -Instead we can define \tex {TestMe} in a way that expands the assignment -immediately. You need of course to be aware of preventing look ahead interference -by using a space or \tex {relax} (often an expression works better as it doesn't -leave an \tex {relax}). - -\startbuffer -\def\TestMe{\immediateassignment\advance\NumberOfCalls1 } - -\edef\Tested{\TestMe foo:\the\NumberOfCalls} -\edef\Tested{\TestMe foo:\the\NumberOfCalls} -\edef\Tested{\TestMe foo:\the\NumberOfCalls} - -\meaning\Tested -\stopbuffer - -\typebuffer - -This time the counter gets updates and we don't see interference in the -resulting \tex {Tested} macro: - -\getbuffer - -Here is a somewhat silly example of expanded comparison: - -\startbuffer -\def\expandeddoifelse#1#2#3#4% - {\immediateassignment\edef\tempa{#1}% - \immediateassignment\edef\tempb{#2}% - \ifx\tempa\tempb - \immediateassignment\def\next{#3}% - \else - \immediateassignment\def\next{#4}% - \fi - \next} - -\edef\Tested - {(\expandeddoifelse{abc}{def}{yes}{nop}/% - \expandeddoifelse{abc}{abc}{yes}{nop})} - -\meaning\Tested -\stopbuffer - -\typebuffer - -It gives: - -\getbuffer - -A variant is: +The \lpr {expanded} primitive takes a token list and expands its content which +can come in handy: it avoids a tricky mix of \prm {expandafter} and \prm +{noexpand}. You can compare it with what happens inside the body of an \prm +{edef}. The \tex {immediateassignment} and \tex {immediateassigned} commands are +gone because we have the more powerful local control commands. They are a tad +slower but this mechanism isn't used that much anyway. Inside an \prm {edef} you +can use the \type {\immediate} prefix anyway, so if you really want these +primitives back you can say: \starttyping -\def\expandeddoifelse#1#2#3#4% - {\immediateassigned{ - \edef\tempa{#1}% - \edef\tempb{#2}% - }% - \ifx\tempa\tempb - \immediateassignment\def\next{#3}% - \else - \immediateassignment\def\next{#4}% - \fi - \next} +\let\immediateassignment\immediate +\let\immediateassigned \localcontrolled \stoptyping -The possible error messages are the same as using assignments in preambles of -alignments and after the \prm {accent} command. The supported assignments are the -so called prefixed commands (except box assignments). - \stopsubsection +% \startsubsection[title={\lpr {expanded}, \lpr {immediateassignment} and \lpr {immediateassigned}}] +% +% \topicindex {expansion} +% +% The \lpr {expanded} primitive takes a token list and expands its content which can +% come in handy: it avoids a tricky mix of \prm {expandafter} and \prm {noexpand}. +% You can compare it with what happens inside the body of an \prm {edef}. But this +% kind of expansion still doesn't expand some primitive operations. +% +% \startbuffer +% \newcount\NumberOfCalls +% +% \def\TestMe{\advance\NumberOfCalls1 } +% +% \edef\Tested{\TestMe foo:\the\NumberOfCalls} +% \edef\Tested{\TestMe foo:\the\NumberOfCalls} +% \edef\Tested{\TestMe foo:\the\NumberOfCalls} +% +% \meaning\Tested +% \stopbuffer +% +% \typebuffer +% +% The result is a macro that has the not expanded code in its body: +% +% \getbuffer +% +% Instead we can define \tex {TestMe} in a way that expands the assignment +% immediately. You need of course to be aware of preventing look ahead interference +% by using a space or \tex {relax} (often an expression works better as it doesn't +% leave an \tex {relax}). +% +% \startbuffer +% \def\TestMe{\immediateassignment\advance\NumberOfCalls1 } +% +% \edef\Tested{\TestMe foo:\the\NumberOfCalls} +% \edef\Tested{\TestMe foo:\the\NumberOfCalls} +% \edef\Tested{\TestMe foo:\the\NumberOfCalls} +% +% \meaning\Tested +% \stopbuffer +% +% \typebuffer +% +% This time the counter gets updates and we don't see interference in the +% resulting \tex {Tested} macro: +% +% \getbuffer +% +% Here is a somewhat silly example of expanded comparison: +% +% \startbuffer +% \def\expandeddoifelse#1#2#3#4% +% {\immediateassignment\edef\tempa{#1}% +% \immediateassignment\edef\tempb{#2}% +% \ifx\tempa\tempb +% \immediateassignment\def\next{#3}% +% \else +% \immediateassignment\def\next{#4}% +% \fi +% \next} +% +% \edef\Tested +% {(\expandeddoifelse{abc}{def}{yes}{nop}/% +% \expandeddoifelse{abc}{abc}{yes}{nop})} +% +% \meaning\Tested +% \stopbuffer +% +% \typebuffer +% +% It gives: +% +% \getbuffer +% +% A variant is: +% +% \starttyping +% \def\expandeddoifelse#1#2#3#4% +% {\immediateassigned{ +% \edef\tempa{#1}% +% \edef\tempb{#2}% +% }% +% \ifx\tempa\tempb +% \immediateassignment\def\next{#3}% +% \else +% \immediateassignment\def\next{#4}% +% \fi +% \next} +% \stoptyping +% +% The possible error messages are the same as using assignments in preambles of +% alignments and after the \prm {accent} command. The supported assignments are the +% so called prefixed commands (except box assignments). +% +% \stopsubsection + \startsubsection[title={\lpr {ignorepars}}] This primitive is like \prm {ignorespaces} but also skips paragraph ending @@ -1291,6 +1311,24 @@ the acceptable range is from 0 to 65535. \stopsubsection +\startsubsection[title={\prm {hrule} and \prm {vrule}}] + +\topicindex {rules} + +Both rule drawing commands take an optional \type {xoffset} and \type {yoffset} +parameter. The displacement is virtual and not taken into account when the +dimensions are calculated. + +\stopsubsection + +\topicindex {splitting} + +The \prm {vsplit} primitive has to be followed by a specification of the required +height. As alternative for the \type {to} keyword you can use \type {upto} to get +a split of the given size but result has the natural dimensions then. + +\stopsubsection + \startsubsection[title={\prm {vsplit}}] \topicindex {splitting} @@ -1317,12 +1355,12 @@ point this approach was abandoned and a more natural trick was used: images (and box resources) became a special kind of rules, and as rules already have dimensions, the code could be simplified. -When direction nodes and localpar nodes also became first class nodes, whatsits -again became just that: nodes representing whatever you want, but without -dimensions, and therefore they could again be ignored when dimensions mattered. -And, because images were disguised as rules, as mentioned, their dimensions -automatically were taken into account. This seperation between front and backend -cleaned up the code base already quite a bit. +When direction nodes and (formerly local) par nodes also became first class +nodes, whatsits again became just that: nodes representing whatever you want, but +without dimensions, and therefore they could again be ignored when dimensions +mattered. And, because images were disguised as rules, as mentioned, their +dimensions automatically were taken into account. This separation between front +and backend cleaned up the code base already quite a bit. In \LUAMETATEX\ we still have the image specific subtypes for rules, but the engine never looks at subtypes of rules. That was up to the backend. This means @@ -1843,6 +1881,47 @@ take some time (and user input).} \stopsection +\startsection[title=Keywords] + +Some primitives accept one or more keywords and \LUAMETATEX\ adds some more. In +order to deal with this efficiently the keyword scanner has been optimized, where +even the context was taken into account. As a result the scanner was quite a bit +faster. This kind of optimization was a graduate process the eventually ended up +in what we have now. In traditional \TEX\ (and also \LUATEX) the order of +keywords is sometimes mixed and sometimes prescribed. In most cases only one +occurrence is permitted. So, for instance, this is valid in \LUATEX: + +\starttyping +\hbox attr 123 456 attr 123 456 spread 10cm { } +\hrule width 10cm depth 3mm +\hskip 3pt plus 2pt minus 1pt +\stoptyping + +The \type {attr} comes before the \type {spread}, rules can have multiple mixed +dimension specifiers, and in glue the optional \type {minus} part always comes +last. The last two commands are famous for look ahead side effects which is why +macro packages will end them with something not keyword, like \type {\relax}, +when needed. + +In \LUAMETATEX\ the following is okay. Watch the few more keywords in box and +rule specifications. + +\starttyping +\hbox reverse to 10cm attr 123 456 orientation 4 xoffset 10pt spread 10cm { } +\hrule xoffset 10pt width 10cm depth 3mm +\hskip 3pt minus 1pt plus 2pt +\stoptyping + +Here the order is not prescribed and, as demonstrated with the box specifier, for +instance dimensions (specified by \type {to} or \type {spread} can be overloaded +by later settings. In case you wonder if that breaks compatibility: in some way +it does but bad or sloppy keyword usage breaks a run anyway. For instance \type +{minuscule} results in \type {minus} with no dimension being seen. So, in the end +the user should not noticed it and when a user does, the macro package already +had an issue that had to be fixed. + +\stopsection + \startsection[title=Expressions] The \type {*expr} parsers now accept \type {:} as operator for integer division |