1 files changed, 31 insertions, 2 deletions
diff --git a/tex/context/base/syst-aux.lua b/tex/context/base/syst-aux.lua
index 7fd25d6ab..cda340cb6 100644
--- a/tex/context/base/syst-aux.lua
+++ b/tex/context/base/syst-aux.lua
@@ -6,19 +6,37 @@ if not modules then modules = { } end modules ['syst-aux'] = {
     license   = "see context related readme files"
 }
 
+-- slower than lpeg:
+--
+-- utfmatch(str,"(.?)(.*)$")
+-- utf.sub(str,1,1)
+
+local commands, context = commands, context
+
 local settings_to_array = utilities.parsers.settings_to_array
 local concat = table.concat
+local format = string.format
+local utfsub = utf.sub
+local P, C, Carg, lpegmatch, utf8char = lpeg.P, lpeg.C, lpeg.Carg, lpeg.match, lpeg.patterns.utf8char
 
 local setvalue = context.setvalue
 
+local pattern = C(utf8char^-1) * C(P(1)^0)
+
 function commands.getfirstcharacter(str)
-    local first, rest = utf.match(str,"(.?)(.*)$")
+    local first, rest = lpegmatch(pattern,str)
     setvalue("firstcharacter",first)
     setvalue("remainingcharacters",rest)
 end
 
+local pattern = C(utf8char^-1)
+
 function commands.doiffirstcharelse(chr,str)
-    commands.doifelse(utf.sub(str,1,1) == chr)
+    commands.doifelse(lpegmatch(pattern,str) == chr)
+end
+
+function commands.getsubstring(str,first,last)
+    context(utfsub(str,tonumber(first),tonumber(last)))
 end
 
 -- function commands.addtocommalist(list,item)
@@ -50,3 +68,14 @@ end
 --         end
 --     end
 -- end
+
+local pattern = (C((1-P("%"))^1) * Carg(1)) /function(n,d) return format("%.0fsp",d * tonumber(n)/100) end * P("%") * P(-1)
+
+-- commands.percentageof("10%",65536*10)
+
+function commands.percentageof(str,dim)
+    context(lpegmatch(pattern,str,1,dim) or str)
+end
+
+-- \gdef\setpercentdimen#1#2%
+--   {#1=\ctxcommand{percentageof("#2",\number#1)}\relax}