From e0c6872cf40896c7be36b11dcc744620f10adf1d Mon Sep 17 00:00:00 2001 From: Norbert Preining Date: Mon, 2 Sep 2019 13:46:59 +0900 Subject: Initial commit --- macros/generic/misc/mathlig.tex | 131 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 131 insertions(+) create mode 100644 macros/generic/misc/mathlig.tex (limited to 'macros/generic/misc/mathlig.tex') diff --git a/macros/generic/misc/mathlig.tex b/macros/generic/misc/mathlig.tex new file mode 100644 index 0000000000..04194b8493 --- /dev/null +++ b/macros/generic/misc/mathlig.tex @@ -0,0 +1,131 @@ +% +% mathlig.tex +% +% (c) 2001 Jules Bean +% Permission is granted to freely use, copy, and distribute +% without restriction. Permission is also granted to distribute +% modified versions and incorporate into your own macro packages +% if a brief acknowledgement is given. +% +% Version 1.0 11 May 2001 + +% Define 'mathmode' ligatures, as in +% +%\mathlig{->}{\rightarrow} +%\mathlig{<-}{\leftarrow} +%\mathlig{<->}{\leftrightarrow} +% +% Works even if they have common prefixes (takes the longest match, +% then backtracks). +% +% Can be used to create ligatures even if the second +% and subsequent characters have weird catcodes, but I don't recommend +% it. + +\count255\catcode`@ +\catcode`@=11 +\chardef\mathlig@atcode\count255 + +% Let or def an 'active' version of a token. Thanks to Donald +% Arseneau and groups.google.com +\def\actively#1#2{\begingroup\uccode`\~=`#2\relax\uppercase{\endgroup#1~}} +% Eat the next token, and then pass control to mathlig@next@cmd +\def\mathlig@gobble{\afterassignment\mathlig@next@cmd\let\mathlig@next= } +% Used to delimit delimited arguments, and ifx tests for emptyness. +\def\mathlig@delim{\mathlig@delim} +% Some macros to help dealing with 'computed names' (csnames). +% Just like def, but first parameter is evaluated as a csname +\def\mathlig@defcs#1{\expandafter\def\csname#1\endcsname} +% A version of \let +\def\mathlig@let@cs#1#2{\expandafter\let\expandafter#1\csname#2\endcsname} +% Maintain a 'list' of tokens as a macro which expands to them +\def\mathlig@appendcs#1#2{\expandafter\edef\csname#1\endcsname{\csname#1\endcsname#2}} + +% The main externally visible macro. +% Defines '#1' as a 'ligature' to expand to #2 +% First uses \mathlig@checklig to make sure that all initial segments of +% #1 as set up as ligatures. +% Then sets the ligature #1 to expand to #2. +\def\mathlig#1#2{\mathlig@checklig#1\mathlig@end\mathlig@defcs{mathlig@back@#1}{#2}\ignorespaces} + +% All the @check macros should be idempotent: they set up the definitions +% only if it hasn't already been done. + +%Check #1#2 can be a ligature: +% Check #1 is math-active. +% If not, save the mathcode, set the macros #1 +%Now check the suffix tables with \checkrest +\def\mathlig@checklig#1#2\mathlig@end{% + \expandafter\ifx\csname mathlig@forw@#1\endcsname\relax + \expandafter\mathchardef\csname mathlig@back@#1\endcsname=\mathcode`#1% + \mathcode`#1"8000\actively\def#1{\csname mathlig@look@#1\endcsname}% + \mathlig@dolig#1\mathlig@delim +\fi +\mathlig@checksuffix#1#2\mathlig@end +} + +%Two-part macro. +%Check suffix tables. If #2 is empty, no suffix! +%Otherwise, we make sure #2 is a valid suffix for #1, +%then recurse for #3 on #1#2 +\def\mathlig@checksuffix#1#2\mathlig@end{% +\ifx\mathlig@delim#2\mathlig@delim\relax\else\mathlig@checksuffix@{#1}#2\mathlig@end\fi +} +\def\mathlig@checksuffix@#1#2#3\mathlig@end{% +\expandafter\ifx\csname mathlig@forw@#1#2\endcsname\relax\mathlig@dosuffix{#1}{#2}\fi +\mathlig@checksuffix{#1#2}#3\mathlig@end +} + +% The do macros should not be called more than once for a given ligature. + +% Add #2 to the list of valid suffixes for #1 +% Then make the ligature for #1#2 one which only backtracks, for now +\def\mathlig@dosuffix#1#2{% +\mathlig@appendcs{mathlig@toks@#1}{#2}% +\mathlig@dolig{#1}{#2}\mathlig@delim +} + +% Setup #1#2 so that ligatures beginning #1#2 work. +% Such ligatures will look at what's coming next (in case +% of a longer ligature) and, failing that, +% backtrack to just #1 + +\def\mathlig@dolig#1#2\mathlig@delim{% +%The look macro just \futurelets what's coming up and +%then passes control to forw + \mathlig@defcs{mathlig@look@#1#2}{% + \mathlig@let@cs\mathlig@next{mathlig@forw@#1#2}\futurelet\mathlig@next@tok\mathlig@next}% +%The forw macro uses chck to try all possible suffixes, passing control +%either to one of those, or to the back macro + \mathlig@defcs{mathlig@forw@#1#2}{% + \mathlig@let@cs\mathlig@next{mathlig@back@#1#2}% + \mathlig@let@cs\checker{mathlig@chck@#1#2}% + \mathlig@let@cs\mathligtoks{mathlig@toks@#1#2}% + \expandafter\ifx\expandafter\mathlig@delim\mathligtoks\mathlig@delim\relax\else + \expandafter\checker\mathligtoks\mathlig@delim\fi + \mathlig@next + }% +%The toks macro just stores the suffixes + \mathlig@defcs{mathlig@toks@#1#2}{}% +%The chk macro goes through the suffixes one by one +%tail recursing until it runs out, or finds one. + \mathlig@defcs{mathlig@chck@#1#2}##1##2\mathlig@delim{% + %\message{Lig so far '#1#2', checking for '##1'}% + \ifx\mathlig@next@tok##1% + \mathlig@let@cs\mathlig@next@cmd{mathlig@look@#1#2##1}\let\mathlig@next\mathlig@gobble + \fi + \ifx\mathlig@delim##2\mathlig@delim\relax\else + \csname mathlig@chck@#1#2\endcsname##2\mathlig@delim + \fi + }% +% +% The back macro, defined only if this is a ligature of at least +% two characters, is a default fallback: go back to the previous char. +% (If this is a ligature of only one character, the mathcode will have +% been saved and set as the fallback elsewhere) + \ifx\mathlig@delim#2\mathlig@delim\else + \mathlig@defcs{mathlig@back@#1#2}{\csname mathlig@back@#1\endcsname #2}% + \fi +}% + +\catcode`@\mathlig@atcode -- cgit v1.2.3