Am 07.06.2012 um 14:05 schrieb Philipp Gesang: > Hi all, > > my goal is a macro \definestates[foo][...,...] which takes a comma > list and creates a monadic macro \foo[n]. \foo[n] should return > either the nth item or, if (n > list length), a default. I > thought the right tools were \processcommalist to generate the > mapping n-><list item>, as well as \processaction to retrieve the > items. But naively I didn’t consider expansion ... > > My code so far: > > ··8<···································································· > \unprotect > > \def\definestates{\dodoubleempty\do_define_states} > > \def\do_define_states[#1][#2]{% > \expandafter\edef\csname#1_states\endcsname{% > \nstates0 > %% this is supposed to be expanded so we employ the \raw... variety > \rawprocesscommalist[#2]\add_one_state% > unknown=>\dummystate,% > default=>\dummystate,% > }% > \do_do_define_states{#1}% > } > > \let\dummystate\empty > > \newcount\nstates > \unexpanded\def\add_one_state#1{% > \advance\nstates\plusone > \the\nstates=>#1,% > } > > \def\do_do_define_states#1{% > \expandafter\def\csname#1\endcsname > {\expandafter\dosingleempty\csname do_#1\endcsname}% > \expandafter\def\csname do_#1\endcsname[##1]{% > \iffirstargument > % <[DBG] cmd:#1, state:##1>\par > \edef\currentstates{\csname#1_states\endcsname}% > %% At this point \currentstates should yield the whole mapping so > %% we can use it with \processaction. But ... > % \show\currentstates > % \currentstates\par > %% ... here it still contains > %% \nstates 0 \rawprocesscommalist [foo,bar,baz] ... > %% and the next directive has an empty result: > \rawprocessaction[##1][\currentstates]% > \fi > }% > } > > \protect > \starttext > > \definestates[mystates][foo,bar,baz] > %% At this point I’d like \mystates_states to contain (literally) > %% “1=>foo,2=>bar,3=>baz,unknown=>,default=>,” > %% so the following command > \mystates[1] % -> foo > %% would be equivalent to > %% \processaction[1][1=>foo,2=>bar,3=>baz,unknown=>,default=>,] > \mystates[2] % -> bar > \mystates[42] % -> dummy > > \stoptext > ··8<···································································· > > My question: How can I use \[raw]processcommalist in an expanded > definition? How can I get \[raw]processcommalist to operate on > the expansion of its second argument? Does this even make sense? > If not, what is the proper way?
\unprotect \unexpanded\def\definestates {\dodoubleargument\definestates_indeed} \def\definestates_indeed[#1][#2]% {\setuevalue{#1}{\states_entry[#2]}} \unexpanded\def\states_entry {\dodoubleargument\states_entry_indeed} \def\states_entry_indeed[#1][#2]% {\getcommalistsize[#1]% \ifnum#2>\commalistsize {\tttf NO ENTRY!}% \else \getfromcommalist[#1][#2]\commalistelement \fi} \protect \starttext \definestates[mystates][foo,bar,baz] \starttabulate \NC 2 \EQ \mystates [2] \NC\NR \NC 42 \EQ \mystates[42] \NC\NR \stoptabulate \stoptext Wolfgang ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___________________________________________________________________________________