Hi Wolfgang! ···<date: 2012-06-07, Thursday>···<from: Wolfgang Schuster>···
>
> 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}
Thanks very much. This solves my problem. Very convenient that I
can rewrite it to use commacommand.
Philipp
>
> \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
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___________________________________________________________________________________ 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 ___________________________________________________________________________________
