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:
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\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
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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?
I’d be grateful for any advice
Philipp
PS: Yeah, I could use Lua for it but that’s not the question.
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