Am 07.06.2012 um 17:34 schrieb Philipp Gesang:
> 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 comma command.
You can also try to use a Lua variant.
\def\states_entry_indeed[#1][#2]%
{\startlua
local entries = utilities.parsers.settings_to_array("#1")
local entry = entries[#2]
if entry then
context(entry)
else
context("\\tttf NO ENTRY!")
end
\stoplua}
Wolfgang
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