[NTG-context] Re: using command line arguments

[Wolfgang Schuster <wolfgang.schuster.lists@gmail.com>]

Henning Hraban Ramm schrieb am 28.10.2024 um 16:26:
> Am 28.10.24 um 16:18 schrieb Wolfgang Schuster:
>> Henning Hraban Ramm schrieb am 28.10.2024 um 12:18:
>>> Hi, I’m trying to use a command line argument in parameter names – 
>>> color name in the example below, variable namespace in my actual 
>>> project.
>>> I guess I need more expansion, but where?
>>> Or what’s the problem here?
>>>
>>> """
>>> \setupbodyfont[plex,18pt]
>>>
>>> % set \OEM to the parameter name, fall back to "fiee"
>>> \expanded\define\OEM{\expanded\doifelsedocumentargument{OEM} 
>>> {\expanded\getdocumentargument{OEM}}{fiee}} 
>>
>> \doifelsedocumentargument{OEM}
>>    {\def\OEM{\getdocumentargument{OEM}}}
>>    {\def\OEM{fiee}}
>>
>> or
>>
>> \def\OEM
>>    {\ifempty{\getdocumentargument{OEM}}%
>>       fiee%
>>     \else
>>       \getdocumentargument{OEM}%
>>     \fi}
> 
> Thank you, both works (of course, if you say so…).
> Also in my actual project.
> 
> Can you explain why
> \define\OEM{\doifelsedocumentargument{OEM}{\getdocumentargument{OEM}}{fiee}} 
> 
> doesn’t?

1. \define creates an unexpandable command which can't be used as name 
placeholder for \color.

%%%% begin example
\starttext

\protected\def\GELB{yellow} % \defineexpandable\GELB{...}
           \def\BLAU{blue}   %           \define\BLAU{...}

\color[\GELB]{yellow}

\color[\BLAU]{blue}

\stoptext
%%%% end example

2. The \doifelsedocumentargument command is not expandable as well which 
makes it impossible to use it to pick the correct color name within the 
argument of \color.

Wolfgang
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