Am 23.04.2025 um 17:33 schrieb G.C.H.M. Verhaag via ntg-context:
Hi ConTeXt users,
I'm trying to build a user-defined command called *mycommand* and
followed the hints on (https://wiki.contextgarden.net/
ConTeXt_and_Lua_programming/Tutorials/System_Macros/Handling_Arguments)
\def\dodefinemycommand[#1][#2]% {\getparameters[\??xx#1][#2]}
\def\mycommand%
{\dodoubleargumentwithset\dodefinemycommand\strut\blank[2*big] See what
happens: \@@xxonex}
and call it with:
*\mycommand[one,two][x=1,y=2]*
**
This yields a fatal error; while I'd expect something like:
*See what happens: 1*
What am I doing wrong here?
You can't use ? or @ as part of command names unless you use \unprotect
.. \protect when you create and access them. In the following example
the first \@@test command which is placed in the protect works as
expected but the second fails because TeX treats only \@ as command
(which doesn't exists and results in an error) and everything afterwads
(i.e. @test) is simple text.
%%%% begin example
\starttext
\unprotect
\def\@@test{[test]}
A\@@test B
\protect
A\@@test B
\stoptext
%%%% end example
Below is a simple definition of \mycommand which uses the old method to
create optional arguments. There are better ways to achieve the same
result with newer ConTeXt versions but you didn't provide enough
information about your goal.
%%%% begin example
\starttext
\protected\def\mycommand
{\dodoubleargument\domycommand}
\def\domycommand[#1][#2]%
{\def\dodomycommand##1{\getparameters[mycommand##1][#2]}%
\processcommalist[#1]\dodomycommand
%
See what happens: \getvalue{mycommandonex}}
\mycommand[one,two][x=1,y=2]
\stoptext
%%%% end example
Wolfgang
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