Am 06.11.2013 um 20:26 schrieb Pablo Rodriguez <oi...@gmx.es>:
> Dear list,
>
> I’m trying to define a command that has a conditional argument:
>
> \def\MyCommand#1#2#3{#1, #2, \doifemptyelse{#3}{#1}{#3}}
> \starttext
> \MyCommand{first}{second}
> \stoptext
>
> The problem is that \doifemtpyelse only works if there the third
> argument is there as {}. And the third argument is actually an exception
> to workaround an unwanted behavior of the command in very few
> exceptional cases.
>
> Is there no way to make \MyCommand above work with \doifemptyelse even
> if its third argument is not defined?
\def\MyCommand
{\dotriplegroupempty\doMyCommand}
\def\doMyCommand#1#2#3%
{#1, #2, \ifthirdargument #3\else #1\fi}
\starttext
\MyCommand{first}{second}{third}
\MyCommand{first}{second}
\stoptext
Wolfgang
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