[tex-eplain] Position of optional argument

[Rodolfo Medina]

On Sun, Apr 26, 2009 at 07:16:55PM +0100, Rodolfo Medina wrote:

>> I've been using the eplain \@getoptionalarg and \@optionalarg commands in a
>> certain macro.  It turns out to me that the optional argument must be put
>> *before* the non optional argument.
>>
>> How can I set things - if possible - so to put it after it?


Oleg Katsitadze <olegkat at gmail.com> writes:

> Try this:
>
>     \input eplain
>
>     \makeatletter
>
>     \def\test#1{%
>       \def\test at arg{#1}%
>       \@getoptionalarg\@test
>     }
>
>     \def\@test{%
>       \message{^^JArg: \test at arg}%
>       \message{^^JOptional arg: \@optionalarg}%
>     }
>
>     \makeatother
>
>     \test{text}
>     \test{text}[optional text]
>
>     \bye



If, in the above code, in place of `\@getoptionalarg\@test' I put:

\ifnum0=0
      \@getoptionalarg\@test
\else
\fi


then, strangely, it doesn't seem to work any more.  I can't explain why.  Can
anybody?

Thanks for any help
Rodolfo