On 2024-10-16 17:48, Wolfgang Schuster wrote:
> Rik Kabel schrieb am 16.10.2024 um 23:18:
>> <stuff deleted for brevity in replying.>
>
> When you have argument after square brackets you have to use #: to 
> continues scanning for arguments of the command. For the mandatory 
> argument you should just use #2 and keep #= for the optional arguments 
> which are only used when text enclosed in curly braces appears. The #* 
> between the third and fourth argument allows spaces between them.
>
> %%%% begin example
> \tolerant\protected\def\Bi[#1]#:#2#*#=#*#=%
>   {(1=#1)%
>    (2=#2)%
>    (3=#3)%
>    (4=#4)}
>
> \starttext
>
> [\Bi[one]{two}{three}{four}]
>
> [\Bi [one] {two} {three} {four}]
>
> [\Bi [one] {two} {three}]
>
> [\Bi [one] {two}]
>
> [\Bi {two}]
>
> [\Bi [one] {two}]
>
> \stoptext
> %%%% end example
>
> To check whether a argument is empty or not you can use the 
> \ifparameter command with the parameter to check (i.e. #1) as argument 
> (don't forget the \or) but \doifempty etc. work as well.
>
> %%%% begin example
> \tolerant\protected\def\Bi[#1]#:#2#*#=#*#=%
>   {\ifparameter#1\or
>      First argument is used.
>    \else
>      First argument is missing or empty.
>    \fi}
>
> \starttext
>
> \Bi {bar}
>
> \Bi [] {bar}
>
> \Bi [foo] {bar}
>
> \stoptext
> %%%% end example
>
> Wolfgang
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Excellent, and thank you for the explanation. I guess #? is still available.

(I had tried with #:, but not in combination with [#1] and #= for the 
last parameter).

-- 
Rik