On Thu, 24 May 2018 14:50:36 +0200, Hans Hagen wrote:

On 5/24/2018 11:21 AM, Christoph Reller wrote:

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On Wed, 23 May 2018 16:01:05 +0200, Hans Hagen wrote:

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On 5/23/2018 3:39 PM, Christoph Reller wrote:

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What is the right way to define a command with both mandatory and optional arguments, e.g:

\MyCommand[optional][mandatory]

Consider the following MWE:

\unexpanded\def\MyCommand[#1]{ \dosingleempty{\doMyCommand[#1]}} \def\doMyCommand[#1][#2]{ \doifsomething{#1}{number 1: #1\par} \doifsomething{#2}{number 2: #2}\blank[big]} \starttext \MyCommand[A][B] \MyCommand[A] \stoptext

In last year's versions of ConTeXt the output was

number 1: A number 2: B number 1: A

In the latest version of ConTeXt the output is

number 1: A number 2: B number 2: A

Is this behavior intended? How can I make a definition whose behavior does not change in new versions of ConTeXt?

i'm not sure wht happens at your end but this is the best way:

\unexpanded\def\MyCommand {\dodoubleempty\doMyCommand}

\def\doMyCommand[#1][#2]% {\iffirstargument number 1: #1% \par \fi \ifsecondargument number 2: #2% \fi \blank[big]}

\starttext \MyCommand[A][B] \MyCommand[A] \stoptext

Thank you Hans for this information. My question is rather about error handling. I want:

\MyCommand[A][B] % <- succeeds with #1->A, #2->B \MyCommand[A] % <- succeeds with #1->A \MyCommand % <- fails with "! Use of \MyCommand doesn't match its definition"

I just wanted to ask whether there is a standard way to achieve this with \do<whatever>empty. If not, then this is also okay. just use \dodoubleempty instead

Thank you for your hint, Hans. \dodoubleempty renders both arguments optional and hence the command can be used without any argument, which is not what I intended. Of course I can still test in the command's definition whether at least one argument is given and generate an error myself. In i-context.pdf, many arguments are documented as being optional and I assume that all the others are mandatory. A quick test has, however, shown that when omitting mandatory arguments, either no error is generated (e.g., nothing is setup or defined) or an obscure error emerges other than "! Use of \<command> doesn't match its definition". So I take it as a design decision that reporting missing mandatory arguments as errors is not part of the interface implementation, and that is a perfectly acceptable decision for me. It is just good to know. Thank you all for your highly valued feedback! Cheers, Christoph