Ggtkuk

How may I define a new command that admits starred and non-starred variants, and that also admits an optional argument?

I tried the following:

documentclass{minimal}

makeatletter

newcommandMyCommand[1][1]{%

  @ifstar{%

    The starred variant with parameter: #1%

  }{%

    The non-starred variant with parameter: #1%

  }

}

makeatother

begin{document}

MyCommand    \    

MyCommand*   \

MyCommand[2] \

MyCommand*[2]

end{document}

But this gives:

The non-starred variant with parameter: 1

The starred variant with parameter: 1

The non-starred variant with parameter: 2

The starred variant with parameter: 1[2]

Yet, one can write MyCommand[2]* to obtain "The starred variant with parameter: 2" but somehow I'd like the above version to work.

With xparse it's very easy to play around with optional arguments and starred variants:

documentclass{article}

usepackage{xparse}

NewDocumentCommandMyCommand

  {

    s % optional *

    O{1} % first optional argument (default = 1)

  }

  {%

    IfBooleanTF{#1}

      {The starred variant with parameter: #2}

      {The non-starred variant with parameter: #2}

  }

begin{document}

noindent

MyCommand   \

MyCommand*  \

MyCommand[2]\

MyCommand*[2]

end{document}

With LaTeX's newcommand it a little trickier. The @ifstar macro looks at the next token after the macro is expanded and has absorbed its arguments, so you need to first check for the * and only then look for the optional argument:

documentclass{article}

makeatletter

newcommandMyCommand

  {%

    @ifstar

      {MyCommand@star}

      {MyCommand@nostar}%

  }

newcommandMyCommand@star[1][1]{%

  The starred variant with parameter: #1%

}

newcommandMyCommand@nostar[1][1]{%

  The non-starred variant with parameter: #1%

}

makeatother

begin{document}

noindent

MyCommand   \

MyCommand*  \

MyCommand[2]\

MyCommand*[2]

end{document}

Both versions print:

Your code works, but not as you expect it to. The MyCommand[1][1] looks for an optional argument “while expanding” MyCommand, which then gives you:

@ifstar{%

  The starred variant with parameter: <optional argument or default>%

}{%

  The non-starred variant with parameter: <optional argument or default>%

}

and only after that the @ifstar test will be expanded to look for the optional * and choose the text accordingly, so the actual syntax for the command you defined is:

MyCommand[optional argument]<optional star>

Make MyCommand take no parameters, but just figure out the star. Then fork from there.

documentclass{minimal}

makeatletter

newcommandMyCommand{%

  @ifstar{mycommandstar}{mycommandnostar}

}

newcommandmycommandstar[1][1]{The starred variant with parameter: #1}

newcommandmycommandnostar[1][1]{The non-starred variant with parameter: #1}

makeatother

begin{document}

MyCommand    \    

MyCommand*   \

MyCommand[2] \

MyCommand*[2]

end{document}