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I want to pass an argument string to \NewDocumentCommand that allows me to apply different code expressions based on the specified option.

For instance, consider a command named product with an argument called type , where the latter can be either "direct" (in such case printing $#2 \times #3$) or "tensor" (in such printing $#2 \otimes #3$).

Karl
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    Welcome! Can you please provide a minimal but complete example people can compile to help you? I don't understand what you mean by 'an argument called type'. Do you just want \NewDocumentCommand {mmm} and then test if #1 is direct or tensor? – cfr Oct 17 '23 at 01:31

2 Answers2

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You can use the xstring package to do such conditions:

The \Product defined below takes an option for parameter (defaults to "direct" if not specified. You need to decide how to handle the error condition.

enter image description here

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{xstring}

\NewDocumentCommand{\Product}{O{direct} m m}{%
    \IfStrEqCase{#1}{%
        {direct}{#2 \times  #3}%
        {tensor}{#2 \otimes #3}%
    }[%
        \text{Unsupported case: #1.}%
    ]%
}


\begin{document}
$\Product{a}{b}$


$\Product[direct]{a}{b}$


$\Product[tensor]{a}{b}$


$\Product[wacky]{a}{b}$
\end{document}
Peter Grill
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The best option is to use l3 layer for this. texdoc interface3 to get the user guide.

Here is an example.

\documentclass{article}

\begin{document}
\ExplSyntaxOn
\cs_new:Npn \l_my_command:n #1
  {


\tl_set:Nn \l_tmpa_tl{#1}
\str_case_e:nnTF {\l_tmpa_tl}  
{

           { none       } {               } 
           { rmfamily   } {  \rmfamily    } 
           { serif      } {   \rmfamily   } 
           { sans-serif } {  \sffamily    } 
           { sans       } {  \sffamily    }
           { sffamily   } {  \sffamily    }
           { ttfamily   } {  \ttfamily    } 

           { mono       } {  \ttfamily    } 



}

               {  TRUE~                            }
               {  FALSE~                           }


}


\l_my_command:n {mono    }  some~text\par


\l_my_command:n {rmfamily}   some~text


\NewDocumentCommand{\MyCommand}{ m }
{
    \l_my_command:n{#1}

}

\ExplSyntaxOff


\MyCommand{mono}  Some other text


\end{document}
yannisl
  • 117,160