Check options in \newcommand or \NewDocumentCommand?

Question

I'm trying to implement a custom command that is called like this:

\mycommand[hello][world]{mandatory1}{mandatory2}

OR:

\mycommand[hello,world]{mandatory1}{mandatory2}

However, I can't figure out how one can check the value of the two options - I want to check if they are really "hello" and "world" and nothing else, not "x" and "y", etc.

The pseudocode would look something like this:

 \NewDocumentCommand{o o m m}{
    if(#1 == "hello"){...} else {...}
    if(#2 == "world"){...} else {...}
}

How can I do this? I already found \IfValueTF{...} in xparse, but I can't check the value of an option with that - only if it was given or not.

Answer 1

Thanks to the comments to my original question I was able to figure out a solution to my problem. However, I'm not sure if it is really appropriate. It works, but maybe there is a better solution?

\NewDocumentCommand\mycommand{o o m m}{
    \ifthenelse{\equal{#1}{hello}}
        {hello}
        {not hello}
    \ifthenelse{\equal{#2}{world}}
        {world}
        {not world}
}

Answer 2

I use a similar command using xparse for setting languages:

\DeclareRobustCommand{\setlanguage}[1]{%
    \IfEq{#1}{da}{%
         \renewcommand{\contentsname}{Indhold} % TOC Name
         }%
         {}% if not, then do this
}%

In the document, you would use:

\setlanguage{da} % or some other ISO 639-1 code

Also see

• https://tex.stackexchange.com/a/33753/13552