[Tex/LaTex] Mutually exclusive options in packages

Question

Is there a standard way to define mutually exclusive options in a package?

Could someone provide a simple example?

Currently I am mostly intrested in LaTeX2e but it would be nice to see a LaTeX3 implementation also.

Answer 1

The kvoptions package, which provides key-value type options, also has the possibility to define complementary options:

\DeclareBoolOption{draft}
\DeclareComplementaryOption{final}{draft}

This generates an if-switch which is set to true by draft but to false by final.

---

If you however mean otherwise mutually exclusive options, e.g. three options where only one can be used, then you best define three if-switches which are set to true by its corresponding option. The options then either set the if-switches of the other options to false or raise an error or warning if one of these if-switches are already set to true.

% package 'foo'
% Example: three mutually options alpha, beta, gamma; last one 
\newif\iffoo@alpha
\newif\iffoo@beta
\newif\iffoo@gamma

\DeclareOption{alpha}{\foo@alphatrue\foo@betafalse\foo@gammafalse}
\DeclareOption{beta}{\foo@alphafalse\foo@betatrue\foo@gammafalse}
\DeclareOption{gamma}{\foo@alphafalse\foo@betafalse\foo@gammatrue}

\ProcessOptions*% process options it the order the user provides them

% package body:
\iffoo@alpha
   % alpha code
\fi
\iffoo@beta
   % beta code
\fi
\iffoo@gamma
   % gamma code
\fi

or with error messages:

\def\foo@mutopterr{%
    \PackageError{foo}{Options 'alpha', 'beta' and 'gamma' are mutually exclusive.}{}%
}%
\DeclareOption{alpha}{%
    \iffoo@beta\foo@mutopterr\fi
    \iffoo@gamma\foo@mutopterr\fi
    \foo@alphatrue\foo@betafalse\foo@gammafalse
}
\DeclareOption{beta}{%
    \iffoo@alpha\foo@mutopterr\fi
    \iffoo@gamma\foo@mutopterr\fi
    \foo@alphafalse\foo@betatrue\foo@gammafalse
}
\DeclareOption{gamma}{%
    \iffoo@alpha\foo@mutopterr\fi
    \iffoo@beta\foo@mutopterr\fi
    \foo@alphafalse\foo@betafalse\foo@gammatrue
}