Check if mathversion (font) is defined

Question

One can define a new mathversion using \DeclareMathVersion{sans}.

I wonder if I can test the existence of such a font definition, for example with

\IfMathVersionDefined{sansmath}
  {math font is defined}
  {math font is not defined}

Answer 1

Are you just looking for this?

\makeatletter
\newcommand{\IfMathVersionDefined}[3]{%
  \expandafter\@ifundefined\csname mv@#1\endcsname{#3}{#2}%
}
\makeatother

The above is motivated by the fact that \DeclareMathVersion{#1} defines \mv@#1.

Answer 2

\documentclass{article}

\DeclareMathVersion{blub}


\begin{document}
\ifcsname mv@blub\endcsname
 math version blub exist
\else
 math version blub  doesnt exist
\fi 

\ifcsname mv@bla\endcsname
 math version bla exist
\else
 math version bla doesnt exist
\fi 

\end{document}