I tried using two Environ's in a nested fashion, but I get the
! Argument of \marray has an extra }
error. Any idea why this happens?
\documentclass{minimal}
\usepackage{amsmath,environ}
\NewEnviron{meqmultinum}[1]{
\begin{equation}\begin{split}
\BODY
\end{split}\label{eq:#1}\end{equation}
}
\NewEnviron{marray}[2]{
\renewcommand*{\arraystretch}{#2}
\begin{array}{#1}
\BODY
\end{array}
}
\begin{document}
\begin{meqmultinum}{test}
a&=\begin{marray}{l l}{1.2}
\alpha & \beta\\
\gamma & \kappa
\end{marray}\\
b&=\begin{array}{l l}
\alpha & \beta\\
\gamma & \kappa
\end{array}
\end{meqmultinum}
\end{document}
Best Answer
Environment
split
insidemeqmultinum
provides an alignment. That means that the contents of the environment is processed cell by cell:Cell 1:
a
Cell 2:
=\begin{marray}{l l}{1.2} \alpha
The rest
& \beta \\ \gamma & \kappa \end{marray}
does not belong to cell 2. Thus the code of\begin{marray}
complains, because it cannot find\end
of\end{marray}
.This can be fixed by adding curly braces around
\begin{marray}...\end{marray}
:Why does it work with
array
instead ofmarray
? Environmentarray
does not need to see at the beginning\end{array}
, instead it sets up a tabular and the contents ofarray
with its&
is processed in this inner tabular.Other definition of
marray
Another way to fix this issue is given by David Carlisle in his comment. There is no need for the special environment processing of package
environ
forarray
: