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amsmath: cases and \arraystretch

The amsmath cases environment is using the array environment internally, like its matrix environments. If you want to change the interline spacing of matrices you could redefine \arraystretch, like for any array environment. But it won’t work for cases – amsmath defines an arraystretch value of 1.2 internally.

A solution is to redefine the \env@cases macro. Here’s a redefinition, introducing an optional parameter controlling the spacing:

\makeatletter
\renewcommand*\env@cases[1][1.2]{%
  \let\@ifnextchar\new@ifnextchar
  \left\lbrace
  \def\arraystretch{#1}%
  \array{@{}l@{\quad}l@{}}%
}
\makeatother

Now by \begin{cases} … \end{cases} the default value of 1.2 will be used, but by using the optional parameter like \begin{cases}[0.8] … \end{cases} the spacing will be adjusted accordingly.

This topic was discussed on mrunix.de.

24. September 2008 by stefan
Categories: Mathematics | 6 comments