[texhax] Defining a command which runs differently based ion input argument

[Philipp Stephani]

Am 28.12.2010 um 12:00 schrieb Uwe Lueck:

> That is much worse with LaTeX's square brackets for optional arguments, as some scholars use square brackets for ellipsis or redactional insertions (I experienced this several times):
> 
>    Title-like\\ % imitating the manuscript's line break and spacing
>    [unreadable] ipsum dolor sit amet

That would be fixed if \@ifnextchar didn't swallow space tokens. Similar problems arise with amsmath:

\documentclass{minimal}
\usepackage{amsmath}
\begin{document}
\begin{equation}
  \begin{aligned}
    [u] = [v]
  \end{aligned}
\end{equation}
\end{document}

That one is fixed by the mathtools package.