# breqn and \brace

I was looking forward to using breqn, but it mysteriously fails with the following piece of code:

\begin{dmath*}
{2 \brace 3}
\end{dmath*}


However, this construct outputs a "Missing delimiter" error (\choose works without a hitch). What gives?

I'm working with TexLive 2011 on OS X.

• Welcome to TeX.SE. It is always best to compose a fully compilable MWE that illustrates the problem including the \documentclass and the appropriate packages so that those trying to help don't have to recreate it. – Peter Grill Mar 15 '12 at 1:25

\{ has additional code so that it works in text mode as well as math and that upsets breqn in the form used here. These infix primitives are rightly deprecated with amsmath, but if you must you may:-)

\documentclass{article}

\let\oldlbrace\lbrace
\let\oldrbrace\rbrace
\def\brace{\atopwithdelims\oldlbrace\oldrbrace}
\usepackage{breqn}

\begin{document}
\begin{dmath*}
{2 \brace 3 }
\end{dmath*}
\end{document}