# \wideparen in AMS class

I need a \wideparen symbol in a book prepared with amsbook class. I know about a few packages providing this command but...

• ymath does not work with current version of AMS classes
• MnSymbol, mathabx, fourier - all substitute the default math font and this is not what I need (and what the publisher would allow). I need to keep the standard fonts for everything else, but only add this single symbol.

Any ideas how to do that ?

-
By ymath do you mean yhmath? That package works fine with amsbook for me. –  Ian Thompson Aug 29 '12 at 19:38
Unfortunately, pdflatex goes into an infinite loop after I add yhmath to the package list. I didn't try to find what is the source of the problem, however some comments I spotted on internet suggested an incompatibility between yhmath and AMS classes. –  P.K. Aug 30 '12 at 15:02

here's a not-so-little test file that will illustrate the inclusion of a wide paren (and also a wide check) from the mathx font using amsart. since amsbook is a sibling of amsart, it will work there too. (this is one of the ams internal "how to" files; i didn't edit it for conciseness.)

\documentclass{amsart}
\nofiles
\usepackage{verbatim}

%% code from mathabx.sty and mathabx.dcl
\DeclareFontFamily{U}{mathx}{\hyphenchar\font45}
\DeclareFontShape{U}{mathx}{m}{n}{
<5> <6> <7> <8> <9> <10>
<10.95> <12> <14.4> <17.28> <20.74> <24.88>
mathx10
}{}
\DeclareSymbolFont{mathx}{U}{mathx}{m}{n}
\DeclareFontSubstitution{U}{mathx}{m}{n}
\DeclareMathAccent{\widecheck}{0}{mathx}{"71}
\DeclareMathAccent{\wideparen}{0}{mathx}{"75}

\def\cs#1{\texttt{\char\\#1}}

\begin{document}

A wide check should match a wide hat, but inverted.  Observe that
the forms provided have a maximum width.  Some other wide accents
in \verb|mathx| aren't available otherwise.
\begin{align*}
`