Michael Barr barr at math.mcgill.ca
Fri Oct 29 18:01:49 CEST 2010

My problem is well illustrated by the following file

\documentstyle{article}
\def\bbrack#1{[\![#1]\!]}
\begin{document}
$\bbrack{\widehat c =\widehat d}$
\end{document}

Yes, I could add extra space after the argument, but that is a real
kludge.  My real question is why can't I get the \widehat to actually be
centered over its argument.  As you can see, it starts halfway along the
"d" and ends well to the right.  This is also true of the one on the "c"
so it is not just centering over an ascender.

Michael Barr