[XeTeX] Bug between unicode-math and expex

[James Crippen]

I’m using ExPex (not yet in CTAN, http://www.math.neu.edu/ling/tex/)
for linguistic examples in XeLaTeX and I’ve encountered a bad
interaction between it and unicode-math. Here’s a Minimal Working
Example™:

- - - cut here - - -

\documentclass{article}
\usepackage{fontspec}
\usepackage{unicode-math}
\usepackage{expex}

\begin{document}

\pex
\a
\begingl
	\gla	mea mater sus mala est /
	\glb	my mother pig bad is /
	\glc{‘my mother is a bad pig’}
\endgl
\a
\begingl
	\gla	mea mater sus mala est /
	\glb	wander mother pig apple eats /
	\glc{‘wander, mother, the pig is eating the apples’}
\endgl
\xe

\end{document}

- - -  cut here - - -

To get the correct output, comment out the \usepackage{unicode-math}.
The wrong result is that line breaking fails to occur and the / shows
up in the output.

There is another incorrect output that I am having trouble getting an
MWE to show. In this case the beginning of a multiline example (the
thing started by \begingl) has the characters "><" at the beginning of
the first line. I think this may be something inside of ExPex’s
crossreference tagging (it uses <...> for xref tags) but I haven’t
figured it out.

Can someone who knows unicode-math figure out what is going wrong? I’d
like to be able to use that package but this buggy interaction is
preventing me because I need ExPex more than I do unicode-math.

I am reporting this here because although it’s likely that there is
some assumption in ExPex being violated, I think people who work on
unicode-math are more likely to figure it out than the ExPex
maintainer.

Thanks,
James Crippen