lhs2TeX and Syntax conflicting on <> characters

Question

I'd like to use Syntax and lhs2TeX together, but Syntax's usage of <> in production rule names seems to conflict with lhs2TeX:

\documentclass{article}
\usepackage[nounderscore]{syntax}

%include lhs2TeX.fmt

\begin{document}
\begin{grammar}
<foo> ::= <bar>
\end{grammar}
\end{document}

if I try to typeset this:

$ lhs2TeX a.lhs -o a.tex
$ pdflatex a.tex

I get

! Use of \gr@implitem doesn't match its definition.
l.97 ...n{grammar}\begingroup\par\noindent\advance
                                                  \leftskip\mathindent\(

Is there a way to use these two packages together?

Answer 1

Leading < characters are interpreted by lhs2TeX as shorthand for the spec environment (i.e. literate Haskell that should not be picked up by the compiler), as explained in chapter 3 of its usage guide. I was able to work around this by simply adding a leading space before the < on the production rule's left-hand side:

\documentclass{article}
\usepackage[nounderscore]{syntax}

%include lhs2TeX.fmt

\begin{document}
\begin{grammar}
 <foo> ::= <bar>
\end{grammar}
\end{document}

This version is processed by lhs2TeX and pdflatex as expected.