lineno and syntax package incompatibilities

Question

I'm using the syntax package from the mdwtools version 1996/05/17 1.07. I successfully set the properties to show a grammar definition properly but then when I try to combine it with the lineno package I got a nasty error showing a double line number for each new rule. Then digging the code of syntax.sty I found I can fix the problem in the definition of 'grammar' commenting this line:

\vskip-\baselineskip%

Now it works better but I have extra new lines between rules. In fact the definitions start at line number 2 and I cannot remove these extra lines! (It seems is related to the lists command) I suppose this is a bug. TeX is far out from my expertize so I report this bug wondering if someone have a workaround or help me to fix this issue.

Answer 1

Here's a solution:

\documentclass{article}
\usepackage{syntax}
\usepackage{lineno}

\makeatletter
\def\gr@implitem<#1> #2 {%
 \sbox\z@{\hskip\labelsep\grammarlabel{#1}{#2}}%
  \strut\@@@par% lineno.sty redefines \@@par which was in the original code
 \vspace{-\parskip}%
  \vspace{-\baselineskip}%
  \hrule\@height\z@\@depth\z@\relax%
  \item[\unhbox\z@]%
  \catcode`\<\active%
}
\makeatother
\begin{document}
\begin{linenumbers}
\begin{grammar}

<statement> ::= <ident> ‘=’ <expr> 
\alt ‘for’ <ident> ‘=’ <expr> ‘to’ <expr> ‘do’ <statement> 
\alt ‘{’ <stat-list> ‘}’ 
\alt <empty> 
<stat-list> ::= <statement> ‘;’ <stat-list> | <statement> 

<statement> ::= <ident> ‘=’ <expr> 
\alt ‘for’ <ident> ‘=’ <expr> ‘to’ <expr> ‘do’ <statement> 
\alt ‘{’ <stat-list> ‘}’ 
\alt <empty> 

\end{grammar} 
\end{linenumbers}
\end{document}

Explanation: lineno.sty counts lines based on the \par macro which is internally in LaTeX \@@par. lineno.sty needs to use its own version of that, \@@@par which keeps track of spurious blank lines. Replacing syntax.sty use of \@@par with \@@@par fixes the problem.

Answer 2

Why don't you use one paclage like listings for example ?

\documentclass{article}
    \usepackage{listings}

\begin{document}

\begin{lstlisting}

<statement> ::= <ident> = <expr> 
  |  for <ident> = <expr> to <expr> do <statement> 
  |    <stat-list>
  |  <empty> 
<stat-list> ::= <statement> ; <stat-list> | <statement> 

<statement> ::= <ident> = <expr> 
  |  for <ident> = <expr> to <expr> do <statement> 
  |    <stat-list>
  |  <empty> 
\end{lstlisting}

\end{document}