%% Intercept grammar typesetting and replace the vertical bar with the
%% maths-font version.
-\let\@@grammar\grammar
-\def\grammar{\def\textbar{\hbox{$|$}}\@@grammar}
+\let\@@syn@shorts\syn@shorts
+\def\syn@shorts{\def\textbar{\hbox{$|$}}\@@syn@shorts}
%% Collect super- and subscripts. (Note that underscores are active for the
%% most part.) When we're done, end maths mode if we entered it