-% |\grammarlabel| command. The command is given two arguments: the name of
-% the nonterminal (which was enclosed in angle brackets), and the `production
-% operator'. The command is expected to produce the label. By default, it
-% typesets the nonterminal name using |\synt| and the operator at opposite
-% ends of the label, separated by an |\hfill|.
+% |\grammarlabelx| command. The command is given three arguments: the name
+% of the nonterminal (which was enclosed in angle brackets), the following
+% decorative material, and the `production operator'. The command is
+% expected to produce the label. By default, it typesets the nonterminal
+% name using |\synt| followed by the decoration, and the operator, at
+% opposite ends of the label, separated by an |\hfill|.
+%
+% \DescribeMacro\grammarlabel
+% For compatibility, if there is no decorative material, the macro
+% |\grammarlabel| is called instead, with just two arguments: the nonterminal
+% name and the operator. The default implementation of |\grammarlabel| just
+% calls |\grammarlabelx| with empty decoration.