equivalent groupings. The symbol name is used in writing grammar rules.
By convention, it should be all lower case.
-Symbol names can contain letters, underscores, period, and (not at the
-beginning) digits and dashes. Dashes in symbol names are a GNU
+Symbol names can contain letters, underscores, periods, dashes, and (not
+at the beginning) digits. Dashes in symbol names are a GNU
extension, incompatible with @acronym{POSIX} Yacc. Terminal symbols
that contain periods or dashes make little sense: since they are not
valid symbols (in most programming languages) they are not exported as