and the variables may also appear on the right-hand side
in place of a nonterminal.
Such a rule stands for a family of rules,
-in each variable is replaced by
+in which each variable is replaced by
each possible simple nonterminal or terminal symbol.
.PP
The letter \*e denotes the empty nonterminal
|
.I identifier
.|
+.B <
+.I plain-type
+.B >
+.|
.B ?
.I s-expression
.|