Bison: Optional tokens in a single rule.
- by Simone Margaritelli
Hi there .. i'm using GNU Bison 2.4.2 to write a grammar for a new language i'm working on and i have a question.
When i specify a rule, let's say :
statement : T_CLASS T_IDENT '{' T_CLASS_MEMBERS '}' {
// create a node for the statement ...
}
If i have a variation on the rule, for instance
statement : T_CLASS T_IDENT T_EXTENDS T_IDENT_LIST '{' T_CLASS_MEMBERS '}' {
// create a node for the statement ...
}
Where (from flex scanner rules) :
"class" return T_CLASS;
"extends" return T_EXTENDS;
[a-zA-Z\_][a-zA-Z0-9\_]* return T_IDENT;
(and T_IDENT_LIST is a rule for comma separated identifiers).
Is there any way to specify all of this only in one rule, setting somehow the "T_EXTENDS T_IDENT_LIST" as optional?
I've already tried with
T_CLASS T_IDENT (T_EXTENDS T_IDENT_LIST)? '{' T_CLASS_MEMBERS '}' {
// create a node for the statement ...
}
But Bison gave me an error.
Thanks
