Can local variables (including parameters) be used in semantic lookahead?
Yes to a point. The problem is that semantic lookahead specifications are evaluated during syntactic lookahead (and during lookahead of more than 1 token). But the subroutine generated to do the syntactic lookahead for a nonterminal will not declare the parameters or the other local variables of the nonterminal. This means that the code to do the semantic lookahead will fail to compile (in this subroutine) if it mentions parameters or other local variables. So if you use local variables in a semantic lookahead specification within the BNF production for a nonterminal n, make sure that n is not used in syntactic lookahead, or in a lookahead of more than 1 token. This is a case of three rights not making a right! It is right that semantic lookahead is evaluated in during syntactic lookahead, it is right (or at least useful) that local variables can be mentioned in semantic lookahead, and it is right that local variables do not exist during syntactic lookahead. Yet putting these three fea
