DESCRIPTION

There are two independent topics being discussed here.

(1) Scope of variables. 
(2) typedef variables. 

(1) Scope of variables is solved easily. In your symbol table you have to keep track of the level for all variables. Every time you see a '{' you have to increment the level. So the 'a' will be put into the symbol table as a level 1 variable and the 'b' will be a level 2. The bottom-up quality of LALR will not affect this. The 'a' will be seen first and the 'b' later, so no problem here.

(2) The infamous 'typedef' problem continues to plague the newbie or part-time LALR grammar hacker, but it was solved way back in 1987 by an LALR parser generator which used an integrated symbol table and semantic grammar symbols (e.i. {typedef}). The state-of-the-art simple solution works fine with the LRSTAR parser generator (see http://highperware.com). Here is the simple LALR(1) grammar which solves this 'typedef' problem:

/* C Typedef Solution. */ <error> => error(); <identifier> => lookup(); /* Symbol table lookup. */ /* Rules. */ Input -> [Declaration]... <eof> +> input_ Declaration -> VarDecl [',' Var ]... ';' +> decl_ -> typedef VarDecl2 [',' Var2]... ';' +> typedefdecl_ VarDecl -> Type... Ident Var -> [Ptr]... Ident VarDecl2 -> Type... Ident2 Var2 -> [Ptr]... Ident2 Ident -> <identifier> +> ident_(1) Ident2 -> <identifier> +> ident_(1,{typedef}) Type -> SimpleType +> type_(1) -> Type Ptr Ptr -> '*' +> ptr_ SimpleType -> char -> int -> short -> unsigned -> {typedef}

It handles the input file: typedef unsigned int UINT, * UINTPTR; UNIT a, b, c; UINTPTR x, y, z; Note, no hacks or kludges are required, just a state-of-the-art parser generator. Paul B Mann