Re: Implementing identification on SableCC ASTs

[Etienne Gagnon <etienne.gagnon@uqam.ca>]

Hi Jens,

The usual approach is to build a tree of symbol tables, e.g.:
- 1 outer scope (global variables) symbol table
- 1 symbol table for each inner scope which maintains a pointer
  to its "parent" scope

You usually store a pointer from each block of code to its appropriate
symbol table.

Looking up a symbo goes recursively from the "current" symbol table
to its ancestors until a match is found.

You should look at the JJOOS example compiler (see Prof. Hendren's
cs520 course page http://www.sable.mcgill.ca/~hendren/520/).

Etienne

> > To make your solution work, it would be necessary to
> > define a
> > SymbolTable class that "remembers" everything. I.e.
> > when the so called
> > SemanticAnalyser class goes through the AST and
> > opens scopes, enters
> > identifiers and closes scopes - everything has to be
> > stored in the
> > SymbolTable.
> >
> > Normally, the symbol table "forgets" about
> > identifiers declared in a
> > scope when the scope is closed.
> You are totally right. I had forgotten about the local
> scope variables as well as nested ones. I haven't
> tried the HashMap technique, so I can't really comment
> on that.

--
Etienne M. Gagnon, Ph.D.             http://www.info.uqam.ca/~egagnon/
SableVM:                                       http://www.sablevm.org/
SableCC:                                       http://www.sablecc.org/