Re: %union and shared pointers to AST nodes

[Evan Lavelle]

Frans Englich wrote:
> On Friday 16 September 2005 20:28, Evan Lavelle wrote:
>
> > struct yystype {
> >    ...
> >    antlr::RefToken  tok;
> >    antlr::RefAST    ast;
> > };
> >
> > #define YYSTYPE yystype
>
>
> Yupp, that is an attractive solution from a memory management perspective. 
> However, I have trouble with connecting flex to that. This is my type:
> mType struct is included into the XPathLexer so the compiler sees it. 
> ...
> It feels as if I've gotten something dead wrong, but in a nutshell: how do I 
> integrate with flex when using a YYSTYPE that is a struct?

What is XPathlval? Is it yylval? If so, 'XPathlval.string = x' should 
work fine.

The code above is in a .h file which I include in the C section of 
*both* the lex and parser files; I think that'll fix your problem. If 
not, check your generated lex.yy.c - it should be pretty easy to find 
out how to make it compile.

> (From the top of my head it would be nice if one could combine different types 
> for different types of "entities". Say, a union for tokens, and an YYSTYPE 
> struct for non-terminals.

I personally don't see any advantage in the yystype/union/struct 
mechanism; I would prefer to see a clean token interface between flex 
and bison, which is completely independent of bison's $/typing mechanism 
(which flex needs to know nothing about).

Evan