Re: [boost] Re: [ANN] Spirit C++ parser framework

From: George A. Heintzelman (georgeh_at_[hidden])
Date: 2001-05-22 07:51:13

> >         // Generates the parser from the grammar expression
> >         Parser parser = re
> >                       | '(' + re + ')'
> >                       | '(' + re + ',' + im + ')'
> >                       ;
> 
> [snip]
> 
> Consider it done. I'll add that capability or a variation
> into the framework. The open-ended nature of
> spirit makes that trivial to do:
> 
> Something like:
> 
>     FloatVar re, im;
>     Rule<> r = re | '(' >> re >> ')' | '(' >> re >> ',' >> im >> ')';
> 

Careful with your choice of operators for defining rules. First, I 
don't find the '>>' operator as intuitively appealing as the use of '+' 
in the example above. Second, operator precedence rules here would 
group this expression as:

Rule<> r = ( re | '(' ) 
	>> re
	>> ( ')' | '(' )
	>> re
	>> ( ',' 
	>> im
	>> ')' 
        ;

And ')' | '(' is unlikely to give the results you want...

That said, I would love to see something which could robustly handle 
this kind of stuff...

George Heintzelman
georgeh_at_[hidden]