Re: [Boost-users] Spirit: skip parser and rules

From: Joel de Guzman (joel_at_[hidden])
Date: 2008-07-21 09:22:23

Alessandro Re wrote:
> Hello,
> I've this code:
> 
> // w and space_signaler are a function objects which print out some info.
> bool read_str(const char *in, StrList &w) {
> 	rule<> identifier = +alnum_p;
> 	rule<> statement = identifier[w] >> ch_p(';')[w];
> 
> 	return parse(
> 		in,
> 		(statement)[w],
> 		space_p[space_signaler] // Called for initial spaces only
> 	).full;
> }
> 
> Well, I don't understand why if i use (statement)[w] where signaled,
> the space_signaler is never called for non-initial spaces, while if i
> write directly the rule, it does correctly:
> 
> 	return parse(
> 		in,
> 		(identifier[w] >> ch_p(';')[w])[w],
> 		space_p[space_signaler] // Called for every space
> 	).full;
> 
> In the latter case, it parses (skipping spaces) inputs like:
> "hello;"
> "hello    ;"
>  "    hello    ; "
> while in the former it parses correctly inputs like
> "   hello;"
> "hello;"
> disallowing spaces between the word and the semicolon.
> 
> Can someone explain me why does this happens?

The proper Spirit forum is:
https://lists.sourceforge.net/lists/listinfo/spirit-general

Anyway, I am surprised this compiled at all. You have the wrong
rule type. I suggest not using bare rules this way. Use a
grammar instead. Please post to the Spirit mailing list for
follow ups. Thanks!

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://spirit.sf.net