RE: [boost] Spirit Question

From: Hartmut Kaiser (hartmutkaiser_at_[hidden])
Date: 2003-08-21 14:07:27

Paul Hamilton wrote:

> I want to parse "," separated lists of strings.
> 
> I have:
> 
>      char const*                 plist_wo_item = "x, y, z";
>      rule<>                      list_wo_item;
>      std::vector<std::string>    vec_list;
> 
>      list_wo_item =
>              (*anychar_p) >> *( ',' >> 
> (*anychar_p)[append (vec_list)])
>          ;
> 
>      parse_info<> result = parse (plist_wo_item, list_wo_item);
>      if (!result.hit)
>      	return false;
> 
> This only places 1 item into vec_list.

The first *anychar_p eats up all your input (it matches zero or more
occurences of any char :-). There are several ways to circumvent this
problem:

    list_wo_item = (*(anychar_p - ','))[append (vec_list)]
        >> *( ',' >> (*(anychar_p - ','))[append (vec_list)] )
        ;

which is very verbose but functional. 
To simplify the expression, try this:

    list_wo_item = list_p((*anychar_p)[append(vec_list)], ',');

which does the required refactorings (parser transformations) behind the
scene.

BTW, to skip the whitespace in between the list items, you may want to
use a skip parser while calling the parse function:

    parse_info<> result = parse (plist_wo_item, list_wo_item, space_p);

HTH
Regards Hartmut