Re: [boost] spirit: Using actions on rules with more precision

From: John Ky (newhoggy_at_[hidden])
Date: 2006-01-23 22:13:24

Hi Hartmut,

Thanks for the help.

I got it to work with an extra ::context_t in:

   typedef rule<strlit_closure::context_t> rule_type;

Is that the correct way to do it?

Also, I have another problem:

The rule:

  rule_string mystringrule;
  mystringrule =
    * ( confix_p('"', (*c_escape_ch_p)[mystringrule.val +=
construct_<string>(arg1, arg2)], "')
      );

Will match:

  "hello""world"

as:

  helloworld

But the rule:

  rule_string mystringrule;
  mystringrule =
    * ( confix_p('"', (*c_escape_ch_p)[mystringrule.val +=
construct_<string>(arg1, arg2)], "')
      | (anychar_p - '"')      /* this line added */
      );

matched returning an empty string.

-John

On 1/24/06, Hartmut Kaiser <hartmut.kaiser_at_[hidden]> wrote:
> John Ky wrote:
>
> > Is it possible to define a rule:
> >
> >     rule<> mystringrule = confix_p('"', *c_escape_ch_p, '"')
> >
> > differently such that I can use
> >
> >     std::string value;
> >
> >     bool result = parse("\"hello world\"",
> > mystringrule[assign_a(value)]).full;
> >
> > and get the text = "hello world" assigned to value?
> >
> > Currently, I get text = "\"hello world\"" instead.  ie with
> > double quotes at either end.
>
> I'ld suggest to use closures for that (not tested):
>
>     struct strlit_closure
>     : public boost::spirit::closure<strlit_closure, std::string>
>     {
>         member1 val;
>     };
>
>     typedef rule<strlit_closure> rule_type;
>
>     rule_type mystringrule
>         = confix_p('"', *c_escape_ch_p[assign_a(mystringrule.val)], '"');
>
>     bool result = parse("\"hello world\"",
>         mystringrule[assign_a(value)]).full;
>
> This is based on the fact, that the first closure member of a rule is used
> as the rule's value.
>
> HTH
> Regards Hartmut