Re: [Boost-users] [Spirit] Incompatible skipper type?

Subject: Re: [Boost-users] [Spirit] Incompatible skipper type?
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2019-01-10 21:22:41

On Thu, Jan 10, 2019 at 4:21 PM Michael Powell <mwpowellhtx_at_[hidden]> wrote:
>
> Hello,

I should also mention, I am using the latest Boost 1.69.0.

> I'm a bit confused here, not sure what this means:
>
> Severity Code Description Project File Line Suppression State
> Error C2664 'bool boost::function4<R,T0,T1,T2,T3>::operator
> ()(T0,T1,T2,T3) const': cannot convert argument 4 from 'const Skipper'
> to 'T3' Kingdom.Json.Parser.Tests
> d:\dev\boost.org\boost_1_69_0\boost\spirit\home\qi\nonterminal\rule.hpp
> 304
>
> // If you are seeing a compilation error here stating that the
> // fourth parameter can't be converted to a required target type
> // then you are probably trying to use a rule or a grammar with
> // an incompatible skipper type.
> if (f(first, last, context, skipper)) {}
>
> Incompatible where? How? Requires clarification please. The default
> Skipper type, which I am using at the moment, is
> boost::spirit::qi::space_type. I aim to use the proven Comment Skipper
> that I leveraged in a previous iteration eventually, but I expect that
> compilation should work with the simple space type at least.
>
> Because as far as I can determine all of the rules in my Grammar have
> the same Skipper type.
>
> struct json_grammar : qi::grammar<It, value_t(), Skipper> {
>     using iterator_type = It;
>     using skipper_type = Skipper;
>     using char_rule_type = qi::rule<It, char()>;
>     json_grammar() : json_grammar::base_type(value_) {
>         // ...
>      }
> private:
>     struct escapes_t : qi::symbols<char, char> {
>         escapes_t() {
>             this->add("\\b", '\b')
>                 ("\\f", '\f')
>                 ("\\n", '\n')
>                 ("\\r", '\r')
>                 ("\\t", '\t')
>                 ("\\v", '\v')
>                 ("\\\\", '\\')
>                 ("\\/", '/')
>                 ("\\'", '\'')
>                 ("\\\"", '"')
>                 ;
>         }
>     } char_esc;
>
>     //qi::rule<iterator_type> line_cont;
>     char_rule_type hex_esc, unicode_esc;
>     qi::rule<iterator_type, str_t()> quot_str, tick_str, str_lit;
>
>     qi::rule<iterator_type, std::vector<value_t>(), skipper_type> array_;
>     qi::rule<iterator_type, boost::tuple<key_t, value_t>(),
> skipper_type> member;
>     qi::rule<iterator_type, std::vector<boost::tuple<key_t,
> value_t>>(), skipper_type> object_;
>
>     qi::rule<iterator_type, key_t(), skipper_type> member_key;
>     qi::rule<iterator_type, value_t(), skipper_type> value_;
>
>     qi::rule<iterator_type, numeric_sign_t(), skipper_type> numeric_sign;
>     qi::rule<iterator_type, float_t(), skipper_type> float_lit;
>     qi::rule<iterator_type, floating_point_number_t(), skipper_type>
> floating_point;
>     qi::rule<iterator_type, int_t(), skipper_type> hex_int, oct_int,
> dec_int, int_lit;
>     qi::rule<iterator_type, integer_number_t(), skipper_type> integer;
>
>     qi::rule<iterator_type, boolean_t(), skipper_type> bool_lit;
>     qi::rule<iterator_type, null_t(), skipper_type> null_lit;
> };
>
> Best regards,
>
> Michael Powell