Re: [Boost-users] [spirit/qi] Error handler not called

Subject: Re: [Boost-users] [spirit/qi] Error handler not called
From: TONGARI (tongari95_at_[hidden])
Date: 2013-01-26 23:24:41

2013/1/27 Szymon Gatner <szymon.gatner_at_[hidden]>

> Hi,
>
> I am trying to develop a JSON parser using spirit/qi so far it is not
> going bad but I am having serious problem with on_error and error
> handler. This is my code:
>
> namespace qi = boost::spirit::qi;
>   namespace ascii = boost::spirit::ascii;
>   namespace phoenix = boost::phoenix;
>
>   template <typename Iterator>
>   struct error_handler
>   {
>     template <typename, typename, typename, typename>
>     struct result
>     {
>       typedef void type;
>     };
>
>     void operator()(Iterator first, Iterator last, Iterator err_pos,
> const boost::spirit::info& info) const
>     {
>       std::cout << "never called";
>     }
>   };
>
>   template <class Iterator>
>   struct JsonGrammar : public qi::grammar<Iterator, Value(),
> ascii::space_type>
>   {
>     JsonGrammar() : JsonGrammar::base_type(json, "json"),
> error(error_handler<Iterator>())
>     {
>       using qi::double_;
>       using qi::lexeme;
>       using qi::char_;
>       using qi::int_;
>       using qi::on_error;
>       using qi::fail;
>       using phoenix::construct;
>       using phoenix::val;
>       using namespace qi::labels;
>
>       qi::on_error<qi::fail>(json, error(_1, _2, _3, _4));
>
>       string %= lexeme['"' >> +(char_ - '"') >> '"'];
>       number  = int_;
>       member  = string >> ':' >> value;
>       array   = '[' >> value % ',' >> ']';
>       object  = '{' >> member >> *(',' >> member) >> '}';
>       value   = array | object | number | string | qi::bool_ | "null";
>       json    = array | object;
>
>       json.name("json");
>
>
>     }
>
>     phoenix::function<error_handler<Iterator> > const error;
>     qi::rule<Iterator, std::string(), ascii::space_type> string;
>     qi::rule<Iterator, int(), ascii::space_type> number;
>     qi::rule<Iterator, Value(), ascii::space_type> json;
>     qi::rule<Iterator, Array(), ascii::space_type> array;
>     qi::rule<Iterator, Value(), ascii::space_type> value;
>     qi::rule<Iterator, Object(), ascii::space_type> object;
>     qi::rule<Iterator, std::pair<std::string, Value>(),
> ascii::space_type> member;
>   };
>
> now when i try to parse
>
> std::string json = "[1, 2, 3, 4, t]";
>
> parising result is false. but error handelr is never called. What am I
> doing wrong?
>

You're not using expectation point (i.e.  ">"), so no error would be
triggered.