Lets look at boost::spirit.
Lets say that I want to throw a boost::spirit parsing exception.
Information available to me includes:
1) the filename 2) line number of error 3) charactar postion of the error
Here is how I propose that we throw the error.
struct tag_file_name: boost::error_info_value<std::string> { }; struct tag_line_number: boost::error_info_value<std::string> { }; struct tag_charactar_position : boost::error_info_value<std::string> { };
typedef boost::error_info_group< tag_file_name, tag_line_number, tag_charactar_position> spirit_parsing_error_t;
int size; std::string path; boost::spirit::parse_info<char const*> info = boost::spirit::parse(def.c_str(), face_grammar(path,size)); if (!info.full) throw my_error() << spirit_parsing_error_t( path, info.line, info.postition);
If all parsing exceptions contain a file name, line number, and character position, wouldn't it make sense to group them in a struct: struct spirit_parsing_context { spirit_parsing_context( std::string file_name, int line, size_t position ): file_name(file_name), line(line), position(position) { } std::string file_name; int line; size_t position; }; And then you can do: throw my_error() << error_info<tag_spirit_parsing_context>( spirit_parsing_context(path, info.line, info.position)); I am not familiar with boost::spirit, but I would think that if it commonly reports parsing errors that have all this information, then spirit_parsing_context should be part of the library anyway; thus, all you'd have to do is define the tag type: struct tag_spirit_parsing_context: error_info_value<spirit_parsing_context> { }; Then you'd do: throw my_error() << error_info<tag_spirit_parsing_context>(spc); where "spc" is the object of type spirit_parsing_context that spirit itself returned when the failure was reported. Emil Dotchevski