Boost.Spirit X3: How to Use position_tagged for Parsing Position Information

To use 'boost::spirit::x3::position_tagged', you need to follow these steps:

1. Include the necessary headers:

#include <boost/spirit/home/x3.hpp>

2. Define a struct that will hold the position information, typically called 'position_tagged'.

struct position_tagged
{
    std::size_t line;
    std::size_t column;
};

3. Use 'boost::spirit::x3::position_tagged' as a base class for your parser grammar and define the 'position' member function to retrieve the position information.

struct my_parser : boost::spirit::x3::position_tagged
{
    // ...

    template <typename Iterator, typename Context>
    boost::spirit::x3::position_tagged position(Iterator const& first, Iterator const& last, Context const& context)
    {
        return boost::spirit::x3::position_tagged{boost::spirit::x3::get_line(first), boost::spirit::x3::get_column(first)};
    }
};

4. Use the 'position_tagged' struct to define your grammar rules as needed. For example:

auto my_rule = boost::spirit::x3::rule<my_parser, std::string>{'my_rule'} = boost::spirit::x3::lit('hello') >> boost::spirit::x3::lit('world');

5. Parse your input using the 'parse' function and provide an instance of your parser as the first argument. The position information will be automatically stored in the 'position_tagged' struct.

my_parser parser;
std::string input = 'hello world';
std::string::const_iterator begin = input.begin();
std::string::const_iterator end = input.end();
bool success = boost::spirit::x3::parse(begin, end, parser);

6. After parsing, you can access the position information using the 'line' and 'column' members of the 'position_tagged' struct.

std::cout << 'Line: ' << parser.line << ', Column: ' << parser.column << std::endl;

Note that the example provided here is a basic usage example and may not cover all use cases. You may need to adapt it to your specific requirements.