third_party/boost/spirit/example/x3/actions.cpp

/*=============================================================================
    Copyright (c) 2001-2015 Joel de Guzman

    Distributed under the Boost Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/home/x3.hpp>

#include <iostream>

// Presented are various ways to attach semantic actions
//  * Using plain function pointer
//  * Using simple function object

namespace client
{
    namespace x3 = boost::spirit::x3;
    using x3::_attr;

    struct print_action
    {
        template <typename Context>
        void operator()(Context const& ctx) const
        {
            std::cout << _attr(ctx) << std::endl;
        }
    };
}

int main()
{
    using boost::spirit::x3::int_;
    using boost::spirit::x3::parse;
    using client::print_action;

    { // example using function object

        char const *first = "{43}", *last = first + std::strlen(first);
        parse(first, last, '{' >> int_[print_action()] >> '}');
    }

    { // example using C++14 lambda

        using boost::spirit::x3::_attr;
        char const *first = "{44}", *last = first + std::strlen(first);
        auto f = [](auto& ctx){ std::cout << _attr(ctx) << std::endl; };
        parse(first, last, '{' >> int_[f] >> '}');
    }

    return 0;
}