third_party/boost/spirit/doc/x3/tutorial/num_list2.qbk

[/==============================================================================
    Copyright (C) 2001-2015 Joel de Guzman
    Copyright (C) 2001-2011 Hartmut Kaiser

    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)
===============================================================================/]

[section Number List - stuffing numbers into a std::vector]

This sample demonstrates a parser for a comma separated list of numbers and
using a semantic action to collect the numbers into a `std::vector`.

    template <typename Iterator>
    bool parse_numbers(Iterator first, Iterator last, std::vector<double>& v)
    {
        using x3::double_;
        using x3::phrase_parse;
        using x3::_attr;
        using ascii::space;

        auto push_back = [&](auto& ctx){ v.push_back(_attr(ctx)); };

        bool r = phrase_parse(first, last,

            //  Begin grammar
            (
                double_[push_back]
                    >> *(',' >> double_[push_back])
            )
            ,
            //  End grammar

            space);

        if (first != last) // fail if we did not get a full match
            return false;
        return r;
    }

The full cpp file for this example can be found here:
[@../../../example/x3/num_list/num_list2.cpp num_list2.cpp]

This, again, is the same parser as before. This time, instead of summing up the
numbers, we stuff them in a `std::vector`.

    [&](auto& ctx){ v.push_back(_attr(ctx)); }

[endsect]