bump version to 12.2.2-pve1

[ceph.git] / ceph / src / boost / libs / spirit / doc / x3 / tutorial / num_list3.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 Redux - list syntax]


So far, we've been using the syntax:

    double_ >> *(',' >> double_)

to parse a comma-delimited list of numbers. Such lists are common in parsing and
Spirit provides a simpler shortcut for them. The expression above can be
simplified to:

    double_ % ','

read as: a list of doubles separated by `','`.

This sample, again a variation of our previous example, demonstrates just that:

    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] % ','
            )
            ,
            //  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_list3.cpp]

[endsect]