ceph/src/boost/libs/spirit/doc/x3/tutorial/num_list2.qbk

   1 [/==============================================================================
   2     Copyright (C) 2001-2015 Joel de Guzman
   3     Copyright (C) 2001-2011 Hartmut Kaiser
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 ===============================================================================/]
   8
   9 [section Number List - stuffing numbers into a std::vector]
  10
  11 This sample demonstrates a parser for a comma separated list of numbers and
  12 using a semantic action to collect the numbers into a `std::vector`.
  13
  14     template <typename Iterator>
  15     bool parse_numbers(Iterator first, Iterator last, std::vector<double>& v)
  16     {
  17         using x3::double_;
  18         using x3::phrase_parse;
  19         using x3::_attr;
  20         using ascii::space;
  21
  22         auto push_back = [&](auto& ctx){ v.push_back(_attr(ctx)); };
  23
  24         bool r = phrase_parse(first, last,
  25
  26             //  Begin grammar
  27             (
  28                 double_[push_back]
  29                     >> *(',' >> double_[push_back])
  30             )
  31             ,
  32             //  End grammar
  33
  34             space);
  35
  36         if (first != last) // fail if we did not get a full match
  37             return false;
  38         return r;
  39     }
  40
  41 The full cpp file for this example can be found here: [@../../../example/x3/num_list/num_list2.cpp]
  42
  43 This, again, is the same parser as before. This time, instead of summing up the
  44 numbers, we stuff them in a `std::vector`.
  45
  46     [&](auto& ctx){ v.push_back(_attr(ctx)); }
  47
  48 [endsect]