boost/fusion/view/joint_view/detail/next_impl.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 Joel de Guzman
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7 #if !defined(FUSION_NEXT_IMPL_07162005_0136)
   8 #define FUSION_NEXT_IMPL_07162005_0136
   9
  10 #include <boost/fusion/iterator/next.hpp>
  11 #include <boost/fusion/iterator/equal_to.hpp>
  12 #include <boost/mpl/if.hpp>
  13
  14 namespace boost { namespace fusion
  15 {
  16     struct joint_view_iterator_tag;
  17
  18     template <typename Category, typename First, typename Last, typename Concat>
  19     struct joint_view_iterator;
  20
  21     namespace extension
  22     {
  23         template <typename Tag>
  24         struct next_impl;
  25
  26         template <>
  27         struct next_impl<joint_view_iterator_tag>
  28         {
  29             template <typename Iterator>
  30             struct apply
  31             {
  32                 typedef typename Iterator::first_type first_type;
  33                 typedef typename Iterator::last_type last_type;
  34                 typedef typename Iterator::concat_type concat_type;
  35                 typedef typename Iterator::category category;
  36                 typedef typename result_of::next<first_type>::type next_type;
  37                 typedef result_of::equal_to<next_type, last_type> equal_to;
  38
  39                 typedef typename
  40                     mpl::if_<
  41                         equal_to
  42                       , concat_type
  43                       , joint_view_iterator<category, next_type, last_type, concat_type>
  44                     >::type
  45                 type;
  46
  47                 static type
  48                 call(Iterator const& i, mpl::true_)
  49                 {
  50                     return i.concat;
  51                 }
  52
  53                 static type
  54                 call(Iterator const& i, mpl::false_)
  55                 {
  56                     return type(fusion::next(i.first), i.concat);
  57                 }
  58
  59                 static type
  60                 call(Iterator const& i)
  61                 {
  62                     return call(i, equal_to());
  63                 }
  64             };
  65         };
  66     }
  67 }}
  68
  69 #endif
  70
  71