ceph/src/boost/libs/fusion/include/boost/fusion/algorithm/transformation/detail/replace.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_REPLACE_08182005_0841)
   8 #define FUSION_REPLACE_08182005_0841
   9
  10 #include <boost/fusion/support/config.hpp>
  11 #include <boost/type_traits/is_convertible.hpp>
  12 #include <boost/mpl/if.hpp>
  13 #include <boost/type_traits/remove_reference.hpp>
  14
  15 namespace boost { namespace fusion { namespace detail
  16 {
  17     template <bool is_convertible>
  18     struct replacer_helper;
  19
  20     template <>
  21     struct replacer_helper<false>
  22     {
  23         template <typename U, typename T>
  24         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  25         static U&
  26         call(U& x, T const&, T const&)
  27         {
  28             return x;
  29         }
  30     };
  31
  32     template <>
  33     struct replacer_helper<true>
  34     {
  35         template <typename U, typename T>
  36         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  37         static U
  38         call(U& x, T const& old_value, T const& new_value)
  39         {
  40             return (x == old_value) ? new_value : x;
  41         }
  42     };
  43
  44     template <typename T>
  45     struct replacer
  46     {
  47         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  48         replacer(T const& in_old_value, T const& in_new_value)
  49             : old_value(in_old_value), new_value(in_new_value) {}
  50
  51         template<typename Sig>
  52         struct result;
  53
  54         template <typename U1, typename U2>
  55         struct result<replacer<U1>(U2)>
  56         {
  57             typedef typename remove_reference<U2>::type value;
  58             typedef typename
  59                 mpl::if_<is_convertible<T, value>, value, value const&>::type
  60             type;
  61         };
  62
  63         template <typename U>
  64         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  65         typename result<replacer(U)>::type
  66         operator()(U const& x) const
  67         {
  68             return replacer_helper<is_convertible<T, U>::value>::
  69                 call(x, old_value, new_value);
  70         }
  71
  72         T old_value;
  73         T new_value;
  74     };
  75 }}}
  76
  77 #endif
  78