| /*============================================================================= |
| Copyright (c) 2001-2006 Joel de Guzman |
| |
| 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) |
| ==============================================================================*/ |
| #if !defined(FUSION_REPLACE_08182005_0841) |
| #define FUSION_REPLACE_08182005_0841 |
| |
| #include <boost/type_traits/is_convertible.hpp> |
| #include <boost/mpl/if.hpp> |
| #include <boost/type_traits/remove_reference.hpp> |
| |
| namespace boost { namespace fusion { namespace detail |
| { |
| template <bool is_convertible> |
| struct replacer_helper; |
| |
| template <> |
| struct replacer_helper<false> |
| { |
| template <typename U, typename T> |
| static U& |
| call(U& x, T const&, T const&) |
| { |
| return x; |
| } |
| }; |
| |
| template <> |
| struct replacer_helper<true> |
| { |
| template <typename U, typename T> |
| static U |
| call(U& x, T const& old_value, T const& new_value) |
| { |
| return (x == old_value) ? new_value : x; |
| } |
| }; |
| |
| template <typename T> |
| struct replacer |
| { |
| replacer(T const& in_old_value, T const& in_new_value) |
| : old_value(in_old_value), new_value(in_new_value) {} |
| |
| template<typename Sig> |
| struct result; |
| |
| template <typename U1, typename U2> |
| struct result<replacer<U1>(U2)> |
| { |
| typedef typename remove_reference<U2>::type value; |
| typedef typename |
| mpl::if_<is_convertible<T, value>, value, value const&>::type |
| type; |
| }; |
| |
| template <typename U> |
| typename result<replacer(U)>::type |
| operator()(U const& x) const |
| { |
| return replacer_helper<is_convertible<T, U>::value>:: |
| call(x, old_value, new_value); |
| } |
| |
| T old_value; |
| T new_value; |
| }; |
| }}} |
| |
| #endif |
| |