| /*============================================================================= |
| 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_IF_08182005_0946) |
| #define FUSION_REPLACE_IF_08182005_0946 |
| |
| #include <boost/utility/enable_if.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_if_helper; |
| |
| template <> |
| struct replacer_if_helper<false> |
| { |
| template <typename U, typename F, typename T> |
| static U& |
| call(U& x, F&, T const&) |
| { |
| return x; |
| } |
| }; |
| |
| template <> |
| struct replacer_if_helper<true> |
| { |
| template <typename U, typename F, typename T> |
| static U |
| call(U& x, F& f, T const& new_value) |
| { |
| return f(x) ? new_value : x; |
| } |
| }; |
| |
| template <typename F, typename T> |
| struct replacer_if |
| { |
| replacer_if(F f, T const& new_value) |
| : f(f), new_value(new_value) {} |
| |
| template<typename Params> |
| struct result; |
| |
| template <typename F1, typename T1, typename U> |
| struct result<replacer_if<F1, T1>(U)> |
| { |
| typedef typename remove_reference<U>::type value; |
| typedef typename |
| mpl::if_<is_convertible<T, value>, value, value const&>::type |
| type; |
| }; |
| |
| template <typename U> |
| typename result<replacer_if(U)>::type |
| operator()(U const& x) const |
| { |
| return replacer_if_helper<is_convertible<T, U>::value>:: |
| call(x, f, new_value); |
| } |
| |
| F f; |
| T new_value; |
| }; |
| }}} |
| |
| #endif |
| |