| /*============================================================================= | |
| 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 in_f, T const& in_new_value) | |
| : f(in_f), new_value(in_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 | |