/*============================================================================= | |
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 | |