1/*============================================================================= 2 Copyright (c) 2015 Paul Fultz II 3 decay.h 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 8#ifndef BOOST_HOF_GUARD_DECAY_H 9#define BOOST_HOF_GUARD_DECAY_H 10 11/// decay 12/// ===== 13/// 14/// Description 15/// ----------- 16/// 17/// The `decay` function is a unary function object that returns whats given to it after decaying its type. 18/// 19/// Synopsis 20/// -------- 21/// 22/// struct 23/// { 24/// template<class T> 25/// constexpr typename decay<T>::type operator()(T&& x) const 26/// { 27/// return boost::hof::forward<T>(x); 28/// } 29/// } decay; 30/// 31/// References 32/// ---------- 33/// 34/// * [n3255](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3255.html) - Proposal for `decay_copy` 35/// 36 37#include <boost/hof/detail/delegate.hpp> 38#include <boost/hof/detail/unwrap.hpp> 39#include <boost/hof/detail/static_const_var.hpp> 40#include <boost/hof/detail/forward.hpp> 41 42namespace boost { namespace hof { namespace detail { 43 44template<class T> 45struct decay_mf 46: unwrap_reference<typename std::decay<T>::type> 47{}; 48 49struct decay_f 50{ 51 template< 52 class T, 53 class Result=typename unwrap_reference<typename std::decay<T>::type>::type, 54 class=typename std::enable_if<(BOOST_HOF_IS_CONSTRUCTIBLE(Result, T))>::type 55 > 56 constexpr Result operator()(T&& x) const BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(Result, T&&) 57 { 58 return BOOST_HOF_FORWARD(T)(x); 59 } 60}; 61 62} 63 64BOOST_HOF_DECLARE_STATIC_VAR(decay, detail::decay_f); 65 66}} // namespace boost::hof 67 68#endif 69