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 Hu Chunming
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/*=============================================================================
Copyright (c) 2015 Paul Fultz II
decay.h
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)
==============================================================================*/
#ifndef BOOST_HOF_GUARD_DECAY_H
#define BOOST_HOF_GUARD_DECAY_H
/// decay
/// =====
///
/// Description
/// -----------
///
/// The `decay` function is a unary function object that returns whats given to it after decaying its type.
///
/// Synopsis
/// --------
///
/// struct
/// {
/// template<class T>
/// constexpr typename decay<T>::type operator()(T&& x) const
/// {
/// return boost::hof::forward<T>(x);
/// }
/// } decay;
///
/// References
/// ----------
///
/// * [n3255](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3255.html) - Proposal for `decay_copy`
///
#include <boost/hof/detail/delegate.hpp>
#include <boost/hof/detail/unwrap.hpp>
#include <boost/hof/detail/static_const_var.hpp>
#include <boost/hof/detail/forward.hpp>
namespace boost { namespace hof { namespace detail {
template<class T>
struct decay_mf
: unwrap_reference<typename std::decay<T>::type>
{};
struct decay_f
{
template<
class T,
class Result=typename unwrap_reference<typename std::decay<T>::type>::type,
class=typename std::enable_if<(BOOST_HOF_IS_CONSTRUCTIBLE(Result, T))>::type
>
constexpr Result operator()(T&& x) const BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(Result, T&&)
{
return BOOST_HOF_FORWARD(T)(x);
}
};
}
BOOST_HOF_DECLARE_STATIC_VAR(decay, detail::decay_f);
}} // namespace boost::hof
#endif
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