| 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 | |
| 42 | namespace boost { namespace hof { namespace detail { |
| 43 | |
| 44 | template<class T> |
| 45 | struct decay_mf |
| 46 | : unwrap_reference<typename std::decay<T>::type> |
| 47 | {}; |
| 48 | |
| 49 | struct 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 | |
| 64 | BOOST_HOF_DECLARE_STATIC_VAR(decay, detail::decay_f); |
| 65 | |
| 66 | }} // namespace boost::hof |
| 67 | |
| 68 | #endif |
| 69 |