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69 lines
1.7 KiB
C++
69 lines
1.7 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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decay.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef BOOST_HOF_GUARD_DECAY_H
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#define BOOST_HOF_GUARD_DECAY_H
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/// decay
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/// =====
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///
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/// Description
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/// -----------
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///
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/// The `decay` function is a unary function object that returns whats given to it after decaying its type.
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///
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/// Synopsis
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/// --------
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///
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/// struct
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/// {
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/// template<class T>
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/// constexpr typename decay<T>::type operator()(T&& x) const
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/// {
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/// return boost::hof::forward<T>(x);
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/// }
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/// } decay;
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///
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/// References
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/// ----------
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///
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/// * [n3255](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3255.html) - Proposal for `decay_copy`
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///
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#include <boost/hof/detail/delegate.hpp>
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#include <boost/hof/detail/unwrap.hpp>
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#include <boost/hof/detail/static_const_var.hpp>
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#include <boost/hof/detail/forward.hpp>
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namespace boost { namespace hof { namespace detail {
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template<class T>
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struct decay_mf
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: unwrap_reference<typename std::decay<T>::type>
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{};
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struct decay_f
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{
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template<
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class T,
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class Result=typename unwrap_reference<typename std::decay<T>::type>::type,
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class=typename std::enable_if<(BOOST_HOF_IS_CONSTRUCTIBLE(Result, T))>::type
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>
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constexpr Result operator()(T&& x) const BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(Result, T&&)
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{
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return BOOST_HOF_FORWARD(T)(x);
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}
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};
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}
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BOOST_HOF_DECLARE_STATIC_VAR(decay, detail::decay_f);
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}} // namespace boost::hof
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#endif
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