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authorDongHun Kwak <dh0128.kwak@samsung.com>2019-12-05 15:12:59 +0900
committerDongHun Kwak <dh0128.kwak@samsung.com>2019-12-05 15:12:59 +0900
commitb8cf34c691623e4ec329053cbbf68522a855882d (patch)
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parent3fdc3e5ee96dca5b11d1694975a65200787eab86 (diff)
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Imported Upstream version 1.67.0upstream/1.67.0
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+/*=============================================================================
+ Copyright (c) 2015 Paul Fultz II
+ capture.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_CAPTURE_H
+#define BOOST_HOF_GUARD_CAPTURE_H
+
+#include <boost/hof/detail/callable_base.hpp>
+#include <boost/hof/detail/compressed_pair.hpp>
+#include <boost/hof/reveal.hpp>
+#include <boost/hof/pack.hpp>
+#include <boost/hof/always.hpp>
+#include <boost/hof/detail/move.hpp>
+#include <boost/hof/detail/result_type.hpp>
+
+/// capture
+/// =======
+///
+/// Description
+/// -----------
+///
+/// The `capture` function decorator is used to capture values in a function.
+/// It provides more flexibility in capturing than the lambda capture list in
+/// C++. It provides a way to do move and perfect capturing. The values
+/// captured are prepended to the argument list of the function that will be
+/// called.
+///
+/// Synopsis
+/// --------
+///
+/// // Capture by decaying each value
+/// template<class... Ts>
+/// constexpr auto capture(Ts&&... xs);
+///
+/// // Capture lvalues by reference and rvalue reference by reference
+/// template<class... Ts>
+/// constexpr auto capture_forward(Ts&&... xs);
+///
+/// // Capture lvalues by reference and rvalues by value.
+/// template<class... Ts>
+/// constexpr auto capture_basic(Ts&&... xs);
+///
+/// Semantics
+/// ---------
+///
+/// assert(capture(xs...)(f)(ys...) == f(xs..., ys...));
+///
+///
+/// Example
+/// -------
+///
+/// #include <boost/hof.hpp>
+/// #include <cassert>
+///
+/// struct sum_f
+/// {
+/// template<class T, class U>
+/// T operator()(T x, U y) const
+/// {
+/// return x+y;
+/// }
+/// };
+///
+/// int main() {
+/// auto add_one = boost::hof::capture(1)(sum_f());
+/// assert(add_one(2) == 3);
+/// }
+///
+
+namespace boost { namespace hof {
+
+namespace detail {
+
+template<class F, class Pack>
+struct capture_invoke : detail::compressed_pair<detail::callable_base<F>, Pack>, detail::function_result_type<F>
+{
+ typedef capture_invoke fit_rewritable1_tag;
+ typedef detail::compressed_pair<detail::callable_base<F>, Pack> base;
+ BOOST_HOF_INHERIT_CONSTRUCTOR(capture_invoke, base)
+ template<class... Ts>
+ constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const noexcept
+ {
+ return this->first(xs...);
+ }
+
+ template<class... Ts>
+ constexpr const Pack& get_pack(Ts&&...xs) const noexcept
+ {
+ return this->second(xs...);
+ }
+
+ template<class Failure, class... Ts>
+ struct unpack_capture_failure
+ {
+ template<class... Us>
+ struct apply
+ {
+ typedef typename Failure::template of<Us..., Ts...> type;
+ };
+ };
+
+ struct capture_failure
+ {
+ template<class Failure>
+ struct apply
+ {
+ template<class... Ts>
+ struct of
+ : Pack::template apply<unpack_capture_failure<Failure, Ts...>>::type
+ {};
+ };
+ };
+
+ struct failure
+ : failure_map<capture_failure, detail::callable_base<F>>
+ {};
+
+ BOOST_HOF_RETURNS_CLASS(capture_invoke);
+
+ template<class... Ts>
+ constexpr BOOST_HOF_SFINAE_RESULT
+ (
+ typename result_of<decltype(boost::hof::pack_join),
+ id_<const Pack&>,
+ result_of<decltype(boost::hof::pack_forward), id_<Ts>...>
+ >::type,
+ id_<detail::callable_base<F>&&>
+ )
+ operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
+ (
+ boost::hof::pack_join
+ (
+ BOOST_HOF_MANGLE_CAST(const Pack&)(BOOST_HOF_CONST_THIS->get_pack(xs...)),
+ boost::hof::pack_forward(BOOST_HOF_FORWARD(Ts)(xs)...)
+ )
+ (BOOST_HOF_RETURNS_C_CAST(detail::callable_base<F>&&)(BOOST_HOF_CONST_THIS->base_function(xs...)))
+ );
+};
+
+template<class Pack>
+struct capture_pack : Pack
+{
+ BOOST_HOF_INHERIT_CONSTRUCTOR(capture_pack, Pack);
+
+ BOOST_HOF_RETURNS_CLASS(capture_pack);
+
+ // TODO: Should use rvalue ref qualifier
+ template<class F>
+ constexpr auto operator()(F f) const BOOST_HOF_SFINAE_RETURNS
+ (
+ capture_invoke<F, Pack>(BOOST_HOF_RETURNS_STATIC_CAST(F&&)(f),
+ BOOST_HOF_RETURNS_C_CAST(Pack&&)(
+ BOOST_HOF_RETURNS_STATIC_CAST(const Pack&)(*boost::hof::always(BOOST_HOF_CONST_THIS)(f))
+ )
+ )
+ );
+};
+
+struct make_capture_pack_f
+{
+ template<class Pack>
+ constexpr capture_pack<Pack> operator()(Pack p) const
+ BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(capture_pack<Pack>, Pack&&)
+ {
+ return capture_pack<Pack>(static_cast<Pack&&>(p));
+ }
+};
+
+template<class F>
+struct capture_f
+{
+ template<class... Ts>
+ constexpr auto operator()(Ts&&... xs) const BOOST_HOF_RETURNS
+ (
+ BOOST_HOF_RETURNS_CONSTRUCT(make_capture_pack_f)()(BOOST_HOF_RETURNS_CONSTRUCT(F)()(BOOST_HOF_FORWARD(Ts)(xs)...))
+ );
+};
+}
+
+BOOST_HOF_DECLARE_STATIC_VAR(capture_basic, detail::capture_f<detail::pack_basic_f>);
+BOOST_HOF_DECLARE_STATIC_VAR(capture_forward, detail::capture_f<detail::pack_forward_f>);
+BOOST_HOF_DECLARE_STATIC_VAR(capture, detail::capture_f<detail::pack_f>);
+
+}} // namespace boost::hof
+
+#endif