86 lines
3.0 KiB
C++
86 lines
3.0 KiB
C++
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/*!
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@file
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Defines `boost::hana::apply`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_FUNCTIONAL_APPLY_HPP
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#define BOOST_HANA_FUNCTIONAL_APPLY_HPP
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#include <boost/hana/config.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @ingroup group-functional
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//! Invokes a Callable with the given arguments.
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//!
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//! This is equivalent to [std::invoke][1] that will be added in C++17.
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//! However, `apply` is a function object instead of a function, which
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//! makes it possible to pass it to higher-order algorithms.
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//!
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//!
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//! @param f
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//! A [Callable][2] to be invoked with the given arguments.
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//!
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//! @param x...
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//! The arguments to call `f` with. The number of `x...` must match the
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//! arity of `f`.
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//!
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//!
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//! Example
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//! -------
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//! @include example/functional/apply.cpp
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//!
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//! [1]: http://en.cppreference.com/w/cpp/utility/functional/invoke
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//! [2]: http://en.cppreference.com/w/cpp/concept/Callable
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto apply = [](auto&& f, auto&& ...x) -> decltype(auto) {
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return forwarded(f)(forwarded(x)...);
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};
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#else
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struct apply_t {
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template <typename F, typename... Args>
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constexpr auto operator()(F&& f, Args&&... args) const ->
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decltype(static_cast<F&&>(f)(static_cast<Args&&>(args)...))
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{
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return static_cast<F&&>(f)(static_cast<Args&&>(args)...);
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}
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template <typename Base, typename T, typename Derived>
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constexpr auto operator()(T Base::*pmd, Derived&& ref) const ->
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decltype(static_cast<Derived&&>(ref).*pmd)
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{
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return static_cast<Derived&&>(ref).*pmd;
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}
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template <typename PMD, typename Pointer>
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constexpr auto operator()(PMD pmd, Pointer&& ptr) const ->
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decltype((*static_cast<Pointer&&>(ptr)).*pmd)
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{
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return (*static_cast<Pointer&&>(ptr)).*pmd;
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}
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template <typename Base, typename T, typename Derived, typename... Args>
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constexpr auto operator()(T Base::*pmf, Derived&& ref, Args&&... args) const ->
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decltype((static_cast<Derived&&>(ref).*pmf)(static_cast<Args&&>(args)...))
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{
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return (static_cast<Derived&&>(ref).*pmf)(static_cast<Args&&>(args)...);
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}
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template <typename PMF, typename Pointer, typename... Args>
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constexpr auto operator()(PMF pmf, Pointer&& ptr, Args&& ...args) const ->
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decltype(((*static_cast<Pointer&&>(ptr)).*pmf)(static_cast<Args&&>(args)...))
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{
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return ((*static_cast<Pointer&&>(ptr)).*pmf)(static_cast<Args&&>(args)...);
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}
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};
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constexpr apply_t apply{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FUNCTIONAL_APPLY_HPP
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