63e88f80
 Hu Chunming
提交三方库
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/*=============================================================================
Copyright (c) 2015 Paul Fultz II
flip.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_FLIP_H
#define BOOST_HOF_GUARD_FLIP_H
/// flip
/// ====
///
/// Description
/// -----------
///
/// The `flip` function adaptor swaps the first two parameters.
///
/// Synopsis
/// --------
///
/// template<class F>
/// flip_adaptor<F> flip(F f);
///
/// Semantics
/// ---------
///
/// assert(flip(f)(x, y, xs...) == f(y, x, xs...));
///
/// Requirements
/// ------------
///
/// F must be at least:
///
/// * [BinaryInvocable](BinaryInvocable)
///
/// Or:
///
/// * [Invocable](Invocable) with more than two argurments
///
/// And:
///
/// * MoveConstructible
///
/// Example
/// -------
///
/// #include <boost/hof.hpp>
/// #include <cassert>
///
/// int main() {
/// int r = boost::hof::flip(boost::hof::_ - boost::hof::_)(2, 5);
/// assert(r == 3);
/// }
///
#include <boost/hof/detail/callable_base.hpp>
#include <boost/hof/reveal.hpp>
#include <boost/hof/detail/make.hpp>
#include <boost/hof/detail/static_const_var.hpp>
namespace boost { namespace hof {
template<class F>
struct flip_adaptor : detail::callable_base<F>
{
typedef flip_adaptor fit_rewritable1_tag;
BOOST_HOF_INHERIT_CONSTRUCTOR(flip_adaptor, detail::callable_base<F>);
template<class... Ts>
constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const
{
return boost::hof::always_ref(*this)(xs...);
}
struct flip_failure
{
template<class Failure>
struct apply
{
template<class T, class U, class... Ts>
struct of
: Failure::template of<U, T, Ts...>
{};
};
};
struct failure
: failure_map<flip_failure, detail::callable_base<F>>
{};
BOOST_HOF_RETURNS_CLASS(flip_adaptor);
template<class T, class U, class... Ts>
constexpr BOOST_HOF_SFINAE_RESULT(const detail::callable_base<F>&, id_<U>, id_<T>, id_<Ts>...)
operator()(T&& x, U&& y, Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
(
(BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(xs...)))
(BOOST_HOF_FORWARD(U)(y), BOOST_HOF_FORWARD(T)(x), BOOST_HOF_FORWARD(Ts)(xs)...)
);
};
BOOST_HOF_DECLARE_STATIC_VAR(flip, detail::make<flip_adaptor>);
}} // namespace boost::hof
#endif
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