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