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157 lines
4.6 KiB
C++
157 lines
4.6 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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reverse_compress.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 FIT_GUARD_REVERSE_COMPRESS_H
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#define FIT_GUARD_REVERSE_COMPRESS_H
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/// reverse_compress
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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 `reverse_compress` function adaptor uses a binary function to apply a
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/// reverse fold(ie right fold in functional programming terms) operation to
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/// the arguments passed to the function. Additionally, an optional initial
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/// state can be provided, otherwise the first argument is used as the initial
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/// state.
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///
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/// The arguments to the binary function, take first the state and then the
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/// argument.
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///
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/// Synopsis
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/// --------
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///
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/// template<class F, class State>
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/// constexpr reverse_compress_adaptor<F, State> reverse_compress(F f, State s);
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///
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/// template<class F>
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/// constexpr reverse_compress_adaptor<F> reverse_compress(F f);
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///
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/// Semantics
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/// ---------
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///
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/// assert(reverse_compress(f, z)() == z);
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/// assert(reverse_compress(f, z)(x, xs...) == f(reverse_compress(f, z)(xs...), x));
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/// assert(reverse_compress(f)(x) == x);
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/// assert(reverse_compress(f)(x, xs...) == f(reverse_compress(f)(xs...), x));
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///
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/// Requirements
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/// ------------
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///
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/// State must be:
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///
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/// * CopyConstructible
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///
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/// F must be:
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///
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/// * [BinaryCallable](concepts.md#binarycallable)
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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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/// struct max_f
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/// {
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/// template<class T, class U>
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/// constexpr T operator()(T x, U y) const
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/// {
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/// return x > y ? x : y;
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/// }
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/// };
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/// assert(fit::reverse_compress(max_f())(2, 3, 4, 5) == 5);
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///
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#include <fit/detail/callable_base.hpp>
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#include <fit/detail/delegate.hpp>
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#include <fit/detail/compressed_pair.hpp>
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#include <fit/detail/move.hpp>
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#include <fit/detail/make.hpp>
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#include <fit/detail/static_const_var.hpp>
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namespace fit { namespace detail {
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struct v_reverse_fold
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{
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FIT_RETURNS_CLASS(v_reverse_fold);
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template<class F, class State, class T, class... Ts>
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constexpr FIT_SFINAE_MANUAL_RESULT(const F&, result_of<const v_reverse_fold&, id_<const F&>, id_<State>, id_<Ts>...>, id_<T>)
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operator()(const F& f, State&& state, T&& x, Ts&&... xs) const FIT_SFINAE_MANUAL_RETURNS
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(
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f((*FIT_CONST_THIS)(f, FIT_FORWARD(State)(state), FIT_FORWARD(Ts)(xs)...), FIT_FORWARD(T)(x))
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);
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template<class F, class State>
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constexpr State operator()(const F&, State&& state) const
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{
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return FIT_FORWARD(State)(state);
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}
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};
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}
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template<class F, class State=void>
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struct reverse_compress_adaptor
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: detail::compressed_pair<detail::callable_base<F>, State>
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{
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typedef detail::compressed_pair<detail::callable_base<F>, State> base_type;
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FIT_INHERIT_CONSTRUCTOR(reverse_compress_adaptor, base_type)
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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 this->first(xs...);
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}
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template<class... Ts>
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constexpr State get_state(Ts&&... xs) const
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{
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return this->second(xs...);
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}
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template<class... Ts>
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constexpr FIT_SFINAE_RESULT(detail::v_reverse_fold, id_<const detail::callable_base<F>&>, id_<State>, id_<Ts>...)
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operator()(Ts&&... xs) const FIT_SFINAE_RETURNS
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(
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detail::v_reverse_fold()(
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FIT_MANGLE_CAST(const detail::callable_base<F>&)(this->base_function(xs...)),
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FIT_MANGLE_CAST(State)(this->get_state(xs...)),
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FIT_FORWARD(Ts)(xs)...
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)
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)
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};
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template<class F>
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struct reverse_compress_adaptor<F, void>
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: detail::callable_base<F>
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{
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FIT_INHERIT_CONSTRUCTOR(reverse_compress_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 always_ref(*this)(xs...);
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}
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template<class... Ts>
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constexpr FIT_SFINAE_RESULT(detail::v_reverse_fold, id_<const detail::callable_base<F>&>, id_<Ts>...)
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operator()(Ts&&... xs) const FIT_SFINAE_RETURNS
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(
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detail::v_reverse_fold()(
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FIT_MANGLE_CAST(const detail::callable_base<F>&)(this->base_function(xs...)),
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FIT_FORWARD(Ts)(xs)...
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)
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)
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};
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FIT_DECLARE_STATIC_VAR(reverse_compress, detail::make<reverse_compress_adaptor>);
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} // namespace fit
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#endif
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