135 lines
4.1 KiB
C++
135 lines
4.1 KiB
C++
/**
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This file is a part of rexy's general purpose library
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Copyright (C) 2022 rexy712
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef REXY_UTIL_DEFERRED_HPP
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#define REXY_UTIL_DEFERRED_HPP
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#include <tuple>
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#include <utility> //forward, index_sequence
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#include <cstddef> //size_t
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#include "compat/standard.hpp"
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namespace rexy{
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template<class T, class... Args>
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class deferred
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{
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public:
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using value_type = T;
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private:
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std::tuple<Args&&...> m_args;
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public:
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template<class... FArgs>
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constexpr deferred(FArgs&&... args);
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REXY_CPP20_CONSTEXPR deferred(const deferred&) = default;
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REXY_CPP20_CONSTEXPR deferred(deferred&&) = default;
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REXY_CPP20_CONSTEXPR ~deferred(void) = default;
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REXY_CPP20_CONSTEXPR deferred& operator=(const deferred&) = default;
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REXY_CPP20_CONSTEXPR deferred& operator=(deferred&&) = default;
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constexpr value_type value(void);
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constexpr operator value_type(void);
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private:
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template<std::size_t... Is>
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constexpr value_type get_value_(std::index_sequence<Is...>);
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};
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template<class Fn, class... Args>
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class deferred_function
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{
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public:
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using ret_t = decltype(std::declval<Fn>()(std::declval<Args>()...));
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private:
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Fn m_fn;
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std::tuple<Args&&...> m_args;
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public:
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template<class F, class... FArgs>
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constexpr deferred_function(F&& f, FArgs&&... args);
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constexpr decltype(auto) operator()(void);
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constexpr decltype(auto) value(void);
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constexpr operator ret_t(void);
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private:
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template<std::size_t... Is>
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constexpr decltype(auto) get_value_(std::index_sequence<Is...>);
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};
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template<class T, class... Args>
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template<class... FArgs>
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constexpr deferred<T,Args...>::deferred(FArgs&&... args):
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m_args{std::forward<FArgs>(args)...}{}
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template<class T, class... Args>
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constexpr auto deferred<T,Args...>::value(void) -> value_type{
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return get_value_(std::make_index_sequence<sizeof...(Args)>());
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}
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template<class T, class... Args>
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constexpr deferred<T,Args...>::operator value_type(void){
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return get_value_(std::make_index_sequence<sizeof...(Args)>());
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}
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template<class T, class... Args>
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template<std::size_t... Is>
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constexpr auto deferred<T,Args...>::get_value_(std::index_sequence<Is...>) -> value_type{
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return T{std::forward<std::tuple_element_t<Is,decltype(m_args)>>(std::get<Is>(m_args))...};
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}
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template<class Fn, class... Args>
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template<class F, class... FArgs>
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constexpr deferred_function<Fn,Args...>::deferred_function(F&& f, FArgs&&... args):
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m_fn(std::forward<F>(f)),
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m_args{std::forward<FArgs>(args)...}{}
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template<class Fn, class... Args>
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constexpr decltype(auto) deferred_function<Fn,Args...>::operator()(void){
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return get_value_(std::make_index_sequence<sizeof...(Args)>());
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}
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template<class Fn, class... Args>
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constexpr decltype(auto) deferred_function<Fn,Args...>::value(void){
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return get_value_(std::make_index_sequence<sizeof...(Args)>());
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}
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template<class Fn, class... Args>
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constexpr deferred_function<Fn,Args...>::operator ret_t(void){
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return get_value_(std::make_index_sequence<sizeof...(Args)>());
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}
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template<class Fn, class... Args>
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template<std::size_t... Is>
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constexpr decltype(auto) deferred_function<Fn,Args...>::get_value_(std::index_sequence<Is...>){
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return std::forward<Fn>(m_fn)(std::forward<std::tuple_element_t<Is,decltype(m_args)>>(std::get<Is>(m_args))...);
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}
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template<class Fn, class... Args>
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deferred_function(Fn&&, Args&&...) -> deferred_function<Fn&&, Args&&...>;
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template<class T, class... Args>
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deferred<T,Args...> make_deferred(Args&&... args){
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return deferred<T,Args...>(std::forward<Args>(args)...);
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}
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}
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#endif
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