464 lines
14 KiB
C++
464 lines
14 KiB
C++
#pragma once
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/*
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* Copyright (C) 2024 Brett Terpstra
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*
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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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*
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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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*
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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 <https://www.gnu.org/licenses/>.
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*/
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#ifndef BLT_STD_VARIANT_H
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#define BLT_STD_VARIANT_H
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#include <functional>
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#include <optional>
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#include <tuple>
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#include <type_traits>
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#include <variant>
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#include <blt/logging/logging.h>
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#include <blt/meta/function.h>
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#include <blt/meta/passthrough.h>
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#include <blt/meta/tuple_filters.h>
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#include <blt/std/types.h>
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namespace blt
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{
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template <typename... Types>
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class variant_t;
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namespace detail
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{
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template <typename Type, typename Func, typename... Args>
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struct member_func_meta
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{
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using can_invoke = std::is_invocable<Func, Type, Args...>;
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using return_type = typename std::conditional_t<can_invoke::value, std::invoke_result<Func, Type, Args...>, meta::passthrough<void>>::type
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;
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};
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template <typename Func, typename ArgsTuple, typename... Types>
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struct member_call_return_type;
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template <typename Func, typename... Args, typename... Types>
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struct member_call_return_type<Func, std::tuple<Args...>, Types...>
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{
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using result_types = std::tuple<member_func_meta<Types, Func, Args...>...>;
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using non_void_result_types = meta::filter_void_t<typename member_func_meta<Types, Func, Args...>::return_type...>;
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static constexpr bool all_void = std::tuple_size_v<non_void_result_types> == 0;
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static constexpr bool some_void = std::tuple_size_v<non_void_result_types> != sizeof...(Types);
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using first_return = std::conditional_t<all_void, void, std::tuple_element_t<0, non_void_result_types>>;
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using return_type = std::conditional_t<all_void, void, std::conditional_t<some_void, std::optional<first_return>, first_return>>;
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};
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template <typename Func, typename... Types>
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struct visit_func_meta
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{
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using result_tuple = std::tuple<typename std::conditional_t<
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std::is_invocable_v<Func, Types>, std::invoke_result<Func, Types>, meta::passthrough<void>>::type...>;
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using non_void_results = meta::filter_void_t<result_tuple>;
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using return_type = std::tuple_element_t<
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0, std::conditional_t<std::tuple_size_v<non_void_results> == 0, std::tuple<void>, non_void_results>>;
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};
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template <typename FuncTuple, typename TypesTuple>
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struct visit_return_type;
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template <typename... Funcs, typename... Types>
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struct visit_return_type<std::tuple<Funcs...>, std::tuple<Types...>>
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{
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using return_tuple = std::tuple<typename visit_func_meta<Funcs, Types...>::return_type...>;
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using non_void_returns = meta::unique_tuple_t<meta::filter_void_t<return_tuple>>;
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using first_return = std::tuple_element_t<
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0, std::conditional_t<std::tuple_size_v<non_void_returns> == 0, std::tuple<void>, non_void_returns>>;
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static constexpr bool all_void = std::tuple_size_v<non_void_returns> == 0;
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static constexpr bool some_void = std::tuple_size_v<non_void_returns> != std::tuple_size_v<return_tuple>;
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using same_type = meta::filter_func_t<std::is_same, std::tuple<first_return>, non_void_returns>;
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static constexpr bool all_same = std::tuple_size_v<same_type> == std::tuple_size_v<non_void_returns>;
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using variant_type = typename meta::apply_tuple<variant_t, non_void_returns>::type;
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using base_type = std::conditional_t<all_same, first_return, variant_type>;
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using return_type = std::conditional_t<all_void, void, std::conditional_t<some_void, std::optional<base_type>, base_type>>;
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};
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}
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/*
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* std::visit(blt::lambda_visitor{
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* lambdas...
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* }, data_variant);
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*/
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template <typename... TLambdas>
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struct lambda_visitor : TLambdas...
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{
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using TLambdas::operator()...;
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};
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#if __cplusplus < 202002L
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// explicit deduction guide (not needed as of C++20)
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template <typename... TLambdas>
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lambda_visitor(TLambdas...) -> lambda_visitor<TLambdas...>;
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#endif
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template <typename... Types>
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class variant_t
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{
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public:
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using value_type = std::variant<Types...>;
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size_t variant_size = sizeof...(Types);
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constexpr variant_t(): m_variant()
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{}
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constexpr variant_t(const variant_t& variant) noexcept(std::is_nothrow_copy_constructible_v<value_type>): m_variant(variant.m_variant)
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{}
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constexpr variant_t(variant_t&& variant) noexcept(std::is_nothrow_move_constructible_v<value_type>): m_variant(std::move(variant.m_variant))
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{}
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explicit constexpr variant_t(const value_type& variant) noexcept(std::is_nothrow_copy_constructible_v<value_type>): m_variant(variant)
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{}
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explicit constexpr variant_t(value_type&& variant) noexcept(std::is_nothrow_move_constructible_v<value_type>): m_variant(std::move(variant))
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{}
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explicit constexpr variant_t(Types&&... args) noexcept(std::is_nothrow_constructible_v<value_type, Types...>): m_variant(
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std::forward<Types>(args)...)
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{}
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// template <typename T, std::enable_if_t<!std::is_same_v<std::decay_t<T>, variant_t>, bool> = true>
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// explicit constexpr variant_t(T&& t): m_variant(std::forward<T>(t))
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// {}
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// template<typename T>
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// constexpr variant_t(std::initializer_list<T> il): m_variant(*il.begin())
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// {
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// }
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template <typename T, typename... C_Args>
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explicit constexpr variant_t(std::in_place_type_t<T>, C_Args&&... args): m_variant(std::in_place_type<T>, std::forward<C_Args>(args)...)
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{}
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template <typename T, typename U, typename... C_Args>
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constexpr explicit variant_t(std::in_place_type_t<T>, std::initializer_list<U> il, C_Args&&... args): m_variant(
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std::in_place_type<T>, il, std::forward<C_Args>(args)...)
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{}
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template <size_t I, typename... C_Args>
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explicit constexpr variant_t(std::in_place_index_t<I>, C_Args&&... args): m_variant(std::in_place_index<I>, std::forward<C_Args>(args)...)
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{}
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template <std::size_t I, typename U, typename... C_Args>
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constexpr explicit variant_t(std::in_place_index_t<I>, std::initializer_list<U> il, C_Args&&... args): m_variant(
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std::in_place_index<I>, il, std::forward<C_Args>(args)...)
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{}
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template <typename T, typename... Args>
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T& emplace(Args&&... args)
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{
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return m_variant.template emplace<T>(std::forward<Args>(args)...);
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}
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template <typename T, typename U, typename... Args>
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T& emplace(std::initializer_list<U> il, Args&&... args)
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{
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return m_variant.template emplace<T>(il, std::forward<Args>(args)...);
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}
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template <std::size_t I, typename... Args>
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std::variant_alternative_t<I, value_type>& emplace(Args&&... args)
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{
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return m_variant.template emplace<I>(std::forward<Args>(args)...);
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}
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template <std::size_t I, typename U, typename... Args>
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std::variant_alternative_t<I, value_type>& emplace(std::initializer_list<U> il, Args&&... args)
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{
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return m_variant.template emplace<I>(il, std::forward<Args>(args)...);
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}
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[[nodiscard]] constexpr std::size_t index() const noexcept
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{
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return m_variant.index();
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}
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[[nodiscard]] constexpr bool valueless_by_exception() const noexcept
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{
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return m_variant.valueless_by_exception();
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}
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template <typename T>
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constexpr auto visit(T&& visitor) -> decltype(auto)
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{
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return std::visit(std::forward<T>(visitor), m_variant);
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}
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/**
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* Automatic visitor generation
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* @param visitees user lambdas
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*/
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template <typename... Visitee>
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constexpr auto visit(Visitee&&... visitees) -> decltype(auto)
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{
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using meta_t = detail::visit_return_type<std::tuple<Visitee...>, std::tuple<Types...>>;
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// BLT_TRACE(blt::type_string<typename meta_t::return_tuple>());
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BLT_TRACE(blt::type_string<typename meta_t::non_void_returns>());
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BLT_TRACE(blt::type_string<typename meta_t::same_type>());
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if constexpr (meta_t::all_same)
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{
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if constexpr (meta_t::some_void)
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{
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return std::visit(lambda_visitor{
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[&](std::tuple_element_t<0, typename meta::function_like<Visitee>::args_tuple> value) {
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if constexpr (std::is_void_v<typename meta::function_like<decltype(visitees)>::return_type>)
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{
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std::forward<Visitee>(visitees)(std::forward<decltype(value)>(value));
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return typename meta_t::return_type{};
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} else
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{
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return typename meta_t::return_type(
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std::forward<Visitee>(visitees)(std::forward<decltype(value)>(value))
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);
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}
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}...
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}, m_variant);
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} else
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{
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return std::visit(lambda_visitor{std::forward<Visitee>(visitees)...}, m_variant);
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}
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} else
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{
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if constexpr (meta_t::some_void)
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{
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return std::visit(lambda_visitor{
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[&](std::tuple_element_t<0, typename meta::function_like<Visitee>::args_tuple> value) {
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if constexpr (std::is_void_v<typename meta::function_like<decltype(visitees)>::return_type>)
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{
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std::forward<Visitee>(visitees)(std::forward<decltype(value)>(value));
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return typename meta_t::return_type{};
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} else
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{
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return typename meta_t::return_type(
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typename meta_t::base_type(std::forward<Visitee>(visitees)(std::forward<decltype(value)>(value)))
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);
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}
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}...
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}, m_variant);
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} else
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{
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return std::visit(lambda_visitor{
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[&](std::tuple_element_t<0, typename meta::function_like<Visitee>::args_tuple> value) {
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return typename meta_t::return_type{
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std::forward<Visitee>(visitees)(std::forward<decltype(value)>(value))
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};
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}...
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}, m_variant);
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}
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}
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}
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template <typename Default, typename... Visitee>
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constexpr auto visit_value(Default&& default_value, Visitee&&... visitees) -> decltype(auto)
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{
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return visit(std::forward<Visitee>(visitees)..., [default_value=std::forward<Default>(default_value)](auto&&) {
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return std::forward<Default>(default_value);
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});
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}
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template <typename MemberFunc, typename... Args>
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constexpr auto call_member(const MemberFunc func, Args&&... args) -> decltype(auto)
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{
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using meta = detail::member_call_return_type<MemberFunc, std::tuple<Args...>, Types...>;
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return visit([&](auto&& value) -> typename meta::return_type {
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if constexpr (std::is_invocable_v<MemberFunc, decltype(value), Args...>)
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return ((value).*(func))(std::forward<Args>(args)...);
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else
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return {};
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});
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}
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template <size_t I>
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[[nodiscard]] constexpr bool has_index() const noexcept
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{
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return m_variant.index() == I;
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}
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template <typename T>
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[[nodiscard]] constexpr bool has_type() const noexcept
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{
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return std::holds_alternative<T>(m_variant);
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}
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template <typename T>
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[[nodiscard]] constexpr auto get() -> decltype(auto)
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{
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return std::get<T>(m_variant);
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}
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template <typename T>
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[[nodiscard]] constexpr auto get() const -> decltype(auto)
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{
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return std::get<T>(m_variant);
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}
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template <size_t I>
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[[nodiscard]] constexpr auto get() -> decltype(auto)
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{
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return std::get<I>(m_variant);
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}
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template <size_t I>
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[[nodiscard]] constexpr auto get() const -> decltype(auto)
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{
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return std::get<I>(m_variant);
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}
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template <size_t I>
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constexpr std::add_pointer_t<std::variant_alternative_t<I, value_type>> get_if() noexcept
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{
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return std::get_if<I>(m_variant);
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}
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template <size_t I>
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constexpr std::add_pointer_t<const std::variant_alternative_t<I, value_type>> get_if() noexcept
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{
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return std::get_if<I>(m_variant);
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}
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template <typename T>
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constexpr std::add_pointer_t<T> get_if() noexcept
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{
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return std::get_if<T>(m_variant);
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}
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template <typename T>
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constexpr std::add_pointer_t<const T> get_if() noexcept
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{
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return std::get_if<T>(m_variant);
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}
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template <typename T>
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constexpr T value_or(T&& t) const
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{
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if (has_type<T>())
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return get<T>();
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return std::forward<T>(t);
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}
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template <size_t I>
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constexpr std::variant_alternative_t<I, value_type> value_or(const std::variant_alternative_t<I, value_type>& t) const
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{
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if (has_type<std::variant_alternative_t<I, value_type>>())
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return get<I>();
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return t;
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}
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template <size_t I>
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constexpr std::variant_alternative_t<I, value_type> value_or(std::variant_alternative_t<I, value_type>&& t) const
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{
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if (has_type<std::variant_alternative_t<I, value_type>>())
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return get<I>();
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return t;
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}
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template <size_t>
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constexpr const value_type& variant() const
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{
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return m_variant;
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}
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constexpr value_type& variant()
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{
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return m_variant;
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}
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[[nodiscard]] constexpr size_t size() const
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{
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return variant_size;
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}
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friend bool operator==(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant == rhs.m_variant;
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}
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friend bool operator!=(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant != rhs.m_variant;
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}
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friend bool operator<(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant < rhs.m_variant;
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}
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friend bool operator>(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant > rhs.m_variant;
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}
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friend bool operator<=(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant <= rhs.m_variant;
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}
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friend bool operator>=(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant >= rhs.m_variant;
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}
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private:
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value_type m_variant;
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};
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namespace detail
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{
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template <typename>
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class variant_is_base_of
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{};
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template <typename... Types>
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class variant_is_base_of<variant_t<Types...>>
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{
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public:
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using value_type = bool;
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template <typename T>
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static constexpr bool value = std::conjunction_v<std::is_base_of<T, Types>...>;
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};
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template <typename... Types>
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class variant_is_base_of<std::variant<Types...>>
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{
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public:
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using value_type = bool;
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template <typename T>
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static constexpr bool value = std::conjunction_v<std::is_base_of<T, Types>...>;
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};
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template <typename T>
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static constexpr bool variant_is_base_of_v = variant_is_base_of<T>::value;
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}
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}
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#endif //BLT_STD_VARIANT_H
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