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243 lines
7.2 KiB
243 lines
7.2 KiB
#pragma once
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#include "gp_config.hpp"
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#include <gp/algorithms/move.hpp>
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#include <gp/algorithms/tmp_manip.hpp>
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#include "gp/utils/allocators/dummy.hpp"
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#include "gp/exception.hpp"
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#include "gp/functional/function.hpp"
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#include <type_traits>
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#include <new>
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// TODO: Implement the allocating flavour of variant
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namespace gp{
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/**
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* @brief A form of variant that expect only classes whose size is strictly defined at compile time
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*
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* @tparam T The list of types accepted by the variant
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*/
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template<typename ...T>
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class fixed_variant final {
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std::size_t index = std::numeric_limits<std::size_t>::max();
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alignas(gp::max(alignof(T)...)) char data[max_size<T...>()];
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gp::function<void(void*, void*)> cpytor = {[](void*, void*){}, nullopt};
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gp::function<void(void*, void*)> mvtor = {[](void*, void*){}, nullopt};
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gp::function<void(void*)> dtor = {[](void*){}, nullopt};
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static_assert(all_of_fixed_size<T...>::value, "not fixed");
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public:
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fixed_variant()
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: fixed_variant(typename first_of<T...>::type{})
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{}
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/**
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* @brief Construct a new fixed variant from an object that is legal in it
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*
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* @tparam U A type that belongs in the list of types the variant supports
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* @param value The copied value
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*/
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template<typename U, std::enable_if_t<list_contains_class<gp::remove_cvref_t<U>,T...>::value,int> = 0>
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fixed_variant(U& value)
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: index{r_index_of<gp::remove_cvref_t<U>, T...>::value}
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{
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using actual = gp::remove_cvref_t<U>;
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dtor = gp::function<void(void*)>([](void* thing){
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((actual*)thing)->~actual();
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}, nullopt);
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cpytor = gp::function<void(void*, void*)>([](void* src, void* dest){
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new(dest) actual(*(actual*)src);
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}, nullopt);
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mvtor = gp::function<void(void*, void*)>([](void* src, void* dest){
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new(dest) actual(gp::move(*(actual*)src));
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}, nullopt);
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cpytor((char*)&value, data);
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}
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static_assert(list_contains_class<int, int>::value, "list_contains_class doesn't work properly");
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static_assert(list_contains_class<int, char, int>::value, "list_contains_class doesn't work properly");
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static_assert(list_contains_class<int, int, char>::value, "list_contains_class doesn't work properly");
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static_assert(list_contains_class<int, char, int, char>::value, "list_contains_class doesn't work properly");
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static_assert(!list_contains_class<int, char, char>::value, "list_contains_class doesn't work properly");
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/**
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* @brief Construct a new fixed variant from an object that is legal in it by moving said object
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*
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* @tparam U A type that belongs in the list of types the variant supports
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* @param value The moved value
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*/
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template<typename U, std::enable_if_t<list_contains_class<gp::remove_cvref_t<U>,T...>::value,int> = 0>
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fixed_variant(U&& value)
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: index{r_index_of<gp::remove_cvref_t<U>, T...>::value}
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{
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using actual = gp::remove_cvref_t<U>;
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dtor = gp::function<void(void*)>([](void* thing){
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((actual*)thing)->~actual();
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}, nullopt);
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cpytor = gp::function<void(void*, void*)>([](void* src, void* dest){
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new(dest) actual(*(actual*)src);
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}, nullopt);
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mvtor = gp::function<void(void*, void*)>([](void* src, void* dest){
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new(dest) actual(gp::move(*(actual*)src));
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}, nullopt);
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mvtor((char*)&value, data);
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}
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fixed_variant(const fixed_variant& oth)
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: index{oth.index}
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, dtor{oth.dtor}
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, cpytor{oth.cpytor}
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, mvtor{oth.mvtor}
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{
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cpytor((char*)oth.data, (char*)data);
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}
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fixed_variant(fixed_variant& oth)
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: index{oth.index}
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, dtor{oth.dtor}
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, cpytor{oth.cpytor}
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, mvtor{oth.mvtor}
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{
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cpytor(oth.data, data);
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}
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fixed_variant(fixed_variant&& oth)
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: index{oth.index}
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, dtor{oth.dtor}
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, cpytor{oth.cpytor}
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, mvtor{oth.mvtor}
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{
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oth.index = std::numeric_limits<std::size_t>::max();
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mvtor(oth.data, data);
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}
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/**
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* @brief Gives an alternative (value usable in a switch statement) representing the given type
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*
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* @tparam U the type to match against
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* @return constexpr size_t a value that can be used in the case part of a switch case statement
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* @see type()
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*/
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template<typename U>
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constexpr static size_t alt() {
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return r_index_of<U, T...>::value;
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}
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/**
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* @brief Gives the type as can be matched in a switch statement using alternatives
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*
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* @return size_t a value that can be used in the switch part of a switch case statement
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* @see alt()
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*/
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size_t type() const {
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return index;
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}
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void operator=(fixed_variant& value)
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{
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if(index != std::numeric_limits<std::size_t>::max())
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{
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dtor((void*)data);
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}
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index = value.index;
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cpytor = value.cpytor;
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dtor = value.dtor;
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mvtor = value.mvtor;
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cpytor(value.data, data);
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}
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void operator=(fixed_variant&& value)
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{
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if(index != std::numeric_limits<std::size_t>::max())
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{
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dtor((void*)data);
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}
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dtor = value.dtor;
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cpytor = value.cpytor;
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mvtor = value.mvtor;
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index = value.index;
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value.index = std::numeric_limits<std::size_t>::max();
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mvtor(value.data, data);
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}
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template<typename U, typename std::enable_if<list_contains_class<U,T...>::value,int>::type>
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void operator=(U& value)
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{
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if(index != std::numeric_limits<std::size_t>::max())
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{
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dtor((void*)data);
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}
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index = r_index_of<gp::remove_cvref_t<U>, T...>::value;
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new(data) U(value);
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dtor = gp::function([](void* thing){((U*)thing)->~U();}, nullopt);
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cpytor = gp::function<void(void*, void*)>([](void* src, void* dest){new(dest) U(*(U*)src);}, nullopt);
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mvtor = gp::function<void(void*, void*)>([](void* src, void* dest){new(dest) U(gp::move(*(U*)src));}, nullopt);
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}
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template<typename U, typename std::enable_if<list_contains_class<U,T...>::value,int>::type>
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void operator=(U&& value)
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{
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if(index != std::numeric_limits<std::size_t>::max())
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{
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dtor((void*)data);
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}
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new(data) U(gp::move(value));
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index = r_index_of<gp::remove_cvref_t<U>, T...>::value;
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dtor = gp::function([](void* thing){((U*)thing)->~U();}, nullopt);
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cpytor = gp::function<void(void*, void*)>([](void* src, void* dest){new(dest) U(*(U*)src);}, nullopt);
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mvtor = gp::function<void(void*, void*)>([](void* src, void* dest){new(dest) U(gp::move(*(U*)src));}, nullopt);
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}
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~fixed_variant()
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{
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if(index != std::numeric_limits<std::size_t>::max() && dtor.ready())
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{
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dtor((void*)data);
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index = std::numeric_limits<std::size_t>::max();
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}
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}
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/**
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* @brief Brutally decay the variant into the given type.
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Will throw (@see bad_variant_access) if exceptions are enabled, else behaviour is undefined.
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*
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* @tparam U the type to decay towards
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* @return constexpr U& a decayed reference to the variant
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*/
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template<typename U>
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constexpr U& value()
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{
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if constexpr (gp_config::has_exceptions)
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{
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if(r_index_of<gp::remove_cvref_t<U>, T...>::value != index)
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{
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throw bad_variant_access<U>{};
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}
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}
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return *reinterpret_cast<U*>(data);
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}
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/**
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* @brief Tests if the variant is of a particular type.
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*
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* @tparam U the type to match against
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* @return true if the types match
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* @return false if the types don't match
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*/
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template<typename U>
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constexpr bool is_a()
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{
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if(r_index_of<gp::remove_cvref_t<U>, T...>::value == index)
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{
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return true;
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}
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else
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{
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return false;
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}
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}
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};
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}
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