65 lines
1.4 KiB
C++
65 lines
1.4 KiB
C++
#pragma once
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#include "variant.h"
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namespace meta
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{
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namespace detail
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{
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template<typename T>
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struct variant_helper;
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template<typename ... Ts>
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struct variant_helper<std::variant<Ts...>>
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{
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static constexpr auto ConstructJT()
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{
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using T = std::variant<Ts...>;
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return std::array<T(*)(), sizeof...(Ts)>
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{
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[]() -> T
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{
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return Ts{};
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} ...
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};
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}
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};
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}
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template<template<class T> typename Template, typename ...Ts>
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struct variant_wrap <std::variant<Ts...>, Template>
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{
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using type = std::variant<Template<Ts>...>;
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};
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template<typename ... Ts>
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struct tuple_to_variant <std::tuple<Ts...>>
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{
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using type = std::variant<Ts...>;
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};
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template<typename T>
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constexpr auto variant_construct(size_t i) noexcept
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{
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constexpr auto jt = detail::variant_helper<T>::ConstructJT();
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return jt[i]();
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}
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template<typename FindMe>
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struct index_in_variant<FindMe, std::variant<>>
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{
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static constexpr uint8_t value = 0;
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};
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template<typename FindMe, typename ... Ts>
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struct index_in_variant<FindMe, std::variant<FindMe, Ts...>>
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{
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static constexpr uint8_t value = 0;
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};
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template<typename FindMe, typename First, typename ... Ts>
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struct index_in_variant<FindMe, std::variant<First, Ts...>>
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{
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static constexpr uint8_t value = index_in_variant<FindMe, std::variant<Ts...>>::value + 1;
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};
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} |