summaryrefslogtreecommitdiffstats
path: root/depedencies/include/mpark/variant.hpp
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--depedencies/include/mpark/variant.hpp1827
1 files changed, 1827 insertions, 0 deletions
diff --git a/depedencies/include/mpark/variant.hpp b/depedencies/include/mpark/variant.hpp
new file mode 100644
index 0000000..3faecba
--- /dev/null
+++ b/depedencies/include/mpark/variant.hpp
@@ -0,0 +1,1827 @@
+// MPark.Variant
+//
+// Copyright Michael Park, 2015-2017
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+
+#ifndef MPARK_VARIANT_HPP
+#define MPARK_VARIANT_HPP
+
+/*
+ variant synopsis
+
+namespace std {
+
+ // 20.7.2, class template variant
+ template <class... Types>
+ class variant {
+ public:
+
+ // 20.7.2.1, constructors
+ constexpr variant() noexcept(see below);
+ variant(const variant&);
+ variant(variant&&) noexcept(see below);
+
+ template <class T> constexpr variant(T&&) noexcept(see below);
+
+ template <class T, class... Args>
+ constexpr explicit variant(in_place_type_t<T>, Args&&...);
+
+ template <class T, class U, class... Args>
+ constexpr explicit variant(
+ in_place_type_t<T>, initializer_list<U>, Args&&...);
+
+ template <size_t I, class... Args>
+ constexpr explicit variant(in_place_index_t<I>, Args&&...);
+
+ template <size_t I, class U, class... Args>
+ constexpr explicit variant(
+ in_place_index_t<I>, initializer_list<U>, Args&&...);
+
+ // 20.7.2.2, destructor
+ ~variant();
+
+ // 20.7.2.3, assignment
+ variant& operator=(const variant&);
+ variant& operator=(variant&&) noexcept(see below);
+
+ template <class T> variant& operator=(T&&) noexcept(see below);
+
+ // 20.7.2.4, modifiers
+ template <class T, class... Args>
+ T& emplace(Args&&...);
+
+ template <class T, class U, class... Args>
+ T& emplace(initializer_list<U>, Args&&...);
+
+ template <size_t I, class... Args>
+ variant_alternative<I, variant>& emplace(Args&&...);
+
+ template <size_t I, class U, class... Args>
+ variant_alternative<I, variant>& emplace(initializer_list<U>, Args&&...);
+
+ // 20.7.2.5, value status
+ constexpr bool valueless_by_exception() const noexcept;
+ constexpr size_t index() const noexcept;
+
+ // 20.7.2.6, swap
+ void swap(variant&) noexcept(see below);
+ };
+
+ // 20.7.3, variant helper classes
+ template <class T> struct variant_size; // undefined
+
+ template <class T>
+ constexpr size_t variant_size_v = variant_size<T>::value;
+
+ template <class T> struct variant_size<const T>;
+ template <class T> struct variant_size<volatile T>;
+ template <class T> struct variant_size<const volatile T>;
+
+ template <class... Types>
+ struct variant_size<variant<Types...>>;
+
+ template <size_t I, class T> struct variant_alternative; // undefined
+
+ template <size_t I, class T>
+ using variant_alternative_t = typename variant_alternative<I, T>::type;
+
+ template <size_t I, class T> struct variant_alternative<I, const T>;
+ template <size_t I, class T> struct variant_alternative<I, volatile T>;
+ template <size_t I, class T> struct variant_alternative<I, const volatile T>;
+
+ template <size_t I, class... Types>
+ struct variant_alternative<I, variant<Types...>>;
+
+ constexpr size_t variant_npos = -1;
+
+ // 20.7.4, value access
+ template <class T, class... Types>
+ constexpr bool holds_alternative(const variant<Types...>&) noexcept;
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>>&
+ get(variant<Types...>&);
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>>&&
+ get(variant<Types...>&&);
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>> const&
+ get(const variant<Types...>&);
+
+ template <size_t I, class... Types>
+ constexpr variant_alternative_t<I, variant<Types...>> const&&
+ get(const variant<Types...>&&);
+
+ template <class T, class... Types>
+ constexpr T& get(variant<Types...>&);
+
+ template <class T, class... Types>
+ constexpr T&& get(variant<Types...>&&);
+
+ template <class T, class... Types>
+ constexpr const T& get(const variant<Types...>&);
+
+ template <class T, class... Types>
+ constexpr const T&& get(const variant<Types...>&&);
+
+ template <size_t I, class... Types>
+ constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
+ get_if(variant<Types...>*) noexcept;
+
+ template <size_t I, class... Types>
+ constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
+ get_if(const variant<Types...>*) noexcept;
+
+ template <class T, class... Types>
+ constexpr add_pointer_t<T>
+ get_if(variant<Types...>*) noexcept;
+
+ template <class T, class... Types>
+ constexpr add_pointer_t<const T>
+ get_if(const variant<Types...>*) noexcept;
+
+ // 20.7.5, relational operators
+ template <class... Types>
+ constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
+
+ template <class... Types>
+ constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
+
+ // 20.7.6, visitation
+ template <class Visitor, class... Variants>
+ constexpr see below visit(Visitor&&, Variants&&...);
+
+ // 20.7.7, class monostate
+ struct monostate;
+
+ // 20.7.8, monostate relational operators
+ constexpr bool operator<(monostate, monostate) noexcept;
+ constexpr bool operator>(monostate, monostate) noexcept;
+ constexpr bool operator<=(monostate, monostate) noexcept;
+ constexpr bool operator>=(monostate, monostate) noexcept;
+ constexpr bool operator==(monostate, monostate) noexcept;
+ constexpr bool operator!=(monostate, monostate) noexcept;
+
+ // 20.7.9, specialized algorithms
+ template <class... Types>
+ void swap(variant<Types...>&, variant<Types...>&) noexcept(see below);
+
+ // 20.7.10, class bad_variant_access
+ class bad_variant_access;
+
+ // 20.7.11, hash support
+ template <class T> struct hash;
+ template <class... Types> struct hash<variant<Types...>>;
+ template <> struct hash<monostate>;
+
+} // namespace std
+
+*/
+
+#include <cstddef>
+#include <exception>
+#include <functional>
+#include <initializer_list>
+#include <new>
+#include <type_traits>
+#include <utility>
+
+#include "config.hpp"
+#include "in_place.hpp"
+#include "lib.hpp"
+
+namespace mpark {
+
+#ifdef MPARK_RETURN_TYPE_DEDUCTION
+
+#define AUTO auto
+#define AUTO_RETURN(...) { return __VA_ARGS__; }
+
+#define AUTO_REFREF auto &&
+#define AUTO_REFREF_RETURN(...) { return __VA_ARGS__; }
+
+#define DECLTYPE_AUTO decltype(auto)
+#define DECLTYPE_AUTO_RETURN(...) { return __VA_ARGS__; }
+
+#else
+
+#define AUTO auto
+#define AUTO_RETURN(...) \
+ -> lib::decay_t<decltype(__VA_ARGS__)> { return __VA_ARGS__; }
+
+#define AUTO_REFREF auto
+#define AUTO_REFREF_RETURN(...) \
+ -> decltype((__VA_ARGS__)) { \
+ static_assert(std::is_reference<decltype((__VA_ARGS__))>::value, ""); \
+ return __VA_ARGS__; \
+ }
+
+#define DECLTYPE_AUTO auto
+#define DECLTYPE_AUTO_RETURN(...) \
+ -> decltype(__VA_ARGS__) { return __VA_ARGS__; }
+
+#endif
+
+ class bad_variant_access : public std::exception {
+ public:
+ virtual const char *what() const noexcept { return "bad_variant_access"; }
+ };
+
+ [[noreturn]] inline void throw_bad_variant_access() {
+#ifdef MPARK_EXCEPTIONS
+ throw bad_variant_access{};
+#else
+ std::terminate();
+#endif
+ }
+
+ template <typename... Ts>
+ class variant;
+
+ template <typename T>
+ struct variant_size;
+
+#ifdef MPARK_VARIABLE_TEMPLATES
+ template <typename T>
+ constexpr std::size_t variant_size_v = variant_size<T>::value;
+#endif
+
+ template <typename T>
+ struct variant_size<const T> : variant_size<T> {};
+
+ template <typename T>
+ struct variant_size<volatile T> : variant_size<T> {};
+
+ template <typename T>
+ struct variant_size<const volatile T> : variant_size<T> {};
+
+ template <typename... Ts>
+ struct variant_size<variant<Ts...>> : lib::size_constant<sizeof...(Ts)> {};
+
+ template <std::size_t I, typename T>
+ struct variant_alternative;
+
+ template <std::size_t I, typename T>
+ using variant_alternative_t = typename variant_alternative<I, T>::type;
+
+ template <std::size_t I, typename T>
+ struct variant_alternative<I, const T>
+ : std::add_const<variant_alternative_t<I, T>> {};
+
+ template <std::size_t I, typename T>
+ struct variant_alternative<I, volatile T>
+ : std::add_volatile<variant_alternative_t<I, T>> {};
+
+ template <std::size_t I, typename T>
+ struct variant_alternative<I, const volatile T>
+ : std::add_cv<variant_alternative_t<I, T>> {};
+
+ template <std::size_t I, typename... Ts>
+ struct variant_alternative<I, variant<Ts...>> {
+ static_assert(I < sizeof...(Ts),
+ "Index out of bounds in std::variant_alternative<>");
+ using type = lib::type_pack_element_t<I, Ts...>;
+ };
+
+ constexpr std::size_t variant_npos = static_cast<std::size_t>(-1);
+
+ namespace detail {
+
+ inline constexpr bool all() { return true; }
+
+ template <typename... Bs>
+ inline constexpr bool all(bool b, Bs... bs) {
+ return b && all(bs...);
+ }
+
+ constexpr std::size_t not_found = static_cast<std::size_t>(-1);
+ constexpr std::size_t ambiguous = static_cast<std::size_t>(-2);
+
+#ifdef MPARK_CPP14_CONSTEXPR
+ template <typename T, typename... Ts>
+ inline constexpr std::size_t find_index() {
+ constexpr lib::array<bool, sizeof...(Ts)> matches = {
+ {std::is_same<T, Ts>::value...}
+ };
+ std::size_t result = not_found;
+ for (std::size_t i = 0; i < sizeof...(Ts); ++i) {
+ if (matches[i]) {
+ if (result != not_found) {
+ return ambiguous;
+ }
+ result = i;
+ }
+ }
+ return result;
+ }
+#else
+ inline constexpr std::size_t find_index_impl(std::size_t result,
+ std::size_t) {
+ return result;
+ }
+
+ template <typename... Bs>
+ inline constexpr std::size_t find_index_impl(std::size_t result,
+ std::size_t idx,
+ bool b,
+ Bs... bs) {
+ return b ? (result != not_found ? ambiguous
+ : find_index_impl(idx, idx + 1, bs...))
+ : find_index_impl(result, idx + 1, bs...);
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr std::size_t find_index() {
+ return find_index_impl(not_found, 0, std::is_same<T, Ts>::value...);
+ }
+#endif
+
+ template <std::size_t I>
+ using find_index_sfinae_impl =
+ lib::enable_if_t<I != not_found && I != ambiguous,
+ lib::size_constant<I>>;
+
+ template <typename T, typename... Ts>
+ using find_index_sfinae = find_index_sfinae_impl<find_index<T, Ts...>()>;
+
+ template <std::size_t I>
+ struct find_index_checked_impl : lib::size_constant<I> {
+ static_assert(I != not_found, "the specified type is not found.");
+ static_assert(I != ambiguous, "the specified type is ambiguous.");
+ };
+
+ template <typename T, typename... Ts>
+ using find_index_checked = find_index_checked_impl<find_index<T, Ts...>()>;
+
+ struct valueless_t {};
+
+ enum class Trait { TriviallyAvailable, Available, Unavailable };
+
+ template <typename T,
+ template <typename> class IsTriviallyAvailable,
+ template <typename> class IsAvailable>
+ inline constexpr Trait trait() {
+ return IsTriviallyAvailable<T>::value
+ ? Trait::TriviallyAvailable
+ : IsAvailable<T>::value ? Trait::Available
+ : Trait::Unavailable;
+ }
+
+#ifdef MPARK_CPP14_CONSTEXPR
+ template <typename... Traits>
+ inline constexpr Trait common_trait(Traits... traits) {
+ Trait result = Trait::TriviallyAvailable;
+ for (Trait t : {traits...}) {
+ if (static_cast<int>(t) > static_cast<int>(result)) {
+ result = t;
+ }
+ }
+ return result;
+ }
+#else
+ inline constexpr Trait common_trait_impl(Trait result) { return result; }
+
+ template <typename... Traits>
+ inline constexpr Trait common_trait_impl(Trait result,
+ Trait t,
+ Traits... ts) {
+ return static_cast<int>(t) > static_cast<int>(result)
+ ? common_trait_impl(t, ts...)
+ : common_trait_impl(result, ts...);
+ }
+
+ template <typename... Traits>
+ inline constexpr Trait common_trait(Traits... ts) {
+ return common_trait_impl(Trait::TriviallyAvailable, ts...);
+ }
+#endif
+
+ template <typename... Ts>
+ struct traits {
+ static constexpr Trait copy_constructible_trait =
+ common_trait(trait<Ts,
+ lib::is_trivially_copy_constructible,
+ std::is_copy_constructible>()...);
+
+ static constexpr Trait move_constructible_trait =
+ common_trait(trait<Ts,
+ lib::is_trivially_move_constructible,
+ std::is_move_constructible>()...);
+
+ static constexpr Trait copy_assignable_trait =
+ common_trait(copy_constructible_trait,
+ trait<Ts,
+ lib::is_trivially_copy_assignable,
+ std::is_copy_assignable>()...);
+
+ static constexpr Trait move_assignable_trait =
+ common_trait(move_constructible_trait,
+ trait<Ts,
+ lib::is_trivially_move_assignable,
+ std::is_move_assignable>()...);
+
+ static constexpr Trait destructible_trait =
+ common_trait(trait<Ts,
+ std::is_trivially_destructible,
+ std::is_destructible>()...);
+ };
+
+ namespace access {
+
+ struct recursive_union {
+#ifdef MPARK_RETURN_TYPE_DEDUCTION
+ template <typename V>
+ inline static constexpr auto &&get_alt(V &&v, in_place_index_t<0>) {
+ return lib::forward<V>(v).head_;
+ }
+
+ template <typename V, std::size_t I>
+ inline static constexpr auto &&get_alt(V &&v, in_place_index_t<I>) {
+ return get_alt(lib::forward<V>(v).tail_, in_place_index_t<I - 1>{});
+ }
+#else
+ template <std::size_t I, bool Dummy = true>
+ struct get_alt_impl {
+ template <typename V>
+ inline constexpr AUTO_REFREF operator()(V &&v) const
+ AUTO_REFREF_RETURN(get_alt_impl<I - 1>{}(lib::forward<V>(v).tail_))
+ };
+
+ template <bool Dummy>
+ struct get_alt_impl<0, Dummy> {
+ template <typename V>
+ inline constexpr AUTO_REFREF operator()(V &&v) const
+ AUTO_REFREF_RETURN(lib::forward<V>(v).head_)
+ };
+
+ template <typename V, std::size_t I>
+ inline static constexpr AUTO_REFREF get_alt(V &&v, in_place_index_t<I>)
+ AUTO_REFREF_RETURN(get_alt_impl<I>{}(lib::forward<V>(v)))
+#endif
+ };
+
+ struct base {
+ template <std::size_t I, typename V>
+ inline static constexpr AUTO_REFREF get_alt(V &&v)
+ AUTO_REFREF_RETURN(recursive_union::get_alt(
+ data(lib::forward<V>(v)), in_place_index_t<I>{}))
+ };
+
+ struct variant {
+ template <std::size_t I, typename V>
+ inline static constexpr AUTO_REFREF get_alt(V &&v)
+ AUTO_REFREF_RETURN(base::get_alt<I>(lib::forward<V>(v).impl_))
+ };
+
+ } // namespace access
+
+ namespace visitation {
+
+ struct base {
+ private:
+ template <typename T>
+ inline static constexpr const T &at(const T &elem) {
+ return elem;
+ }
+
+ template <typename T, std::size_t N, typename... Is>
+ inline static constexpr const lib::remove_all_extents_t<T> &at(
+ const lib::array<T, N> &elems, std::size_t i, Is... is) {
+ return at(elems[i], is...);
+ }
+
+ template <typename F, typename... Fs>
+ inline static constexpr int visit_visitor_return_type_check() {
+ static_assert(all(std::is_same<F, Fs>::value...),
+ "`mpark::visit` requires the visitor to have a single "
+ "return type.");
+ return 0;
+ }
+
+ template <typename... Fs>
+ inline static constexpr lib::array<
+ lib::common_type_t<lib::decay_t<Fs>...>,
+ sizeof...(Fs)>
+ make_farray(Fs &&... fs) {
+ using result = lib::array<lib::common_type_t<lib::decay_t<Fs>...>,
+ sizeof...(Fs)>;
+ return visit_visitor_return_type_check<lib::decay_t<Fs>...>(),
+ result{{lib::forward<Fs>(fs)...}};
+ }
+
+ template <std::size_t... Is>
+ struct dispatcher {
+ template <typename F, typename... Vs>
+ struct impl {
+ inline static constexpr DECLTYPE_AUTO dispatch(F f, Vs... vs)
+ DECLTYPE_AUTO_RETURN(lib::invoke(
+ static_cast<F>(f),
+ access::base::get_alt<Is>(static_cast<Vs>(vs))...))
+ };
+ };
+
+ template <typename F, typename... Vs, std::size_t... Is>
+ inline static constexpr AUTO make_dispatch(lib::index_sequence<Is...>)
+ AUTO_RETURN(&dispatcher<Is...>::template impl<F, Vs...>::dispatch)
+
+ template <std::size_t I, typename F, typename... Vs>
+ inline static constexpr AUTO make_fdiagonal_impl()
+ AUTO_RETURN(make_dispatch<F, Vs...>(
+ lib::index_sequence<lib::indexed_type<I, Vs>::value...>{}))
+
+ template <typename F, typename... Vs, std::size_t... Is>
+ inline static constexpr AUTO make_fdiagonal_impl(
+ lib::index_sequence<Is...>)
+ AUTO_RETURN(make_farray(make_fdiagonal_impl<Is, F, Vs...>()...))
+
+ template <typename F, typename V, typename... Vs>
+ inline static constexpr /* auto * */ auto make_fdiagonal()
+ -> decltype(make_fdiagonal_impl<F, V, Vs...>(
+ lib::make_index_sequence<lib::decay_t<V>::size()>{})) {
+ static_assert(
+ all((lib::decay_t<V>::size() == lib::decay_t<Vs>::size())...),
+ "all of the variants must be the same size.");
+ return make_fdiagonal_impl<F, V, Vs...>(
+ lib::make_index_sequence<lib::decay_t<V>::size()>{});
+ }
+
+#ifdef MPARK_RETURN_TYPE_DEDUCTION
+ template <typename F, typename... Vs, std::size_t... Is>
+ inline static constexpr auto make_fmatrix_impl(
+ lib::index_sequence<Is...> is) {
+ return make_dispatch<F, Vs...>(is);
+ }
+
+ template <typename F,
+ typename... Vs,
+ std::size_t... Is,
+ std::size_t... Js,
+ typename... Ls>
+ inline static constexpr auto make_fmatrix_impl(
+ lib::index_sequence<Is...>, lib::index_sequence<Js...>, Ls... ls) {
+ return make_farray(make_fmatrix_impl<F, Vs...>(
+ lib::index_sequence<Is..., Js>{}, ls...)...);
+ }
+
+ template <typename F, typename... Vs>
+ inline static constexpr auto make_fmatrix() {
+ return make_fmatrix_impl<F, Vs...>(
+ lib::index_sequence<>{},
+ lib::make_index_sequence<lib::decay_t<Vs>::size()>{}...);
+ }
+#else
+ template <typename F, typename... Vs>
+ struct make_fmatrix_impl {
+ template <typename...>
+ struct impl;
+
+ template <std::size_t... Is>
+ struct impl<lib::index_sequence<Is...>> {
+ inline constexpr AUTO operator()() const
+ AUTO_RETURN(
+ make_dispatch<F, Vs...>(lib::index_sequence<Is...>{}))
+ };
+
+ template <std::size_t... Is, std::size_t... Js, typename... Ls>
+ struct impl<lib::index_sequence<Is...>,
+ lib::index_sequence<Js...>,
+ Ls...> {
+ inline constexpr AUTO operator()() const
+ AUTO_RETURN(make_farray(
+ impl<lib::index_sequence<Is..., Js>, Ls...>{}()...))
+ };
+ };
+
+ template <typename F, typename... Vs>
+ inline static constexpr AUTO make_fmatrix()
+ AUTO_RETURN(
+ typename make_fmatrix_impl<F, Vs...>::template impl<
+ lib::index_sequence<>,
+ lib::make_index_sequence<lib::decay_t<Vs>::size()>...>{}())
+#endif
+
+ public:
+ template <typename Visitor, typename... Vs>
+ inline static constexpr DECLTYPE_AUTO visit_alt_at(std::size_t index,
+ Visitor &&visitor,
+ Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(
+ at(make_fdiagonal<Visitor &&,
+ decltype(as_base(lib::forward<Vs>(vs)))...>(),
+ index)(lib::forward<Visitor>(visitor),
+ as_base(lib::forward<Vs>(vs))...))
+
+ template <typename Visitor, typename... Vs>
+ inline static constexpr DECLTYPE_AUTO visit_alt(Visitor &&visitor,
+ Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(
+ at(make_fmatrix<Visitor &&,
+ decltype(as_base(lib::forward<Vs>(vs)))...>(),
+ vs.index()...)(lib::forward<Visitor>(visitor),
+ as_base(lib::forward<Vs>(vs))...))
+ };
+
+ struct variant {
+ private:
+ template <typename Visitor, typename... Values>
+ struct visit_exhaustive_visitor_check {
+ static_assert(
+ lib::is_invocable<Visitor, Values...>::value,
+ "`mpark::visit` requires the visitor to be exhaustive.");
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4100)
+#endif
+ inline constexpr DECLTYPE_AUTO operator()(Visitor &&visitor,
+ Values &&... values) const
+ DECLTYPE_AUTO_RETURN(lib::invoke(lib::forward<Visitor>(visitor),
+ lib::forward<Values>(values)...))
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+ };
+
+ template <typename Visitor>
+ struct value_visitor {
+ Visitor &&visitor_;
+
+ template <typename... Alts>
+ inline constexpr DECLTYPE_AUTO operator()(Alts &&... alts) const
+ DECLTYPE_AUTO_RETURN(
+ visit_exhaustive_visitor_check<
+ Visitor,
+ decltype((lib::forward<Alts>(alts).value))...>{}(
+ lib::forward<Visitor>(visitor_),
+ lib::forward<Alts>(alts).value...))
+ };
+
+ template <typename Visitor>
+ inline static constexpr AUTO make_value_visitor(Visitor &&visitor)
+ AUTO_RETURN(value_visitor<Visitor>{lib::forward<Visitor>(visitor)})
+
+ public:
+ template <typename Visitor, typename... Vs>
+ inline static constexpr DECLTYPE_AUTO visit_alt_at(std::size_t index,
+ Visitor &&visitor,
+ Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(
+ base::visit_alt_at(index,
+ lib::forward<Visitor>(visitor),
+ lib::forward<Vs>(vs).impl_...))
+
+ template <typename Visitor, typename... Vs>
+ inline static constexpr DECLTYPE_AUTO visit_alt(Visitor &&visitor,
+ Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(base::visit_alt(lib::forward<Visitor>(visitor),
+ lib::forward<Vs>(vs).impl_...))
+
+ template <typename Visitor, typename... Vs>
+ inline static constexpr DECLTYPE_AUTO visit_value_at(std::size_t index,
+ Visitor &&visitor,
+ Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(
+ visit_alt_at(index,
+ make_value_visitor(lib::forward<Visitor>(visitor)),
+ lib::forward<Vs>(vs)...))
+
+ template <typename Visitor, typename... Vs>
+ inline static constexpr DECLTYPE_AUTO visit_value(Visitor &&visitor,
+ Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(
+ visit_alt(make_value_visitor(lib::forward<Visitor>(visitor)),
+ lib::forward<Vs>(vs)...))
+ };
+
+ } // namespace visitation
+
+ template <std::size_t Index, typename T>
+ struct alt {
+ using value_type = T;
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4244)
+#endif
+ template <typename... Args>
+ inline explicit constexpr alt(in_place_t, Args &&... args)
+ : value(lib::forward<Args>(args)...) {}
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+ T value;
+ };
+
+ template <Trait DestructibleTrait, std::size_t Index, typename... Ts>
+ union recursive_union;
+
+ template <Trait DestructibleTrait, std::size_t Index>
+ union recursive_union<DestructibleTrait, Index> {};
+
+#define MPARK_VARIANT_RECURSIVE_UNION(destructible_trait, destructor) \
+ template <std::size_t Index, typename T, typename... Ts> \
+ union recursive_union<destructible_trait, Index, T, Ts...> { \
+ public: \
+ inline explicit constexpr recursive_union(valueless_t) noexcept \
+ : dummy_{} {} \
+ \
+ template <typename... Args> \
+ inline explicit constexpr recursive_union(in_place_index_t<0>, \
+ Args &&... args) \
+ : head_(in_place_t{}, lib::forward<Args>(args)...) {} \
+ \
+ template <std::size_t I, typename... Args> \
+ inline explicit constexpr recursive_union(in_place_index_t<I>, \
+ Args &&... args) \
+ : tail_(in_place_index_t<I - 1>{}, lib::forward<Args>(args)...) {} \
+ \
+ recursive_union(const recursive_union &) = default; \
+ recursive_union(recursive_union &&) = default; \
+ \
+ destructor \
+ \
+ recursive_union &operator=(const recursive_union &) = default; \
+ recursive_union &operator=(recursive_union &&) = default; \
+ \
+ private: \
+ char dummy_; \
+ alt<Index, T> head_; \
+ recursive_union<destructible_trait, Index + 1, Ts...> tail_; \
+ \
+ friend struct access::recursive_union; \
+ }
+
+ MPARK_VARIANT_RECURSIVE_UNION(Trait::TriviallyAvailable,
+ ~recursive_union() = default;);
+ MPARK_VARIANT_RECURSIVE_UNION(Trait::Available,
+ ~recursive_union() {});
+ MPARK_VARIANT_RECURSIVE_UNION(Trait::Unavailable,
+ ~recursive_union() = delete;);
+
+#undef MPARK_VARIANT_RECURSIVE_UNION
+
+ using index_t = unsigned int;
+
+ template <Trait DestructibleTrait, typename... Ts>
+ class base {
+ public:
+ inline explicit constexpr base(valueless_t tag) noexcept
+ : data_(tag), index_(static_cast<index_t>(-1)) {}
+
+ template <std::size_t I, typename... Args>
+ inline explicit constexpr base(in_place_index_t<I>, Args &&... args)
+ : data_(in_place_index_t<I>{}, lib::forward<Args>(args)...),
+ index_(I) {}
+
+ inline constexpr bool valueless_by_exception() const noexcept {
+ return index_ == static_cast<index_t>(-1);
+ }
+
+ inline constexpr std::size_t index() const noexcept {
+ return valueless_by_exception() ? variant_npos : index_;
+ }
+
+ protected:
+ using data_t = recursive_union<DestructibleTrait, 0, Ts...>;
+
+ friend inline constexpr base &as_base(base &b) { return b; }
+ friend inline constexpr const base &as_base(const base &b) { return b; }
+ friend inline constexpr base &&as_base(base &&b) { return lib::move(b); }
+ friend inline constexpr const base &&as_base(const base &&b) { return lib::move(b); }
+
+ friend inline constexpr data_t &data(base &b) { return b.data_; }
+ friend inline constexpr const data_t &data(const base &b) { return b.data_; }
+ friend inline constexpr data_t &&data(base &&b) { return lib::move(b).data_; }
+ friend inline constexpr const data_t &&data(const base &&b) { return lib::move(b).data_; }
+
+ inline static constexpr std::size_t size() { return sizeof...(Ts); }
+
+ data_t data_;
+ index_t index_;
+
+ friend struct access::base;
+ friend struct visitation::base;
+ };
+
+ struct dtor {
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4100)
+#endif
+ template <typename Alt>
+ inline void operator()(Alt &alt) const noexcept { alt.~Alt(); }
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+ };
+
+#if defined(_MSC_VER) && _MSC_VER < 1910
+#define INHERITING_CTOR(type, base) \
+ template <typename... Args> \
+ inline explicit constexpr type(Args &&... args) \
+ : base(lib::forward<Args>(args)...) {}
+#else
+#define INHERITING_CTOR(type, base) using base::base;
+#endif
+
+ template <typename Traits, Trait = Traits::destructible_trait>
+ class destructor;
+
+#define MPARK_VARIANT_DESTRUCTOR(destructible_trait, definition, destroy) \
+ template <typename... Ts> \
+ class destructor<traits<Ts...>, destructible_trait> \
+ : public base<destructible_trait, Ts...> { \
+ using super = base<destructible_trait, Ts...>; \
+ \
+ public: \
+ INHERITING_CTOR(destructor, super) \
+ using super::operator=; \
+ \
+ destructor(const destructor &) = default; \
+ destructor(destructor &&) = default; \
+ definition \
+ destructor &operator=(const destructor &) = default; \
+ destructor &operator=(destructor &&) = default; \
+ \
+ protected: \
+ destroy \
+ }
+
+ MPARK_VARIANT_DESTRUCTOR(
+ Trait::TriviallyAvailable,
+ ~destructor() = default;,
+ inline void destroy() noexcept {
+ this->index_ = static_cast<index_t>(-1);
+ });
+
+ MPARK_VARIANT_DESTRUCTOR(
+ Trait::Available,
+ ~destructor() { destroy(); },
+ inline void destroy() noexcept {
+ if (!this->valueless_by_exception()) {
+ visitation::base::visit_alt(dtor{}, *this);
+ }
+ this->index_ = static_cast<index_t>(-1);
+ });
+
+ MPARK_VARIANT_DESTRUCTOR(
+ Trait::Unavailable,
+ ~destructor() = delete;,
+ inline void destroy() noexcept = delete;);
+
+#undef MPARK_VARIANT_DESTRUCTOR
+
+ template <typename Traits>
+ class constructor : public destructor<Traits> {
+ using super = destructor<Traits>;
+
+ public:
+ INHERITING_CTOR(constructor, super)
+ using super::operator=;
+
+ protected:
+#ifndef MPARK_GENERIC_LAMBDAS
+ struct ctor {
+ template <typename LhsAlt, typename RhsAlt>
+ inline void operator()(LhsAlt &lhs_alt, RhsAlt &&rhs_alt) const {
+ constructor::construct_alt(lhs_alt,
+ lib::forward<RhsAlt>(rhs_alt).value);
+ }
+ };
+#endif
+
+ template <std::size_t I, typename T, typename... Args>
+ inline static T &construct_alt(alt<I, T> &a, Args &&... args) {
+ ::new (static_cast<void *>(lib::addressof(a)))
+ alt<I, T>(in_place_t{}, lib::forward<Args>(args)...);
+ return a.value;
+ }
+
+ template <typename Rhs>
+ inline static void generic_construct(constructor &lhs, Rhs &&rhs) {
+ lhs.destroy();
+ if (!rhs.valueless_by_exception()) {
+ visitation::base::visit_alt_at(
+ rhs.index(),
+#ifdef MPARK_GENERIC_LAMBDAS
+ [](auto &lhs_alt, auto &&rhs_alt) {
+ constructor::construct_alt(
+ lhs_alt, lib::forward<decltype(rhs_alt)>(rhs_alt).value);
+ }
+#else
+ ctor{}
+#endif
+ ,
+ lhs,
+ lib::forward<Rhs>(rhs));
+ lhs.index_ = rhs.index_;
+ }
+ }
+ };
+
+ template <typename Traits, Trait = Traits::move_constructible_trait>
+ class move_constructor;
+
+#define MPARK_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, definition) \
+ template <typename... Ts> \
+ class move_constructor<traits<Ts...>, move_constructible_trait> \
+ : public constructor<traits<Ts...>> { \
+ using super = constructor<traits<Ts...>>; \
+ \
+ public: \
+ INHERITING_CTOR(move_constructor, super) \
+ using super::operator=; \
+ \
+ move_constructor(const move_constructor &) = default; \
+ definition \
+ ~move_constructor() = default; \
+ move_constructor &operator=(const move_constructor &) = default; \
+ move_constructor &operator=(move_constructor &&) = default; \
+ }
+
+ MPARK_VARIANT_MOVE_CONSTRUCTOR(
+ Trait::TriviallyAvailable,
+ move_constructor(move_constructor &&that) = default;);
+
+ MPARK_VARIANT_MOVE_CONSTRUCTOR(
+ Trait::Available,
+ move_constructor(move_constructor &&that) noexcept(
+ all(std::is_nothrow_move_constructible<Ts>::value...))
+ : move_constructor(valueless_t{}) {
+ this->generic_construct(*this, lib::move(that));
+ });
+
+ MPARK_VARIANT_MOVE_CONSTRUCTOR(
+ Trait::Unavailable,
+ move_constructor(move_constructor &&) = delete;);
+
+#undef MPARK_VARIANT_MOVE_CONSTRUCTOR
+
+ template <typename Traits, Trait = Traits::copy_constructible_trait>
+ class copy_constructor;
+
+#define MPARK_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, definition) \
+ template <typename... Ts> \
+ class copy_constructor<traits<Ts...>, copy_constructible_trait> \
+ : public move_constructor<traits<Ts...>> { \
+ using super = move_constructor<traits<Ts...>>; \
+ \
+ public: \
+ INHERITING_CTOR(copy_constructor, super) \
+ using super::operator=; \
+ \
+ definition \
+ copy_constructor(copy_constructor &&) = default; \
+ ~copy_constructor() = default; \
+ copy_constructor &operator=(const copy_constructor &) = default; \
+ copy_constructor &operator=(copy_constructor &&) = default; \
+ }
+
+ MPARK_VARIANT_COPY_CONSTRUCTOR(
+ Trait::TriviallyAvailable,
+ copy_constructor(const copy_constructor &that) = default;);
+
+ MPARK_VARIANT_COPY_CONSTRUCTOR(
+ Trait::Available,
+ copy_constructor(const copy_constructor &that)
+ : copy_constructor(valueless_t{}) {
+ this->generic_construct(*this, that);
+ });
+
+ MPARK_VARIANT_COPY_CONSTRUCTOR(
+ Trait::Unavailable,
+ copy_constructor(const copy_constructor &) = delete;);
+
+#undef MPARK_VARIANT_COPY_CONSTRUCTOR
+
+ template <typename Traits>
+ class assignment : public copy_constructor<Traits> {
+ using super = copy_constructor<Traits>;
+
+ public:
+ INHERITING_CTOR(assignment, super)
+ using super::operator=;
+
+ template <std::size_t I, typename... Args>
+ inline /* auto & */ auto emplace(Args &&... args)
+ -> decltype(this->construct_alt(access::base::get_alt<I>(*this),
+ lib::forward<Args>(args)...)) {
+ this->destroy();
+ auto &result = this->construct_alt(access::base::get_alt<I>(*this),
+ lib::forward<Args>(args)...);
+ this->index_ = I;
+ return result;
+ }
+
+ protected:
+#ifndef MPARK_GENERIC_LAMBDAS
+ template <typename That>
+ struct assigner {
+ template <typename ThisAlt, typename ThatAlt>
+ inline void operator()(ThisAlt &this_alt, ThatAlt &&that_alt) const {
+ self->assign_alt(this_alt, lib::forward<ThatAlt>(that_alt).value);
+ }
+ assignment *self;
+ };
+#endif
+
+ template <std::size_t I, typename T, typename Arg>
+ inline void assign_alt(alt<I, T> &a, Arg &&arg) {
+ if (this->index() == I) {
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4244)
+#endif
+ a.value = lib::forward<Arg>(arg);
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+ } else {
+ struct {
+ void operator()(std::true_type) const {
+ this_->emplace<I>(lib::forward<Arg>(arg_));
+ }
+ void operator()(std::false_type) const {
+ this_->emplace<I>(T(lib::forward<Arg>(arg_)));
+ }
+ assignment *this_;
+ Arg &&arg_;
+ } impl{this, lib::forward<Arg>(arg)};
+ impl(lib::bool_constant<
+ std::is_nothrow_constructible<T, Arg>::value ||
+ !std::is_nothrow_move_constructible<T>::value>{});
+ }
+ }
+
+ template <typename That>
+ inline void generic_assign(That &&that) {
+ if (this->valueless_by_exception() && that.valueless_by_exception()) {
+ // do nothing.
+ } else if (that.valueless_by_exception()) {
+ this->destroy();
+ } else {
+ visitation::base::visit_alt_at(
+ that.index(),
+#ifdef MPARK_GENERIC_LAMBDAS
+ [this](auto &this_alt, auto &&that_alt) {
+ this->assign_alt(
+ this_alt, lib::forward<decltype(that_alt)>(that_alt).value);
+ }
+#else
+ assigner<That>{this}
+#endif
+ ,
+ *this,
+ lib::forward<That>(that));
+ }
+ }
+ };
+
+ template <typename Traits, Trait = Traits::move_assignable_trait>
+ class move_assignment;
+
+#define MPARK_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, definition) \
+ template <typename... Ts> \
+ class move_assignment<traits<Ts...>, move_assignable_trait> \
+ : public assignment<traits<Ts...>> { \
+ using super = assignment<traits<Ts...>>; \
+ \
+ public: \
+ INHERITING_CTOR(move_assignment, super) \
+ using super::operator=; \
+ \
+ move_assignment(const move_assignment &) = default; \
+ move_assignment(move_assignment &&) = default; \
+ ~move_assignment() = default; \
+ move_assignment &operator=(const move_assignment &) = default; \
+ definition \
+ }
+
+ MPARK_VARIANT_MOVE_ASSIGNMENT(
+ Trait::TriviallyAvailable,
+ move_assignment &operator=(move_assignment &&that) = default;);
+
+ MPARK_VARIANT_MOVE_ASSIGNMENT(
+ Trait::Available,
+ move_assignment &
+ operator=(move_assignment &&that) noexcept(
+ all((std::is_nothrow_move_constructible<Ts>::value &&
+ std::is_nothrow_move_assignable<Ts>::value)...)) {
+ this->generic_assign(lib::move(that));
+ return *this;
+ });
+
+ MPARK_VARIANT_MOVE_ASSIGNMENT(
+ Trait::Unavailable,
+ move_assignment &operator=(move_assignment &&) = delete;);
+
+#undef MPARK_VARIANT_MOVE_ASSIGNMENT
+
+ template <typename Traits, Trait = Traits::copy_assignable_trait>
+ class copy_assignment;
+
+#define MPARK_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, definition) \
+ template <typename... Ts> \
+ class copy_assignment<traits<Ts...>, copy_assignable_trait> \
+ : public move_assignment<traits<Ts...>> { \
+ using super = move_assignment<traits<Ts...>>; \
+ \
+ public: \
+ INHERITING_CTOR(copy_assignment, super) \
+ using super::operator=; \
+ \
+ copy_assignment(const copy_assignment &) = default; \
+ copy_assignment(copy_assignment &&) = default; \
+ ~copy_assignment() = default; \
+ definition \
+ copy_assignment &operator=(copy_assignment &&) = default; \
+ }
+
+ MPARK_VARIANT_COPY_ASSIGNMENT(
+ Trait::TriviallyAvailable,
+ copy_assignment &operator=(const copy_assignment &that) = default;);
+
+ MPARK_VARIANT_COPY_ASSIGNMENT(
+ Trait::Available,
+ copy_assignment &operator=(const copy_assignment &that) {
+ this->generic_assign(that);
+ return *this;
+ });
+
+ MPARK_VARIANT_COPY_ASSIGNMENT(
+ Trait::Unavailable,
+ copy_assignment &operator=(const copy_assignment &) = delete;);
+
+#undef MPARK_VARIANT_COPY_ASSIGNMENT
+
+ template <typename... Ts>
+ class impl : public copy_assignment<traits<Ts...>> {
+ using super = copy_assignment<traits<Ts...>>;
+
+ public:
+ INHERITING_CTOR(impl, super)
+ using super::operator=;
+
+ template <std::size_t I, typename Arg>
+ inline void assign(Arg &&arg) {
+ this->assign_alt(access::base::get_alt<I>(*this),
+ lib::forward<Arg>(arg));
+ }
+
+ inline void swap(impl &that) {
+ if (this->valueless_by_exception() && that.valueless_by_exception()) {
+ // do nothing.
+ } else if (this->index() == that.index()) {
+ visitation::base::visit_alt_at(this->index(),
+#ifdef MPARK_GENERIC_LAMBDAS
+ [](auto &this_alt, auto &that_alt) {
+ using std::swap;
+ swap(this_alt.value,
+ that_alt.value);
+ }
+#else
+ swapper{}
+#endif
+ ,
+ *this,
+ that);
+ } else {
+ impl *lhs = this;
+ impl *rhs = lib::addressof(that);
+ if (lhs->move_nothrow() && !rhs->move_nothrow()) {
+ std::swap(lhs, rhs);
+ }
+ impl tmp(lib::move(*rhs));
+#ifdef MPARK_EXCEPTIONS
+ // EXTENSION: When the move construction of `lhs` into `rhs` throws
+ // and `tmp` is nothrow move constructible then we move `tmp` back
+ // into `rhs` and provide the strong exception safety guarantee.
+ try {
+ this->generic_construct(*rhs, lib::move(*lhs));
+ } catch (...) {
+ if (tmp.move_nothrow()) {
+ this->generic_construct(*rhs, lib::move(tmp));
+ }
+ throw;
+ }
+#else
+ this->generic_construct(*rhs, lib::move(*lhs));
+#endif
+ this->generic_construct(*lhs, lib::move(tmp));
+ }
+ }
+
+ private:
+#ifndef MPARK_GENERIC_LAMBDAS
+ struct swapper {
+ template <typename ThisAlt, typename ThatAlt>
+ inline void operator()(ThisAlt &this_alt, ThatAlt &that_alt) const {
+ using std::swap;
+ swap(this_alt.value, that_alt.value);
+ }
+ };
+#endif
+
+ inline constexpr bool move_nothrow() const {
+ return this->valueless_by_exception() ||
+ lib::array<bool, sizeof...(Ts)>{
+ {std::is_nothrow_move_constructible<Ts>::value...}
+ }[this->index()];
+ }
+ };
+
+ template <typename... Ts>
+ struct overload;
+
+ template <>
+ struct overload<> { void operator()() const {} };
+
+ template <typename T, typename... Ts>
+ struct overload<T, Ts...> : overload<Ts...> {
+ using overload<Ts...>::operator();
+ lib::identity<T> operator()(T) const { return {}; }
+ };
+
+ template <typename T, typename... Ts>
+ using best_match_t =
+ typename lib::invoke_result_t<overload<Ts...>, T &&>::type;
+
+ template <typename T>
+ struct is_in_place_index : std::false_type {};
+
+ template <std::size_t I>
+ struct is_in_place_index<in_place_index_t<I>> : std::true_type {};
+
+ template <typename T>
+ struct is_in_place_type : std::false_type {};
+
+ template <typename T>
+ struct is_in_place_type<in_place_type_t<T>> : std::true_type {};
+
+ } // detail
+
+ template <typename... Ts>
+ class variant {
+ static_assert(0 < sizeof...(Ts),
+ "variant must consist of at least one alternative.");
+
+ static_assert(lib::all<!std::is_array<Ts>::value...>::value,
+ "variant can not have an array type as an alternative.");
+
+ static_assert(lib::all<!std::is_reference<Ts>::value...>::value,
+ "variant can not have a reference type as an alternative.");
+
+ static_assert(lib::all<!std::is_void<Ts>::value...>::value,
+ "variant can not have a void type as an alternative.");
+
+ public:
+ template <
+ typename Front = lib::type_pack_element_t<0, Ts...>,
+ lib::enable_if_t<std::is_default_constructible<Front>::value, int> = 0>
+ inline constexpr variant() noexcept(
+ std::is_nothrow_default_constructible<Front>::value)
+ : impl_(in_place_index_t<0>{}) {}
+
+ variant(const variant &) = default;
+ variant(variant &&) = default;
+
+ template <
+ typename Arg,
+ typename Decayed = lib::decay_t<Arg>,
+ lib::enable_if_t<!std::is_same<Decayed, variant>::value, int> = 0,
+ lib::enable_if_t<!detail::is_in_place_index<Decayed>::value, int> = 0,
+ lib::enable_if_t<!detail::is_in_place_type<Decayed>::value, int> = 0,
+ typename T = detail::best_match_t<Arg, Ts...>,
+ std::size_t I = detail::find_index_sfinae<T, Ts...>::value,
+ lib::enable_if_t<std::is_constructible<T, Arg>::value, int> = 0>
+ inline constexpr variant(Arg &&arg) noexcept(
+ std::is_nothrow_constructible<T, Arg>::value)
+ : impl_(in_place_index_t<I>{}, lib::forward<Arg>(arg)) {}
+
+ template <
+ std::size_t I,
+ typename... Args,
+ typename T = lib::type_pack_element_t<I, Ts...>,
+ lib::enable_if_t<std::is_constructible<T, Args...>::value, int> = 0>
+ inline explicit constexpr variant(
+ in_place_index_t<I>,
+ Args &&... args) noexcept(std::is_nothrow_constructible<T,
+ Args...>::value)
+ : impl_(in_place_index_t<I>{}, lib::forward<Args>(args)...) {}
+
+ template <
+ std::size_t I,
+ typename Up,
+ typename... Args,
+ typename T = lib::type_pack_element_t<I, Ts...>,
+ lib::enable_if_t<std::is_constructible<T,
+ std::initializer_list<Up> &,
+ Args...>::value,
+ int> = 0>
+ inline explicit constexpr variant(
+ in_place_index_t<I>,
+ std::initializer_list<Up> il,
+ Args &&... args) noexcept(std::
+ is_nothrow_constructible<
+ T,
+ std::initializer_list<Up> &,
+ Args...>::value)
+ : impl_(in_place_index_t<I>{}, il, lib::forward<Args>(args)...) {}
+
+ template <
+ typename T,
+ typename... Args,
+ std::size_t I = detail::find_index_sfinae<T, Ts...>::value,
+ lib::enable_if_t<std::is_constructible<T, Args...>::value, int> = 0>
+ inline explicit constexpr variant(
+ in_place_type_t<T>,
+ Args &&... args) noexcept(std::is_nothrow_constructible<T,
+ Args...>::value)
+ : impl_(in_place_index_t<I>{}, lib::forward<Args>(args)...) {}
+
+ template <
+ typename T,
+ typename Up,
+ typename... Args,
+ std::size_t I = detail::find_index_sfinae<T, Ts...>::value,
+ lib::enable_if_t<std::is_constructible<T,
+ std::initializer_list<Up> &,
+ Args...>::value,
+ int> = 0>
+ inline explicit constexpr variant(
+ in_place_type_t<T>,
+ std::initializer_list<Up> il,
+ Args &&... args) noexcept(std::
+ is_nothrow_constructible<
+ T,
+ std::initializer_list<Up> &,
+ Args...>::value)
+ : impl_(in_place_index_t<I>{}, il, lib::forward<Args>(args)...) {}
+
+ ~variant() = default;
+
+ variant &operator=(const variant &) = default;
+ variant &operator=(variant &&) = default;
+
+ template <typename Arg,
+ lib::enable_if_t<!std::is_same<lib::decay_t<Arg>, variant>::value,
+ int> = 0,
+ typename T = detail::best_match_t<Arg, Ts...>,
+ std::size_t I = detail::find_index_sfinae<T, Ts...>::value,
+ lib::enable_if_t<(std::is_assignable<T &, Arg>::value &&
+ std::is_constructible<T, Arg>::value),
+ int> = 0>
+ inline variant &operator=(Arg &&arg) noexcept(
+ (std::is_nothrow_assignable<T &, Arg>::value &&
+ std::is_nothrow_constructible<T, Arg>::value)) {
+ impl_.template assign<I>(lib::forward<Arg>(arg));
+ return *this;
+ }
+
+ template <
+ std::size_t I,
+ typename... Args,
+ typename T = lib::type_pack_element_t<I, Ts...>,
+ lib::enable_if_t<std::is_constructible<T, Args...>::value, int> = 0>
+ inline T &emplace(Args &&... args) {
+ return impl_.template emplace<I>(lib::forward<Args>(args)...);
+ }
+
+ template <
+ std::size_t I,
+ typename Up,
+ typename... Args,
+ typename T = lib::type_pack_element_t<I, Ts...>,
+ lib::enable_if_t<std::is_constructible<T,
+ std::initializer_list<Up> &,
+ Args...>::value,
+ int> = 0>
+ inline T &emplace(std::initializer_list<Up> il, Args &&... args) {
+ return impl_.template emplace<I>(il, lib::forward<Args>(args)...);
+ }
+
+ template <
+ typename T,
+ typename... Args,
+ std::size_t I = detail::find_index_sfinae<T, Ts...>::value,
+ lib::enable_if_t<std::is_constructible<T, Args...>::value, int> = 0>
+ inline T &emplace(Args &&... args) {
+ return impl_.template emplace<I>(lib::forward<Args>(args)...);
+ }
+
+ template <
+ typename T,
+ typename Up,
+ typename... Args,
+ std::size_t I = detail::find_index_sfinae<T, Ts...>::value,
+ lib::enable_if_t<std::is_constructible<T,
+ std::initializer_list<Up> &,
+ Args...>::value,
+ int> = 0>
+ inline T &emplace(std::initializer_list<Up> il, Args &&... args) {
+ return impl_.template emplace<I>(il, lib::forward<Args>(args)...);
+ }
+
+ inline constexpr bool valueless_by_exception() const noexcept {
+ return impl_.valueless_by_exception();
+ }
+
+ inline constexpr std::size_t index() const noexcept {
+ return impl_.index();
+ }
+
+ template <
+ bool Dummy = true,
+ lib::enable_if_t<lib::all<Dummy,
+ (std::is_move_constructible<Ts>::value &&
+ lib::is_swappable<Ts>::value)...>::value,
+ int> = 0>
+ inline void swap(variant &that) noexcept(
+ lib::all<(std::is_nothrow_move_constructible<Ts>::value &&
+ lib::is_nothrow_swappable<Ts>::value)...>::value) {
+ impl_.swap(that.impl_);
+ }
+
+ private:
+ detail::impl<Ts...> impl_;
+
+ friend struct detail::access::variant;
+ friend struct detail::visitation::variant;
+ };
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr bool holds_alternative(const variant<Ts...> &v) noexcept {
+ return v.index() == I;
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr bool holds_alternative(const variant<Ts...> &v) noexcept {
+ return holds_alternative<detail::find_index_checked<T, Ts...>::value>(v);
+ }
+
+ namespace detail {
+ template <std::size_t I, typename V>
+ struct generic_get_impl {
+ constexpr generic_get_impl(int) {}
+
+ constexpr AUTO_REFREF operator()(V &&v) const
+ AUTO_REFREF_RETURN(
+ access::variant::get_alt<I>(lib::forward<V>(v)).value)
+ };
+
+ template <std::size_t I, typename V>
+ inline constexpr AUTO_REFREF generic_get(V &&v)
+ AUTO_REFREF_RETURN(generic_get_impl<I, V>(
+ holds_alternative<I>(v) ? 0 : (throw_bad_variant_access(), 0))(
+ lib::forward<V>(v)))
+ } // namespace detail
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr variant_alternative_t<I, variant<Ts...>> &get(
+ variant<Ts...> &v) {
+ return detail::generic_get<I>(v);
+ }
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr variant_alternative_t<I, variant<Ts...>> &&get(
+ variant<Ts...> &&v) {
+ return detail::generic_get<I>(lib::move(v));
+ }
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr const variant_alternative_t<I, variant<Ts...>> &get(
+ const variant<Ts...> &v) {
+ return detail::generic_get<I>(v);
+ }
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr const variant_alternative_t<I, variant<Ts...>> &&get(
+ const variant<Ts...> &&v) {
+ return detail::generic_get<I>(lib::move(v));
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr T &get(variant<Ts...> &v) {
+ return get<detail::find_index_checked<T, Ts...>::value>(v);
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr T &&get(variant<Ts...> &&v) {
+ return get<detail::find_index_checked<T, Ts...>::value>(lib::move(v));
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr const T &get(const variant<Ts...> &v) {
+ return get<detail::find_index_checked<T, Ts...>::value>(v);
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr const T &&get(const variant<Ts...> &&v) {
+ return get<detail::find_index_checked<T, Ts...>::value>(lib::move(v));
+ }
+
+ namespace detail {
+
+ template <std::size_t I, typename V>
+ inline constexpr /* auto * */ AUTO generic_get_if(V *v) noexcept
+ AUTO_RETURN(v && holds_alternative<I>(*v)
+ ? lib::addressof(access::variant::get_alt<I>(*v).value)
+ : nullptr)
+
+ } // namespace detail
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr lib::add_pointer_t<variant_alternative_t<I, variant<Ts...>>>
+ get_if(variant<Ts...> *v) noexcept {
+ return detail::generic_get_if<I>(v);
+ }
+
+ template <std::size_t I, typename... Ts>
+ inline constexpr lib::add_pointer_t<
+ const variant_alternative_t<I, variant<Ts...>>>
+ get_if(const variant<Ts...> *v) noexcept {
+ return detail::generic_get_if<I>(v);
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr lib::add_pointer_t<T>
+ get_if(variant<Ts...> *v) noexcept {
+ return get_if<detail::find_index_checked<T, Ts...>::value>(v);
+ }
+
+ template <typename T, typename... Ts>
+ inline constexpr lib::add_pointer_t<const T>
+ get_if(const variant<Ts...> *v) noexcept {
+ return get_if<detail::find_index_checked<T, Ts...>::value>(v);
+ }
+
+ template <typename... Ts>
+ inline constexpr bool operator==(const variant<Ts...> &lhs,
+ const variant<Ts...> &rhs) {
+ using detail::visitation::variant;
+ using lib::equal_to;
+#ifdef MPARK_CPP14_CONSTEXPR
+ if (lhs.index() != rhs.index()) return false;
+ if (lhs.valueless_by_exception()) return true;
+ return variant::visit_value_at(lhs.index(), equal_to{}, lhs, rhs);
+#else
+ return lhs.index() == rhs.index() &&
+ (lhs.valueless_by_exception() ||
+ variant::visit_value_at(lhs.index(), equal_to{}, lhs, rhs));
+#endif
+ }
+
+ template <typename... Ts>
+ inline constexpr bool operator!=(const variant<Ts...> &lhs,
+ const variant<Ts...> &rhs) {
+ using detail::visitation::variant;
+ using lib::not_equal_to;
+#ifdef MPARK_CPP14_CONSTEXPR
+ if (lhs.index() != rhs.index()) return true;
+ if (lhs.valueless_by_exception()) return false;
+ return variant::visit_value_at(lhs.index(), not_equal_to{}, lhs, rhs);
+#else
+ return lhs.index() != rhs.index() ||
+ (!lhs.valueless_by_exception() &&
+ variant::visit_value_at(lhs.index(), not_equal_to{}, lhs, rhs));
+#endif
+ }
+
+ template <typename... Ts>
+ inline constexpr bool operator<(const variant<Ts...> &lhs,
+ const variant<Ts...> &rhs) {
+ using detail::visitation::variant;
+ using lib::less;
+#ifdef MPARK_CPP14_CONSTEXPR
+ if (rhs.valueless_by_exception()) return false;
+ if (lhs.valueless_by_exception()) return true;
+ if (lhs.index() < rhs.index()) return true;
+ if (lhs.index() > rhs.index()) return false;
+ return variant::visit_value_at(lhs.index(), less{}, lhs, rhs);
+#else
+ return !rhs.valueless_by_exception() &&
+ (lhs.valueless_by_exception() || lhs.index() < rhs.index() ||
+ (lhs.index() == rhs.index() &&
+ variant::visit_value_at(lhs.index(), less{}, lhs, rhs)));
+#endif
+ }
+
+ template <typename... Ts>
+ inline constexpr bool operator>(const variant<Ts...> &lhs,
+ const variant<Ts...> &rhs) {
+ using detail::visitation::variant;
+ using lib::greater;
+#ifdef MPARK_CPP14_CONSTEXPR
+ if (lhs.valueless_by_exception()) return false;
+ if (rhs.valueless_by_exception()) return true;
+ if (lhs.index() > rhs.index()) return true;
+ if (lhs.index() < rhs.index()) return false;
+ return variant::visit_value_at(lhs.index(), greater{}, lhs, rhs);
+#else
+ return !lhs.valueless_by_exception() &&
+ (rhs.valueless_by_exception() || lhs.index() > rhs.index() ||
+ (lhs.index() == rhs.index() &&
+ variant::visit_value_at(lhs.index(), greater{}, lhs, rhs)));
+#endif
+ }
+
+ template <typename... Ts>
+ inline constexpr bool operator<=(const variant<Ts...> &lhs,
+ const variant<Ts...> &rhs) {
+ using detail::visitation::variant;
+ using lib::less_equal;
+#ifdef MPARK_CPP14_CONSTEXPR
+ if (lhs.valueless_by_exception()) return true;
+ if (rhs.valueless_by_exception()) return false;
+ if (lhs.index() < rhs.index()) return true;
+ if (lhs.index() > rhs.index()) return false;
+ return variant::visit_value_at(lhs.index(), less_equal{}, lhs, rhs);
+#else
+ return lhs.valueless_by_exception() ||
+ (!rhs.valueless_by_exception() &&
+ (lhs.index() < rhs.index() ||
+ (lhs.index() == rhs.index() &&
+ variant::visit_value_at(lhs.index(), less_equal{}, lhs, rhs))));
+#endif
+ }
+
+ template <typename... Ts>
+ inline constexpr bool operator>=(const variant<Ts...> &lhs,
+ const variant<Ts...> &rhs) {
+ using detail::visitation::variant;
+ using lib::greater_equal;
+#ifdef MPARK_CPP14_CONSTEXPR
+ if (rhs.valueless_by_exception()) return true;
+ if (lhs.valueless_by_exception()) return false;
+ if (lhs.index() > rhs.index()) return true;
+ if (lhs.index() < rhs.index()) return false;
+ return variant::visit_value_at(lhs.index(), greater_equal{}, lhs, rhs);
+#else
+ return rhs.valueless_by_exception() ||
+ (!lhs.valueless_by_exception() &&
+ (lhs.index() > rhs.index() ||
+ (lhs.index() == rhs.index() &&
+ variant::visit_value_at(
+ lhs.index(), greater_equal{}, lhs, rhs))));
+#endif
+ }
+
+ template <typename Visitor, typename... Vs>
+ inline constexpr DECLTYPE_AUTO visit(Visitor &&visitor, Vs &&... vs)
+ DECLTYPE_AUTO_RETURN(
+ (detail::all(!vs.valueless_by_exception()...)
+ ? (void)0
+ : throw_bad_variant_access()),
+ detail::visitation::variant::visit_value(lib::forward<Visitor>(visitor),
+ lib::forward<Vs>(vs)...))
+
+ struct monostate {};
+
+ inline constexpr bool operator<(monostate, monostate) noexcept {
+ return false;
+ }
+
+ inline constexpr bool operator>(monostate, monostate) noexcept {
+ return false;
+ }
+
+ inline constexpr bool operator<=(monostate, monostate) noexcept {
+ return true;
+ }
+
+ inline constexpr bool operator>=(monostate, monostate) noexcept {
+ return true;
+ }
+
+ inline constexpr bool operator==(monostate, monostate) noexcept {
+ return true;
+ }
+
+ inline constexpr bool operator!=(monostate, monostate) noexcept {
+ return false;
+ }
+
+ template <typename... Ts>
+ inline auto swap(variant<Ts...> &lhs,
+ variant<Ts...> &rhs) noexcept(noexcept(lhs.swap(rhs)))
+ -> decltype(lhs.swap(rhs)) {
+ lhs.swap(rhs);
+ }
+
+ namespace detail {
+
+ template <typename T, typename...>
+ using enabled_type = T;
+
+ namespace hash {
+
+ template <typename H, typename K>
+ constexpr bool meets_requirements() {
+ return std::is_copy_constructible<H>::value &&
+ std::is_move_constructible<H>::value &&
+ lib::is_invocable_r<std::size_t, H, const K &>::value;
+ }
+
+ template <typename K>
+ constexpr bool is_enabled() {
+ using H = std::hash<K>;
+ return meets_requirements<H, K>() &&
+ std::is_default_constructible<H>::value &&
+ std::is_copy_assignable<H>::value &&
+ std::is_move_assignable<H>::value;
+ }
+
+ } // namespace hash
+
+ } // namespace detail
+
+#undef AUTO
+#undef AUTO_RETURN
+
+#undef AUTO_REFREF
+#undef AUTO_REFREF_RETURN
+
+#undef DECLTYPE_AUTO
+#undef DECLTYPE_AUTO_RETURN
+
+} // namespace mpark
+
+namespace std {
+
+ template <typename... Ts>
+ struct hash<mpark::detail::enabled_type<
+ mpark::variant<Ts...>,
+ mpark::lib::enable_if_t<mpark::lib::all<mpark::detail::hash::is_enabled<
+ mpark::lib::remove_const_t<Ts>>()...>::value>>> {
+ using argument_type = mpark::variant<Ts...>;
+ using result_type = std::size_t;
+
+ inline result_type operator()(const argument_type &v) const {
+ using mpark::detail::visitation::variant;
+ std::size_t result =
+ v.valueless_by_exception()
+ ? 299792458 // Random value chosen by the universe upon creation
+ : variant::visit_alt(
+#ifdef MPARK_GENERIC_LAMBDAS
+ [](const auto &alt) {
+ using alt_type = mpark::lib::decay_t<decltype(alt)>;
+ using value_type = mpark::lib::remove_const_t<
+ typename alt_type::value_type>;
+ return hash<value_type>{}(alt.value);
+ }
+#else
+ hasher{}
+#endif
+ ,
+ v);
+ return hash_combine(result, hash<std::size_t>{}(v.index()));
+ }
+
+ private:
+#ifndef MPARK_GENERIC_LAMBDAS
+ struct hasher {
+ template <typename Alt>
+ inline std::size_t operator()(const Alt &alt) const {
+ using alt_type = mpark::lib::decay_t<Alt>;
+ using value_type =
+ mpark::lib::remove_const_t<typename alt_type::value_type>;
+ return hash<value_type>{}(alt.value);
+ }
+ };
+#endif
+
+ static std::size_t hash_combine(std::size_t lhs, std::size_t rhs) {
+ return lhs ^= rhs + 0x9e3779b9 + (lhs << 6) + (lhs >> 2);
+ }
+ };
+
+ template <>
+ struct hash<mpark::monostate> {
+ using argument_type = mpark::monostate;
+ using result_type = std::size_t;
+
+ inline result_type operator()(const argument_type &) const noexcept {
+ return 66740831; // return a fundamentally attractive random value.
+ }
+ };
+
+} // namespace std
+
+#endif // MPARK_VARIANT_HPP