// <variant> -*- C++ -*-

// Copyright (C) 2016-2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file variant
 *  This is the `<variant>` C++ Library header.
 */

#ifndef _GLIBCXX_VARIANT
#define _GLIBCXX_VARIANT 1

#pragma GCC system_header

#if __cplusplus >= 201703L

#include <type_traits>
#include <utility>
#include <bits/enable_special_members.h>
#include <bits/functexcept.h>
#include <bits/move.h>
#include <bits/functional_hash.h>
#include <bits/invoke.h>
#include <ext/aligned_buffer.h>
#include <bits/parse_numbers.h>
#include <bits/stl_iterator_base_types.h>
#include <bits/stl_iterator_base_funcs.h>
#include <bits/stl_construct.h>
#if __cplusplus > 201703L
# include <compare>
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace __detail
{
namespace __variant
{
  template<size_t _Np, typename... _Types>
    struct _Nth_type;

  template<size_t _Np, typename _First, typename... _Rest>
    struct _Nth_type<_Np, _First, _Rest...>
    : _Nth_type<_Np-1, _Rest...> { };

  template<typename _First, typename... _Rest>
    struct _Nth_type<0, _First, _Rest...>
    { using type = _First; };

} // namespace __variant
} // namespace __detail

#define __cpp_lib_variant 201606L

  template<typename... _Types> class tuple;
  template<typename... _Types> class variant;
  template <typename> struct hash;

  template<typename _Variant>
    struct variant_size;

  template<typename _Variant>
    struct variant_size<const _Variant> : variant_size<_Variant> {};

  template<typename _Variant>
    struct variant_size<volatile _Variant> : variant_size<_Variant> {};

  template<typename _Variant>
    struct variant_size<const volatile _Variant> : variant_size<_Variant> {};

  template<typename... _Types>
    struct variant_size<variant<_Types...>>
    : std::integral_constant<size_t, sizeof...(_Types)> {};

  template<typename _Variant>
    inline constexpr size_t variant_size_v = variant_size<_Variant>::value;

  template<size_t _Np, typename _Variant>
    struct variant_alternative;

  template<size_t _Np, typename _First, typename... _Rest>
    struct variant_alternative<_Np, variant<_First, _Rest...>>
    : variant_alternative<_Np-1, variant<_Rest...>> {};

  template<typename _First, typename... _Rest>
    struct variant_alternative<0, variant<_First, _Rest...>>
    { using type = _First; };

  template<size_t _Np, typename _Variant>
    using variant_alternative_t =
      typename variant_alternative<_Np, _Variant>::type;

  template<size_t _Np, typename _Variant>
    struct variant_alternative<_Np, const _Variant>
    { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; };

  template<size_t _Np, typename _Variant>
    struct variant_alternative<_Np, volatile _Variant>
    { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; };

  template<size_t _Np, typename _Variant>
    struct variant_alternative<_Np, const volatile _Variant>
    { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; };

  inline constexpr size_t variant_npos = -1;

  template<size_t _Np, typename... _Types>
    constexpr variant_alternative_t<_Np, variant<_Types...>>&
    get(variant<_Types...>&);

  template<size_t _Np, typename... _Types>
    constexpr variant_alternative_t<_Np, variant<_Types...>>&&
    get(variant<_Types...>&&);

  template<size_t _Np, typename... _Types>
    constexpr variant_alternative_t<_Np, variant<_Types...>> const&
    get(const variant<_Types...>&);

  template<size_t _Np, typename... _Types>
    constexpr variant_alternative_t<_Np, variant<_Types...>> const&&
    get(const variant<_Types...>&&);

  template<typename _Result_type, typename _Visitor, typename... _Variants>
    constexpr decltype(auto)
    __do_visit(_Visitor&& __visitor, _Variants&&... __variants);

  template <typename... _Types, typename _Tp>
    decltype(auto)
    __variant_cast(_Tp&& __rhs)
    {
      if constexpr (is_lvalue_reference_v<_Tp>)
	{
	  if constexpr (is_const_v<remove_reference_t<_Tp>>)
	    return static_cast<const variant<_Types...>&>(__rhs);
	  else
	    return static_cast<variant<_Types...>&>(__rhs);
	}
      else
        return static_cast<variant<_Types...>&&>(__rhs);
    }

namespace __detail
{
namespace __variant
{
  // Returns the first appearence of _Tp in _Types.
  // Returns sizeof...(_Types) if _Tp is not in _Types.
  template<typename _Tp, typename... _Types>
    struct __index_of : std::integral_constant<size_t, 0> {};

  template<typename _Tp, typename... _Types>
    inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;

  template<typename _Tp, typename _First, typename... _Rest>
    struct __index_of<_Tp, _First, _Rest...> :
      std::integral_constant<size_t, is_same_v<_Tp, _First>
	? 0 : __index_of_v<_Tp, _Rest...> + 1> {};

  // used for raw visitation
  struct __variant_cookie {};
  // used for raw visitation with indices passed in
  struct __variant_idx_cookie { using type = __variant_idx_cookie; };
  // Used to enable deduction (and same-type checking) for std::visit:
  template<typename> struct __deduce_visit_result { };

  // Visit variants that might be valueless.
  template<typename _Visitor, typename... _Variants>
    constexpr void
    __raw_visit(_Visitor&& __visitor, _Variants&&... __variants)
    {
      std::__do_visit<__variant_cookie>(std::forward<_Visitor>(__visitor),
				        std::forward<_Variants>(__variants)...);
    }

  // Visit variants that might be valueless, passing indices to the visitor.
  template<typename _Visitor, typename... _Variants>
    constexpr void
    __raw_idx_visit(_Visitor&& __visitor, _Variants&&... __variants)
    {
      std::__do_visit<__variant_idx_cookie>(std::forward<_Visitor>(__visitor),
	  std::forward<_Variants>(__variants)...);
    }

  // _Uninitialized<T> is guaranteed to be a trivially destructible type,
  // even if T is not.
  template<typename _Type, bool = std::is_trivially_destructible_v<_Type>>
    struct _Uninitialized;

  template<typename _Type>
    struct _Uninitialized<_Type, true>
    {
      template<typename... _Args>
	constexpr
	_Uninitialized(in_place_index_t<0>, _Args&&... __args)
	: _M_storage(std::forward<_Args>(__args)...)
	{ }

      constexpr const _Type& _M_get() const & noexcept
      { return _M_storage; }

      constexpr _Type& _M_get() & noexcept
      { return _M_storage; }

      constexpr const _Type&& _M_get() const && noexcept
      { return std::move(_M_storage); }

      constexpr _Type&& _M_get() && noexcept
      { return std::move(_M_storage); }

      _Type _M_storage;
    };

  template<typename _Type>
    struct _Uninitialized<_Type, false>
    {
      template<typename... _Args>
	constexpr
	_Uninitialized(in_place_index_t<0>, _Args&&... __args)
	{
	  ::new ((void*)std::addressof(_M_storage))
	    _Type(std::forward<_Args>(__args)...);
	}

      const _Type& _M_get() const & noexcept
      { return *_M_storage._M_ptr(); }

      _Type& _M_get() & noexcept
      { return *_M_storage._M_ptr(); }

      const _Type&& _M_get() const && noexcept
      { return std::move(*_M_storage._M_ptr()); }

      _Type&& _M_get() && noexcept
      { return std::move(*_M_storage._M_ptr()); }

      __gnu_cxx::__aligned_membuf<_Type> _M_storage;
    };

  template<typename _Union>
    constexpr decltype(auto)
    __get(in_place_index_t<0>, _Union&& __u) noexcept
    { return std::forward<_Union>(__u)._M_first._M_get(); }

  template<size_t _Np, typename _Union>
    constexpr decltype(auto)
    __get(in_place_index_t<_Np>, _Union&& __u) noexcept
    {
      return __variant::__get(in_place_index<_Np-1>,
			      std::forward<_Union>(__u)._M_rest);
    }

  // Returns the typed storage for __v.
  template<size_t _Np, typename _Variant>
    constexpr decltype(auto)
    __get(_Variant&& __v) noexcept
    {
      return __variant::__get(std::in_place_index<_Np>,
			      std::forward<_Variant>(__v)._M_u);
    }

  template<typename... _Types>
    struct _Traits
    {
      static constexpr bool _S_default_ctor =
	  is_default_constructible_v<typename _Nth_type<0, _Types...>::type>;
      static constexpr bool _S_copy_ctor =
	  (is_copy_constructible_v<_Types> && ...);
      static constexpr bool _S_move_ctor =
	  (is_move_constructible_v<_Types> && ...);
      static constexpr bool _S_copy_assign =
	  _S_copy_ctor
	  && (is_copy_assignable_v<_Types> && ...);
      static constexpr bool _S_move_assign =
	  _S_move_ctor
	  && (is_move_assignable_v<_Types> && ...);

      static constexpr bool _S_trivial_dtor =
	  (is_trivially_destructible_v<_Types> && ...);
      static constexpr bool _S_trivial_copy_ctor =
	  (is_trivially_copy_constructible_v<_Types> && ...);
      static constexpr bool _S_trivial_move_ctor =
	  (is_trivially_move_constructible_v<_Types> && ...);
      static constexpr bool _S_trivial_copy_assign =
	  _S_trivial_dtor && _S_trivial_copy_ctor
	  && (is_trivially_copy_assignable_v<_Types> && ...);
      static constexpr bool _S_trivial_move_assign =
	  _S_trivial_dtor && _S_trivial_move_ctor
	  && (is_trivially_move_assignable_v<_Types> && ...);

      // The following nothrow traits are for non-trivial SMFs. Trivial SMFs
      // are always nothrow.
      static constexpr bool _S_nothrow_default_ctor =
	  is_nothrow_default_constructible_v<
	      typename _Nth_type<0, _Types...>::type>;
      static constexpr bool _S_nothrow_copy_ctor = false;
      static constexpr bool _S_nothrow_move_ctor =
	  (is_nothrow_move_constructible_v<_Types> && ...);
      static constexpr bool _S_nothrow_copy_assign = false;
      static constexpr bool _S_nothrow_move_assign =
	  _S_nothrow_move_ctor
	  && (is_nothrow_move_assignable_v<_Types> && ...);
    };

  // Defines members and ctors.
  template<typename... _Types>
    union _Variadic_union { };

  template<typename _First, typename... _Rest>
    union _Variadic_union<_First, _Rest...>
    {
      constexpr _Variadic_union() : _M_rest() { }

      template<typename... _Args>
	constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args)
	: _M_first(in_place_index<0>, std::forward<_Args>(__args)...)
	{ }

      template<size_t _Np, typename... _Args>
	constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args)
	: _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...)
	{ }

      _Uninitialized<_First> _M_first;
      _Variadic_union<_Rest...> _M_rest;
    };

  // _Never_valueless_alt is true for variant alternatives that can
  // always be placed in a variant without it becoming valueless.

  // For suitably-small, trivially copyable types we can create temporaries
  // on the stack and then memcpy them into place.
  template<typename _Tp>
    struct _Never_valueless_alt
    : __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>>
    { };

  // Specialize _Never_valueless_alt for other types which have a
  // non-throwing and cheap move construction and move assignment operator,
  // so that emplacing the type will provide the strong exception-safety
  // guarantee, by creating and moving a temporary.
  // Whether _Never_valueless_alt<T> is true or not affects the ABI of a
  // variant using that alternative, so we can't change the value later!

  // True if every alternative in _Types... can be emplaced in a variant
  // without it becoming valueless. If this is true, variant<_Types...>
  // can never be valueless, which enables some minor optimizations.
  template <typename... _Types>
    constexpr bool __never_valueless()
    {
      return _Traits<_Types...>::_S_move_assign
	&& (_Never_valueless_alt<_Types>::value && ...);
    }

  // Defines index and the dtor, possibly trivial.
  template<bool __trivially_destructible, typename... _Types>
    struct _Variant_storage;

  template <typename... _Types>
    using __select_index =
      typename __select_int::_Select_int_base<sizeof...(_Types),
					      unsigned char,
					      unsigned short>::type::value_type;

  template<typename... _Types>
    struct _Variant_storage<false, _Types...>
    {
      constexpr
      _Variant_storage()
      : _M_index(static_cast<__index_type>(variant_npos))
      { }

      template<size_t _Np, typename... _Args>
	constexpr
	_Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
	: _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
	_M_index{_Np}
	{ }

      void _M_reset()
      {
	if (!_M_valid()) [[unlikely]]
	  return;

	std::__do_visit<void>([](auto&& __this_mem) mutable
	  {
	    std::_Destroy(std::__addressof(__this_mem));
	  }, __variant_cast<_Types...>(*this));

	_M_index = static_cast<__index_type>(variant_npos);
      }

      ~_Variant_storage()
      { _M_reset(); }

      void*
      _M_storage() const noexcept
      {
	return const_cast<void*>(static_cast<const void*>(
	    std::addressof(_M_u)));
      }

      constexpr bool
      _M_valid() const noexcept
      {
	if constexpr (__variant::__never_valueless<_Types...>())
	  return true;
	return this->_M_index != __index_type(variant_npos);
      }

      _Variadic_union<_Types...> _M_u;
      using __index_type = __select_index<_Types...>;
      __index_type _M_index;
    };

  template<typename... _Types>
    struct _Variant_storage<true, _Types...>
    {
      constexpr
      _Variant_storage()
      : _M_index(static_cast<__index_type>(variant_npos))
      { }

      template<size_t _Np, typename... _Args>
	constexpr
	_Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
	: _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
	_M_index{_Np}
	{ }

      void _M_reset() noexcept
      { _M_index = static_cast<__index_type>(variant_npos); }

      void*
      _M_storage() const noexcept
      {
	return const_cast<void*>(static_cast<const void*>(
	    std::addressof(_M_u)));
      }

      constexpr bool
      _M_valid() const noexcept
      {
	if constexpr (__variant::__never_valueless<_Types...>())
	  return true;
	return this->_M_index != static_cast<__index_type>(variant_npos);
      }

      _Variadic_union<_Types...> _M_u;
      using __index_type = __select_index<_Types...>;
      __index_type _M_index;
    };

  template<typename... _Types>
    using _Variant_storage_alias =
	_Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>;

  template<typename _Tp, typename _Up>
    void __variant_construct_single(_Tp&& __lhs, _Up&& __rhs_mem)
    {
      void* __storage = std::addressof(__lhs._M_u);
      using _Type = remove_reference_t<decltype(__rhs_mem)>;
      if constexpr (!is_same_v<_Type, __variant_cookie>)
        ::new (__storage)
	  _Type(std::forward<decltype(__rhs_mem)>(__rhs_mem));
    }

  template<typename... _Types, typename _Tp, typename _Up>
    void __variant_construct(_Tp&& __lhs, _Up&& __rhs)
    {
      __lhs._M_index = __rhs._M_index;
      __variant::__raw_visit([&__lhs](auto&& __rhs_mem) mutable
        {
	  __variant_construct_single(std::forw                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            