include/experimental/propagate_const - llvm-project/libcxx - Git at Google

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #ifndef _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST
 #define _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST

 /*
     propagate_const synopsis

     namespace std { namespace experimental { inline namespace fundamentals_v2 {

     // [propagate_const]
     template <class T> class propagate_const;

     // [propagate_const.underlying], underlying pointer access
     constexpr const _Tp& get_underlying(const propagate_const<T>& pt) noexcept;
     constexpr T& get_underlying(propagate_const<T>& pt) noexcept;

     // [propagate_const.relational], relational operators
     template <class T> constexpr bool operator==(const propagate_const<T>& pt, nullptr_t);
     template <class T> constexpr bool operator==(nullptr_t, const propagate_const<T>& pu);
     template <class T> constexpr bool operator!=(const propagate_const<T>& pt, nullptr_t);
     template <class T> constexpr bool operator!=(nullptr_t, const propagate_const<T>& pu);
     template <class T, class U> constexpr bool operator==(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator!=(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator<(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator>(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator<=(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator>=(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator==(const propagate_const<T>& pt, const _Up& u);
     template <class T, class U> constexpr bool operator!=(const propagate_const<T>& pt, const _Up& u);
     template <class T, class U> constexpr bool operator<(const propagate_const<T>& pt, const _Up& u);
     template <class T, class U> constexpr bool operator>(const propagate_const<T>& pt, const _Up& u);
     template <class T, class U> constexpr bool operator<=(const propagate_const<T>& pt, const _Up& u);
     template <class T, class U> constexpr bool operator>=(const propagate_const<T>& pt, const _Up& u);
     template <class T, class U> constexpr bool operator==(const _Tp& t, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator!=(const _Tp& t, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator<(const _Tp& t, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator>(const _Tp& t, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator<=(const _Tp& t, const propagate_const<_Up>& pu);
     template <class T, class U> constexpr bool operator>=(const _Tp& t, const propagate_const<_Up>& pu);

     // [propagate_const.algorithms], specialized algorithms
     template <class T> constexpr void swap(propagate_const<T>& pt, propagate_const<T>& pu) noexcept(see below);

     template <class T>
     class propagate_const
     {

     public:
       typedef remove_reference_t<decltype(*declval<T&>())> element_type;

       // [propagate_const.ctor], constructors
       constexpr propagate_const() = default;
       propagate_const(const propagate_const& p) = delete;
       constexpr propagate_const(propagate_const&& p) = default;
       template <class U> EXPLICIT constexpr propagate_const(propagate_const<_Up>&& pu); // see below
       template <class U> EXPLICIT constexpr propagate_const(U&& u); // see below

       // [propagate_const.assignment], assignment
       propagate_const& operator=(const propagate_const& p) = delete;
       constexpr propagate_const& operator=(propagate_const&& p) = default;
       template <class U> constexpr propagate_const& operator=(propagate_const<_Up>&& pu);
       template <class U> constexpr propagate_const& operator=(U&& u); // see below

       // [propagate_const.const_observers], const observers
       explicit constexpr operator bool() const;
       constexpr const element_type* operator->() const;
       constexpr operator const element_type*() const; // Not always defined
       constexpr const element_type& operator*() const;
       constexpr const element_type* get() const;

       // [propagate_const.non_const_observers], non-const observers
       constexpr element_type* operator->();
       constexpr operator element_type*(); // Not always defined
       constexpr element_type& operator*();
       constexpr element_type* get();

       // [propagate_const.modifiers], modifiers
       constexpr void swap(propagate_const& pt) noexcept(see below)

     private:
       T t_; // exposition only
     };

   } // namespace fundamentals_v2
   } // namespace experimental

   // [propagate_const.hash], hash support
   template <class T> struct hash<experimental::propagate_const<T>>;

   // [propagate_const.comparison_function_objects], comparison function objects
   template <class T> struct equal_to<experimental::propagate_const<T>>;
   template <class T> struct not_equal_to<experimental::propagate_const<T>>;
   template <class T> struct less<experimental::propagate_const<T>>;
   template <class T> struct greater<experimental::propagate_const<T>>;
   template <class T> struct less_equal<experimental::propagate_const<T>>;
   template <class T> struct greater_equal<experimental::propagate_const<T>>;

 } // namespace std

 */

 #include <__functional/operations.h>
 #include <__fwd/functional.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/decay.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_array.h>
 #include <__type_traits/is_constructible.h>
 #include <__type_traits/is_convertible.h>
 #include <__type_traits/is_function.h>
 #include <__type_traits/is_pointer.h>
 #include <__type_traits/is_reference.h>
 #include <__type_traits/is_same.h>
 #include <__type_traits/is_swappable.h>
 #include <__type_traits/remove_cv.h>
 #include <__type_traits/remove_pointer.h>
 #include <__type_traits/remove_reference.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <cstddef>
 #include <experimental/__config>

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif

 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>

 #if _LIBCPP_STD_VER >= 14

 _LIBCPP_BEGIN_NAMESPACE_LFTS_V2

 template <class _Tp>
 class propagate_const;

 template <class _Up>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const _Up& get_underlying(const propagate_const<_Up>& __pu) _NOEXCEPT;

 template <class _Up>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Up& get_underlying(propagate_const<_Up>& __pu) _NOEXCEPT;

 template <class _Tp>
 class propagate_const {
 public:
   typedef remove_reference_t<decltype(*std::declval<_Tp&>())> element_type;

   static_assert(!is_array<_Tp>::value, "Instantiation of propagate_const with an array type is ill-formed.");
   static_assert(!is_reference<_Tp>::value, "Instantiation of propagate_const with a reference type is ill-formed.");
   static_assert(!(is_pointer<_Tp>::value && is_function<__remove_pointer_t<_Tp> >::value),
                 "Instantiation of propagate_const with a function-pointer type is ill-formed.");
   static_assert(!(is_pointer<_Tp>::value && is_same<__remove_cv_t<__remove_pointer_t<_Tp> >, void>::value),
                 "Instantiation of propagate_const with a pointer to (possibly cv-qualified) void is ill-formed.");

 private:
   template <class _Up>
   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* __get_pointer(_Up* __u) {
     return __u;
   }

   template <class _Up>
   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* __get_pointer(_Up& __u) {
     return __get_pointer(__u.get());
   }

   template <class _Up>
   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* __get_pointer(const _Up* __u) {
     return __u;
   }

   template <class _Up>
   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* __get_pointer(const _Up& __u) {
     return __get_pointer(__u.get());
   }

   template <class _Up>
   struct __is_propagate_const : false_type {};

   template <class _Up>
   struct __is_propagate_const<propagate_const<_Up>> : true_type {};

   _Tp __t_;

 public:
   template <class _Up>
   friend _LIBCPP_CONSTEXPR const _Up&
   experimental::fundamentals_v2::get_underlying(const propagate_const<_Up>& __pu) _NOEXCEPT;
   template <class _Up>
   friend _LIBCPP_CONSTEXPR _Up& experimental::fundamentals_v2::get_underlying(propagate_const<_Up>& __pu) _NOEXCEPT;

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const() = default;

   propagate_const(const propagate_const&) = delete;

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(propagate_const&&) = default;

   template <class _Up,
             enable_if_t<!is_convertible<_Up, _Tp>::value && is_constructible<_Tp, _Up&&>::value, bool> = true>
   explicit _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(propagate_const<_Up>&& __pu)
       : __t_(std::move(experimental::get_underlying(__pu))) {}

   template <class _Up,
             enable_if_t<is_convertible<_Up&&, _Tp>::value && is_constructible<_Tp, _Up&&>::value, bool> = false>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(propagate_const<_Up>&& __pu)
       : __t_(std::move(experimental::get_underlying(__pu))) {}

   template <class _Up,
             enable_if_t<!is_convertible<_Up&&, _Tp>::value && is_constructible<_Tp, _Up&&>::value &&
                             !__is_propagate_const<decay_t<_Up>>::value,
                         bool> = true>
   explicit _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(_Up&& __u) : __t_(std::forward<_Up>(__u)) {}

   template <class _Up,
             enable_if_t<is_convertible<_Up&&, _Tp>::value && is_constructible<_Tp, _Up&&>::value &&
                             !__is_propagate_const<decay_t<_Up>>::value,
                         bool> = false>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(_Up&& __u) : __t_(std::forward<_Up>(__u)) {}

   propagate_const& operator=(const propagate_const&) = delete;

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const& operator=(propagate_const&&) = default;

   template <class _Up>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const& operator=(propagate_const<_Up>&& __pu) {
     __t_ = std::move(experimental::get_underlying(__pu));
     return *this;
   }

   template <class _Up, class _Vp = enable_if_t<!__is_propagate_const<decay_t<_Up>>::value>>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const& operator=(_Up&& __u) {
     __t_ = std::forward<_Up>(__u);
     return *this;
   }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* get() const { return __get_pointer(__t_); }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* get() { return __get_pointer(__t_); }

   _LIBCPP_HIDE_FROM_ABI explicit _LIBCPP_CONSTEXPR operator bool() const { return get() != nullptr; }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* operator->() const { return get(); }

   template <class _Dummy = _Tp, class _Up = enable_if_t<is_convertible< const _Dummy, const element_type*>::value>>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR operator const element_type*() const {
     return get();
   }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type& operator*() const { return *get(); }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* operator->() { return get(); }

   template <class _Dummy = _Tp, class _Up = enable_if_t< is_convertible<_Dummy, element_type*>::value>>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR operator element_type*() {
     return get();
   }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type& operator*() { return *get(); }

   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void swap(propagate_const& __pt)
       _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value) {
     using std::swap;
     swap(__t_, __pt.__t_);
   }
 };

 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(const propagate_const<_Tp>& __pt, nullptr_t) {
   return experimental::get_underlying(__pt) == nullptr;
 }

 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(nullptr_t, const propagate_const<_Tp>& __pt) {
   return nullptr == experimental::get_underlying(__pt);
 }

 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(const propagate_const<_Tp>& __pt, nullptr_t) {
   return experimental::get_underlying(__pt) != nullptr;
 }

 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(nullptr_t, const propagate_const<_Tp>& __pt) {
   return nullptr != experimental::get_underlying(__pt);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator==(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
   return experimental::get_underlying(__pt) == experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator!=(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
   return experimental::get_underlying(__pt) != experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator<(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
   return experimental::get_underlying(__pt) < experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator>(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
   return experimental::get_underlying(__pt) > experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator<=(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
   return experimental::get_underlying(__pt) <= experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
 operator>=(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
   return experimental::get_underlying(__pt) >= experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(const propagate_const<_Tp>& __pt, const _Up& __u) {
   return experimental::get_underlying(__pt) == __u;
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(const propagate_const<_Tp>& __pt, const _Up& __u) {
   return experimental::get_underlying(__pt) != __u;
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<(const propagate_const<_Tp>& __pt, const _Up& __u) {
   return experimental::get_underlying(__pt) < __u;
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>(const propagate_const<_Tp>& __pt, const _Up& __u) {
   return experimental::get_underlying(__pt) > __u;
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<=(const propagate_const<_Tp>& __pt, const _Up& __u) {
   return experimental::get_underlying(__pt) <= __u;
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>=(const propagate_const<_Tp>& __pt, const _Up& __u) {
   return experimental::get_underlying(__pt) >= __u;
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(const _Tp& __t, const propagate_const<_Up>& __pu) {
   return __t == experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(const _Tp& __t, const propagate_const<_Up>& __pu) {
   return __t != experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<(const _Tp& __t, const propagate_const<_Up>& __pu) {
   return __t < experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>(const _Tp& __t, const propagate_const<_Up>& __pu) {
   return __t > experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<=(const _Tp& __t, const propagate_const<_Up>& __pu) {
   return __t <= experimental::get_underlying(__pu);
 }

 template <class _Tp, class _Up>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>=(const _Tp& __t, const propagate_const<_Up>& __pu) {
   return __t >= experimental::get_underlying(__pu);
 }

 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void swap(propagate_const<_Tp>& __pc1, propagate_const<_Tp>& __pc2)
     _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value) {
   __pc1.swap(__pc2);
 }

 template <class _Tp>
 _LIBCPP_CONSTEXPR const _Tp& get_underlying(const propagate_const<_Tp>& __pt) _NOEXCEPT {
   return __pt.__t_;
 }

 template <class _Tp>
 _LIBCPP_CONSTEXPR _Tp& get_underlying(propagate_const<_Tp>& __pt) _NOEXCEPT {
   return __pt.__t_;
 }

 _LIBCPP_END_NAMESPACE_LFTS_V2

 _LIBCPP_BEGIN_NAMESPACE_STD

 template <class _Tp>
 struct hash<experimental::propagate_const<_Tp>> {
   typedef size_t result_type;
   typedef experimental::propagate_const<_Tp> argument_type;

   _LIBCPP_HIDE_FROM_ABI size_t operator()(const experimental::propagate_const<_Tp>& __pc1) const {
     return std::hash<_Tp>()(experimental::get_underlying(__pc1));
   }
 };

 template <class _Tp>
 struct equal_to<experimental::propagate_const<_Tp>> {
   typedef experimental::propagate_const<_Tp> first_argument_type;
   typedef experimental::propagate_const<_Tp> second_argument_type;

   _LIBCPP_HIDE_FROM_ABI bool
   operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
     return std::equal_to<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
   }
 };

 template <class _Tp>
 struct not_equal_to<experimental::propagate_const<_Tp>> {
   typedef experimental::propagate_const<_Tp> first_argument_type;
   typedef experimental::propagate_const<_Tp> second_argument_type;

   _LIBCPP_HIDE_FROM_ABI bool
   operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
     return std::not_equal_to<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
   }
 };

 template <class _Tp>
 struct less<experimental::propagate_const<_Tp>> {
   typedef experimental::propagate_const<_Tp> first_argument_type;
   typedef experimental::propagate_const<_Tp> second_argument_type;

   _LIBCPP_HIDE_FROM_ABI bool
   operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
     return std::less<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
   }
 };

 template <class _Tp>
 struct greater<experimental::propagate_const<_Tp>> {
   typedef experimental::propagate_const<_Tp> first_argument_type;
   typedef experimental::propagate_const<_Tp> second_argument_type;

   _LIBCPP_HIDE_FROM_ABI bool
   operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
     return std::greater<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
   }
 };

 template <class _Tp>
 struct less_equal<experimental::propagate_const<_Tp>> {
   typedef experimental::propagate_const<_Tp> first_argument_type;
   typedef experimental::propagate_const<_Tp> second_argument_type;

   _LIBCPP_HIDE_FROM_ABI bool
   operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
     return std::less_equal<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
   }
 };

 template <class _Tp>
 struct greater_equal<experimental::propagate_const<_Tp>> {
   typedef experimental::propagate_const<_Tp> first_argument_type;
   typedef experimental::propagate_const<_Tp> second_argument_type;

   _LIBCPP_HIDE_FROM_ABI bool
   operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
     return std::greater_equal<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
   }
 };

 _LIBCPP_END_NAMESPACE_STD

 #endif // _LIBCPP_STD_VER >= 14

 _LIBCPP_POP_MACROS

 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <type_traits>
 #endif

 #endif // _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST
	// -- C++ --
	//===----------------------------------------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#ifndef _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST
	#define _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST

	/*
	propagate_const synopsis

	namespace std { namespace experimental { inline namespace fundamentals_v2 {

	// [propagate_const]
	template <class T> class propagate_const;

	// [propagate_const.underlying], underlying pointer access
	constexpr const _Tp& get_underlying(const propagate_const<T>& pt) noexcept;
	constexpr T& get_underlying(propagate_const<T>& pt) noexcept;

	// [propagate_const.relational], relational operators
	template <class T> constexpr bool operator==(const propagate_const<T>& pt, nullptr_t);
	template <class T> constexpr bool operator==(nullptr_t, const propagate_const<T>& pu);
	template <class T> constexpr bool operator!=(const propagate_const<T>& pt, nullptr_t);
	template <class T> constexpr bool operator!=(nullptr_t, const propagate_const<T>& pu);
	template <class T, class U> constexpr bool operator==(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator!=(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator<(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator>(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator<=(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator>=(const propagate_const<T>& pt, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator==(const propagate_const<T>& pt, const _Up& u);
	template <class T, class U> constexpr bool operator!=(const propagate_const<T>& pt, const _Up& u);
	template <class T, class U> constexpr bool operator<(const propagate_const<T>& pt, const _Up& u);
	template <class T, class U> constexpr bool operator>(const propagate_const<T>& pt, const _Up& u);
	template <class T, class U> constexpr bool operator<=(const propagate_const<T>& pt, const _Up& u);
	template <class T, class U> constexpr bool operator>=(const propagate_const<T>& pt, const _Up& u);
	template <class T, class U> constexpr bool operator==(const _Tp& t, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator!=(const _Tp& t, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator<(const _Tp& t, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator>(const _Tp& t, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator<=(const _Tp& t, const propagate_const<_Up>& pu);
	template <class T, class U> constexpr bool operator>=(const _Tp& t, const propagate_const<_Up>& pu);

	// [propagate_const.algorithms], specialized algorithms
	template <class T> constexpr void swap(propagate_const<T>& pt, propagate_const<T>& pu) noexcept(see below);

	template <class T>
	class propagate_const
	{

	public:
	typedef remove_reference_t<decltype(*declval<T&>())> element_type;

	// [propagate_const.ctor], constructors
	constexpr propagate_const() = default;
	propagate_const(const propagate_const& p) = delete;
	constexpr propagate_const(propagate_const&& p) = default;
	template <class U> EXPLICIT constexpr propagate_const(propagate_const<_Up>&& pu); // see below
	template <class U> EXPLICIT constexpr propagate_const(U&& u); // see below

	// [propagate_const.assignment], assignment
	propagate_const& operator=(const propagate_const& p) = delete;
	constexpr propagate_const& operator=(propagate_const&& p) = default;
	template <class U> constexpr propagate_const& operator=(propagate_const<_Up>&& pu);
	template <class U> constexpr propagate_const& operator=(U&& u); // see below

	// [propagate_const.const_observers], const observers
	explicit constexpr operator bool() const;
	constexpr const element_type* operator->() const;
	constexpr operator const element_type*() const; // Not always defined
	constexpr const element_type& operator*() const;
	constexpr const element_type* get() const;

	// [propagate_const.non_const_observers], non-const observers
	constexpr element_type* operator->();
	constexpr operator element_type*(); // Not always defined
	constexpr element_type& operator*();
	constexpr element_type* get();

	// [propagate_const.modifiers], modifiers
	constexpr void swap(propagate_const& pt) noexcept(see below)

	private:
	T t_; // exposition only
	};

	} // namespace fundamentals_v2
	} // namespace experimental

	// [propagate_const.hash], hash support
	template <class T> struct hash<experimental::propagate_const<T>>;

	// [propagate_const.comparison_function_objects], comparison function objects
	template <class T> struct equal_to<experimental::propagate_const<T>>;
	template <class T> struct not_equal_to<experimental::propagate_const<T>>;
	template <class T> struct less<experimental::propagate_const<T>>;
	template <class T> struct greater<experimental::propagate_const<T>>;
	template <class T> struct less_equal<experimental::propagate_const<T>>;
	template <class T> struct greater_equal<experimental::propagate_const<T>>;

	} // namespace std

	*/

	#include <__functional/operations.h>
	#include <__fwd/functional.h>
	#include <__type_traits/conditional.h>
	#include <__type_traits/decay.h>
	#include <__type_traits/enable_if.h>
	#include <__type_traits/is_array.h>
	#include <__type_traits/is_constructible.h>
	#include <__type_traits/is_convertible.h>
	#include <__type_traits/is_function.h>
	#include <__type_traits/is_pointer.h>
	#include <__type_traits/is_reference.h>
	#include <__type_traits/is_same.h>
	#include <__type_traits/is_swappable.h>
	#include <__type_traits/remove_cv.h>
	#include <__type_traits/remove_pointer.h>
	#include <__type_traits/remove_reference.h>
	#include <__utility/declval.h>
	#include <__utility/forward.h>
	#include <__utility/move.h>
	#include <__utility/swap.h>
	#include <cstddef>
	#include <experimental/__config>

	#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
	# pragma GCC system_header
	#endif

	_LIBCPP_PUSH_MACROS
	#include <__undef_macros>

	#if _LIBCPP_STD_VER >= 14

	_LIBCPP_BEGIN_NAMESPACE_LFTS_V2

	template <class _Tp>
	class propagate_const;

	template <class _Up>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const _Up& get_underlying(const propagate_const<_Up>& __pu) _NOEXCEPT;

	template <class _Up>
	inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Up& get_underlying(propagate_const<_Up>& __pu) _NOEXCEPT;

	template <class _Tp>
	class propagate_const {
	public:
	typedef remove_reference_t<decltype(*std::declval<_Tp&>())> element_type;

	static_assert(!is_array<_Tp>::value, "Instantiation of propagate_const with an array type is ill-formed.");
	static_assert(!is_reference<_Tp>::value, "Instantiation of propagate_const with a reference type is ill-formed.");
	static_assert(!(is_pointer<_Tp>::value && is_function<__remove_pointer_t<_Tp> >::value),
	"Instantiation of propagate_const with a function-pointer type is ill-formed.");
	static_assert(!(is_pointer<_Tp>::value && is_same<__remove_cv_t<__remove_pointer_t<_Tp> >, void>::value),
	"Instantiation of propagate_const with a pointer to (possibly cv-qualified) void is ill-formed.");

	private:
	template <class _Up>
	static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* __get_pointer(_Up* __u) {
	return __u;
	}

	template <class _Up>
	static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* __get_pointer(_Up& __u) {
	return __get_pointer(__u.get());
	}

	template <class _Up>
	static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* __get_pointer(const _Up* __u) {
	return __u;
	}

	template <class _Up>
	static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* __get_pointer(const _Up& __u) {
	return __get_pointer(__u.get());
	}

	template <class _Up>
	struct __is_propagate_const : false_type {};

	template <class _Up>
	struct __is_propagate_const<propagate_const<_Up>> : true_type {};

	_Tp __t_;

	public:
	template <class _Up>
	friend _LIBCPP_CONSTEXPR const _Up&
	experimental::fundamentals_v2::get_underlying(const propagate_const<_Up>& __pu) _NOEXCEPT;
	template <class _Up>
	friend _LIBCPP_CONSTEXPR _Up& experimental::fundamentals_v2::get_underlying(propagate_const<_Up>& __pu) _NOEXCEPT;

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const() = default;

	propagate_const(const propagate_const&) = delete;

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(propagate_const&&) = default;

	template <class _Up,
	enable_if_t<!is_convertible<_Up, _Tp>::value && is_constructible<_Tp, _Up&&>::value, bool> = true>
	explicit _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(propagate_const<_Up>&& __pu)
	: __t_(std::move(experimental::get_underlying(__pu))) {}

	template <class _Up,
	enable_if_t<is_convertible<_Up&&, _Tp>::value && is_constructible<_Tp, _Up&&>::value, bool> = false>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(propagate_const<_Up>&& __pu)
	: __t_(std::move(experimental::get_underlying(__pu))) {}

	template <class _Up,
	enable_if_t<!is_convertible<_Up&&, _Tp>::value && is_constructible<_Tp, _Up&&>::value &&
	!__is_propagate_const<decay_t<_Up>>::value,
	bool> = true>
	explicit _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(_Up&& __u) : __t_(std::forward<_Up>(__u)) {}

	template <class _Up,
	enable_if_t<is_convertible<_Up&&, _Tp>::value && is_constructible<_Tp, _Up&&>::value &&
	!__is_propagate_const<decay_t<_Up>>::value,
	bool> = false>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const(_Up&& __u) : __t_(std::forward<_Up>(__u)) {}

	propagate_const& operator=(const propagate_const&) = delete;

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const& operator=(propagate_const&&) = default;

	template <class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const& operator=(propagate_const<_Up>&& __pu) {
	__t_ = std::move(experimental::get_underlying(__pu));
	return *this;
	}

	template <class _Up, class _Vp = enable_if_t<!__is_propagate_const<decay_t<_Up>>::value>>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR propagate_const& operator=(_Up&& __u) {
	__t_ = std::forward<_Up>(__u);
	return *this;
	}

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* get() const { return __get_pointer(__t_); }

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* get() { return __get_pointer(__t_); }

	_LIBCPP_HIDE_FROM_ABI explicit _LIBCPP_CONSTEXPR operator bool() const { return get() != nullptr; }

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type* operator->() const { return get(); }

	template <class _Dummy = _Tp, class _Up = enable_if_t<is_convertible< const _Dummy, const element_type*>::value>>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR operator const element_type*() const {
	return get();
	}

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const element_type& operator() const { return get(); }

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type* operator->() { return get(); }

	template <class _Dummy = _Tp, class _Up = enable_if_t< is_convertible<_Dummy, element_type*>::value>>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR operator element_type*() {
	return get();
	}

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR element_type& operator() { return get(); }

	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void swap(propagate_const& __pt)
	_NOEXCEPT_(__is_nothrow_swappable<_Tp>::value) {
	using std::swap;
	swap(__t_, __pt.__t_);
	}
	};

	template <class _Tp>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(const propagate_const<_Tp>& __pt, nullptr_t) {
	return experimental::get_underlying(__pt) == nullptr;
	}

	template <class _Tp>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(nullptr_t, const propagate_const<_Tp>& __pt) {
	return nullptr == experimental::get_underlying(__pt);
	}

	template <class _Tp>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(const propagate_const<_Tp>& __pt, nullptr_t) {
	return experimental::get_underlying(__pt) != nullptr;
	}

	template <class _Tp>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(nullptr_t, const propagate_const<_Tp>& __pt) {
	return nullptr != experimental::get_underlying(__pt);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
	operator==(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
	return experimental::get_underlying(__pt) == experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
	operator!=(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
	return experimental::get_underlying(__pt) != experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
	operator<(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
	return experimental::get_underlying(__pt) < experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
	operator>(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
	return experimental::get_underlying(__pt) > experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
	operator<=(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
	return experimental::get_underlying(__pt) <= experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool
	operator>=(const propagate_const<_Tp>& __pt, const propagate_const<_Up>& __pu) {
	return experimental::get_underlying(__pt) >= experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(const propagate_const<_Tp>& __pt, const _Up& __u) {
	return experimental::get_underlying(__pt) == __u;
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(const propagate_const<_Tp>& __pt, const _Up& __u) {
	return experimental::get_underlying(__pt) != __u;
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<(const propagate_const<_Tp>& __pt, const _Up& __u) {
	return experimental::get_underlying(__pt) < __u;
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>(const propagate_const<_Tp>& __pt, const _Up& __u) {
	return experimental::get_underlying(__pt) > __u;
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<=(const propagate_const<_Tp>& __pt, const _Up& __u) {
	return experimental::get_underlying(__pt) <= __u;
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>=(const propagate_const<_Tp>& __pt, const _Up& __u) {
	return experimental::get_underlying(__pt) >= __u;
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator==(const _Tp& __t, const propagate_const<_Up>& __pu) {
	return __t == experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator!=(const _Tp& __t, const propagate_const<_Up>& __pu) {
	return __t != experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<(const _Tp& __t, const propagate_const<_Up>& __pu) {
	return __t < experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>(const _Tp& __t, const propagate_const<_Up>& __pu) {
	return __t > experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator<=(const _Tp& __t, const propagate_const<_Up>& __pu) {
	return __t <= experimental::get_underlying(__pu);
	}

	template <class _Tp, class _Up>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool operator>=(const _Tp& __t, const propagate_const<_Up>& __pu) {
	return __t >= experimental::get_underlying(__pu);
	}

	template <class _Tp>
	_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR void swap(propagate_const<_Tp>& __pc1, propagate_const<_Tp>& __pc2)
	_NOEXCEPT_(__is_nothrow_swappable<_Tp>::value) {
	__pc1.swap(__pc2);
	}

	template <class _Tp>
	_LIBCPP_CONSTEXPR const _Tp& get_underlying(const propagate_const<_Tp>& __pt) _NOEXCEPT {
	return __pt.__t_;
	}

	template <class _Tp>
	_LIBCPP_CONSTEXPR _Tp& get_underlying(propagate_const<_Tp>& __pt) _NOEXCEPT {
	return __pt.__t_;
	}

	_LIBCPP_END_NAMESPACE_LFTS_V2

	_LIBCPP_BEGIN_NAMESPACE_STD

	template <class _Tp>
	struct hash<experimental::propagate_const<_Tp>> {
	typedef size_t result_type;
	typedef experimental::propagate_const<_Tp> argument_type;

	_LIBCPP_HIDE_FROM_ABI size_t operator()(const experimental::propagate_const<_Tp>& __pc1) const {
	return std::hash<_Tp>()(experimental::get_underlying(__pc1));
	}
	};

	template <class _Tp>
	struct equal_to<experimental::propagate_const<_Tp>> {
	typedef experimental::propagate_const<_Tp> first_argument_type;
	typedef experimental::propagate_const<_Tp> second_argument_type;

	_LIBCPP_HIDE_FROM_ABI bool
	operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
	return std::equal_to<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
	}
	};

	template <class _Tp>
	struct not_equal_to<experimental::propagate_const<_Tp>> {
	typedef experimental::propagate_const<_Tp> first_argument_type;
	typedef experimental::propagate_const<_Tp> second_argument_type;

	_LIBCPP_HIDE_FROM_ABI bool
	operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
	return std::not_equal_to<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
	}
	};

	template <class _Tp>
	struct less<experimental::propagate_const<_Tp>> {
	typedef experimental::propagate_const<_Tp> first_argument_type;
	typedef experimental::propagate_const<_Tp> second_argument_type;

	_LIBCPP_HIDE_FROM_ABI bool
	operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
	return std::less<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
	}
	};

	template <class _Tp>
	struct greater<experimental::propagate_const<_Tp>> {
	typedef experimental::propagate_const<_Tp> first_argument_type;
	typedef experimental::propagate_const<_Tp> second_argument_type;

	_LIBCPP_HIDE_FROM_ABI bool
	operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
	return std::greater<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
	}
	};

	template <class _Tp>
	struct less_equal<experimental::propagate_const<_Tp>> {
	typedef experimental::propagate_const<_Tp> first_argument_type;
	typedef experimental::propagate_const<_Tp> second_argument_type;

	_LIBCPP_HIDE_FROM_ABI bool
	operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
	return std::less_equal<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
	}
	};

	template <class _Tp>
	struct greater_equal<experimental::propagate_const<_Tp>> {
	typedef experimental::propagate_const<_Tp> first_argument_type;
	typedef experimental::propagate_const<_Tp> second_argument_type;

	_LIBCPP_HIDE_FROM_ABI bool
	operator()(const experimental::propagate_const<_Tp>& __pc1, const experimental::propagate_const<_Tp>& __pc2) const {
	return std::greater_equal<_Tp>()(experimental::get_underlying(__pc1), experimental::get_underlying(__pc2));
	}
	};

	_LIBCPP_END_NAMESPACE_STD

	#endif // _LIBCPP_STD_VER >= 14

	_LIBCPP_POP_MACROS

	#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
	# include <type_traits>
	#endif

	#endif // _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST