cuda_toolkit/include/__iterator/concepts.h

// -*- 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
// SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCUDACXX___ITERATOR_CONCEPTS_H
#define _LIBCUDACXX___ITERATOR_CONCEPTS_H

#ifndef __cuda_std__
#include <__config>
#endif //__cuda_std__

#include "../__concepts/arithmetic.h"
#include "../__concepts/assignable.h"
#include "../__concepts/common_reference_with.h"
#include "../__concepts/constructible.h"
#include "../__concepts/copyable.h"
#include "../__concepts/derived_from.h"
#include "../__concepts/equality_comparable.h"
#include "../__concepts/invocable.h"
#include "../__concepts/movable.h"
#include "../__concepts/predicate.h"
#include "../__concepts/regular.h"
#include "../__concepts/relation.h"
#include "../__concepts/same_as.h"
#include "../__concepts/semiregular.h"
#include "../__concepts/totally_ordered.h"
#include "../__functional/invoke.h"
#include "../__iterator/incrementable_traits.h"
#include "../__iterator/iter_move.h"
#include "../__iterator/iterator_traits.h"
#include "../__iterator/readable_traits.h"
#include "../__memory/pointer_traits.h"
#include "../__utility/forward.h"
#include "../__type_traits/add_pointer.h"
#include "../__type_traits/common_reference.h"
#include "../__type_traits/conjunction.h"
#include "../__type_traits/enable_if.h"
#include "../__type_traits/remove_cv.h"
#include "../__type_traits/remove_cvref.h"
#include "../__type_traits/void_t.h"

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

_LIBCUDACXX_BEGIN_NAMESPACE_STD

#if _LIBCUDACXX_STD_VER > 17

// [iterator.concept.readable]
template<class _In>
concept __indirectly_readable_impl =
  requires(const _In __i) {
    typename iter_value_t<_In>;
    typename iter_reference_t<_In>;
    typename iter_rvalue_reference_t<_In>;
    { *__i } -> same_as<iter_reference_t<_In>>;
    { _CUDA_VRANGES::iter_move(__i) } -> same_as<iter_rvalue_reference_t<_In>>;
  } &&
  common_reference_with<iter_reference_t<_In>&&, iter_value_t<_In>&> &&
  common_reference_with<iter_reference_t<_In>&&, iter_rvalue_reference_t<_In>&&> &&
  common_reference_with<iter_rvalue_reference_t<_In>&&, const iter_value_t<_In>&>;

template<class _In>
concept indirectly_readable = __indirectly_readable_impl<remove_cvref_t<_In>>;

template<indirectly_readable _Tp>
using iter_common_reference_t = common_reference_t<iter_reference_t<_Tp>, iter_value_t<_Tp>&>;

// [iterator.concept.writable]
template<class _Out, class _Tp>
concept indirectly_writable =
  requires(_Out&& __o, _Tp&& __t) {
    *__o = _CUDA_VSTD::forward<_Tp>(__t);                        // not required to be equality-preserving
    *_CUDA_VSTD::forward<_Out>(__o) = _CUDA_VSTD::forward<_Tp>(__t);  // not required to be equality-preserving
    const_cast<const iter_reference_t<_Out>&&>(*__o) = _CUDA_VSTD::forward<_Tp>(__t);                       // not required to be equality-preserving
    const_cast<const iter_reference_t<_Out>&&>(*_CUDA_VSTD::forward<_Out>(__o)) = _CUDA_VSTD::forward<_Tp>(__t); // not required to be equality-preserving
  };

// [iterator.concept.winc]
template<class _Tp>
concept __integer_like = integral<_Tp> && !same_as<_Tp, bool>;

template<class _Tp>
concept __signed_integer_like = signed_integral<_Tp>;

template<class _Ip>
concept weakly_incrementable =
  // TODO: remove this once the clang bug is fixed (bugs.llvm.org/PR48173).
  !same_as<_Ip, bool> && // Currently, clang does not handle bool correctly.
  movable<_Ip> &&
  requires(_Ip __i) {
    typename iter_difference_t<_Ip>;
    requires __signed_integer_like<iter_difference_t<_Ip>>;
    { ++__i } -> same_as<_Ip&>;   // not required to be equality-preserving
    __i++;                        // not required to be equality-preserving
  };

// [iterator.concept.inc]
template<class _Ip>
concept incrementable =
  regular<_Ip> &&
  weakly_incrementable<_Ip> &&
  requires(_Ip __i) {
    { __i++ } -> same_as<_Ip>;
  };

// [iterator.concept.iterator]
template<class _Ip>
concept input_or_output_iterator =
  requires(_Ip __i) {
    { *__i } -> __can_reference;
  } &&
  weakly_incrementable<_Ip>;

// [iterator.concept.sentinel]
template<class _Sp, class _Ip>
concept sentinel_for =
  semiregular<_Sp> &&
  input_or_output_iterator<_Ip> &&
  __weakly_equality_comparable_with<_Sp, _Ip>;

template<class, class>
inline constexpr bool disable_sized_sentinel_for = false;

template<class _Sp, class _Ip>
concept sized_sentinel_for =
  sentinel_for<_Sp, _Ip> &&
  !disable_sized_sentinel_for<remove_cv_t<_Sp>, remove_cv_t<_Ip>> &&
  requires(const _Ip& __i, const _Sp& __s) {
    { __s - __i } -> same_as<iter_difference_t<_Ip>>;
    { __i - __s } -> same_as<iter_difference_t<_Ip>>;
  };

// [iterator.concept.input]
template<class _Ip>
concept input_iterator =
  input_or_output_iterator<_Ip> &&
  indirectly_readable<_Ip> &&
  requires { typename _ITER_CONCEPT<_Ip>; } &&
  derived_from<_ITER_CONCEPT<_Ip>, input_iterator_tag>;

// [iterator.concept.output]
template<class _Ip, class _Tp>
concept output_iterator =
  input_or_output_iterator<_Ip> &&
  indirectly_writable<_Ip, _Tp> &&
  requires (_Ip __it, _Tp&& __t) {
    *__it++ = _CUDA_VSTD::forward<_Tp>(__t); // not required to be equality-preserving
  };

// [iterator.concept.forward]
template<class _Ip>
concept forward_iterator =
  input_iterator<_Ip> &&
  derived_from<_ITER_CONCEPT<_Ip>, forward_iterator_tag> &&
  incrementable<_Ip> &&
  sentinel_for<_Ip, _Ip>;

// [iterator.concept.bidir]
template<class _Ip>
concept bidirectional_iterator =
  forward_iterator<_Ip> &&
  derived_from<_ITER_CONCEPT<_Ip>, bidirectional_iterator_tag> &&
  requires(_Ip __i) {
    { --__i } -> same_as<_Ip&>;
    { __i-- } -> same_as<_Ip>;
  };

template<class _Ip>
concept random_access_iterator =
  bidirectional_iterator<_Ip> &&
  derived_from<_ITER_CONCEPT<_Ip>, random_access_iterator_tag> &&
  totally_ordered<_Ip> &&
  sized_sentinel_for<_Ip, _Ip> &&
  requires(_Ip __i, const _Ip __j, const iter_difference_t<_Ip> __n) {
    { __i += __n } -> same_as<_Ip&>;
    { __j +  __n } -> same_as<_Ip>;
    { __n +  __j } -> same_as<_Ip>;
    { __i -= __n } -> same_as<_Ip&>;
    { __j -  __n } -> same_as<_Ip>;
    {  __j[__n]  } -> same_as<iter_reference_t<_Ip>>;
  };

template<class _Ip>
concept contiguous_iterator =
  random_access_iterator<_Ip> &&
  derived_from<_ITER_CONCEPT<_Ip>, contiguous_iterator_tag> &&
  is_lvalue_reference_v<iter_reference_t<_Ip>> &&
  same_as<iter_value_t<_Ip>, remove_cvref_t<iter_reference_t<_Ip>>> &&
  requires(const _Ip& __i) {
    { _CUDA_VSTD::to_address(__i) } -> same_as<add_pointer_t<iter_reference_t<_Ip>>>;
  };

template<class _Ip>
concept __has_arrow = input_iterator<_Ip> && (is_pointer_v<_Ip> || requires(_Ip __i) { __i.operator->(); });

template<class _Ip>
concept __has_const_arrow = (is_pointer_v<_Ip> || requires(const _Ip __i) { __i.operator->(); });

// [indirectcallable.indirectinvocable]
template<class _Fp, class _It>
concept indirectly_unary_invocable =
  indirectly_readable<_It> &&
  copy_constructible<_Fp> &&
  invocable<_Fp&, iter_value_t<_It>&> &&
  invocable<_Fp&, iter_reference_t<_It>> &&
  invocable<_Fp&, iter_common_reference_t<_It>> &&
  common_reference_with<
    invoke_result_t<_Fp&, iter_value_t<_It>&>,
    invoke_result_t<_Fp&, iter_reference_t<_It>>>;

template<class _Fp, class _It>
concept indirectly_regular_unary_invocable =
  indirectly_readable<_It> &&
  copy_constructible<_Fp> &&
  regular_invocable<_Fp&, iter_value_t<_It>&> &&
  regular_invocable<_Fp&, iter_reference_t<_It>> &&
  regular_invocable<_Fp&, iter_common_reference_t<_It>> &&
  common_reference_with<
    invoke_result_t<_Fp&, iter_value_t<_It>&>,
    invoke_result_t<_Fp&, iter_reference_t<_It>>>;

template<class _Fp, class _It>
concept indirect_unary_predicate =
  indirectly_readable<_It> &&
  copy_constructible<_Fp> &&
  predicate<_Fp&, iter_value_t<_It>&> &&
  predicate<_Fp&, iter_reference_t<_It>> &&
  predicate<_Fp&, iter_common_reference_t<_It>>;

template<class _Fp, class _It1, class _It2>
concept indirect_binary_predicate =
  indirectly_readable<_It1> && indirectly_readable<_It2> &&
  copy_constructible<_Fp> &&
  predicate<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&> &&
  predicate<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>> &&
  predicate<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&> &&
  predicate<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>> &&
  predicate<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>;

template<class _Fp, class _It1, class _It2 = _It1>
concept indirect_equivalence_relation =
  indirectly_readable<_It1> && indirectly_readable<_It2> &&
  copy_constructible<_Fp> &&
  equivalence_relation<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&> &&
  equivalence_relation<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>> &&
  equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&> &&
  equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>> &&
  equivalence_relation<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>;

template<class _Fp, class _It1, class _It2 = _It1>
concept indirect_strict_weak_order =
  indirectly_readable<_It1> && indirectly_readable<_It2> &&
  copy_constructible<_Fp> &&
  strict_weak_order<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&> &&
  strict_weak_order<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>> &&
  strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&> &&
  strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>> &&
  strict_weak_order<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>;

template<class _Fp, class... _Its>
  requires (indirectly_readable<_Its> && ...) && invocable<_Fp, iter_reference_t<_Its>...>
using indirect_result_t = invoke_result_t<_Fp, iter_reference_t<_Its>...>;

template<class _In, class _Out>
concept indirectly_movable =
  indirectly_readable<_In> &&
  indirectly_writable<_Out, iter_rvalue_reference_t<_In>>;

template<class _In, class _Out>
concept indirectly_movable_storable =
  indirectly_movable<_In, _Out> &&
  indirectly_writable<_Out, iter_value_t<_In>> &&
  movable<iter_value_t<_In>> &&
  constructible_from<iter_value_t<_In>, iter_rvalue_reference_t<_In>> &&
  assignable_from<iter_value_t<_In>&, iter_rvalue_reference_t<_In>>;

template<class _In, class _Out>
concept indirectly_copyable =
  indirectly_readable<_In> &&
  indirectly_writable<_Out, iter_reference_t<_In>>;

template<class _In, class _Out>
concept indirectly_copyable_storable =
  indirectly_copyable<_In, _Out> &&
  indirectly_writable<_Out, iter_value_t<_In>&> &&
  indirectly_writable<_Out, const iter_value_t<_In>&> &&
  indirectly_writable<_Out, iter_value_t<_In>&&> &&
  indirectly_writable<_Out, const iter_value_t<_In>&&> &&
  copyable<iter_value_t<_In>> &&
  constructible_from<iter_value_t<_In>, iter_reference_t<_In>> &&
  assignable_from<iter_value_t<_In>&, iter_reference_t<_In>>;

// Note: indirectly_swappable is located in iter_swap.h to prevent a dependency cycle
// (both iter_swap and indirectly_swappable require indirectly_readable).

#elif _LIBCUDACXX_STD_VER > 14

// [iterator.concept.readable]
template<class _In>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_readable_impl_,
  requires(const _In __i)(
    typename(iter_value_t<_In>),
    typename(iter_reference_t<_In>),
    typename(iter_rvalue_reference_t<_In>),
    requires(same_as<iter_reference_t<_In>, decltype(*__i)>),
    requires(same_as<iter_rvalue_reference_t<_In>, decltype(_CUDA_VRANGES::iter_move(__i))>),
    requires(common_reference_with<iter_reference_t<_In>&&, iter_value_t<_In>&>),
    requires(common_reference_with<iter_reference_t<_In>&&, iter_rvalue_reference_t<_In>&&>),
    requires(common_reference_with<iter_rvalue_reference_t<_In>&&, const iter_value_t<_In>&>)
  ));

template<class _In>
_LIBCUDACXX_CONCEPT indirectly_readable = _LIBCUDACXX_FRAGMENT(__indirectly_readable_impl_, remove_cvref_t<_In>);

template<class _Tp>
using iter_common_reference_t = enable_if_t<indirectly_readable<_Tp>,
                                  common_reference_t<iter_reference_t<_Tp>, iter_value_t<_Tp>&>>;
// [iterator.concept.writable]
template<class _Out, class _Tp>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_writable_,
  requires(_Out&& __o, _Tp&& __t)(
    typename(decltype(*__o = _CUDA_VSTD::forward<_Tp>(__t))),
    typename(decltype(*_CUDA_VSTD::forward<_Out>(__o) = _CUDA_VSTD::forward<_Tp>(__t))),
    typename(decltype(const_cast<const iter_reference_t<_Out>&&>(*__o) = _CUDA_VSTD::forward<_Tp>(__t))),
    typename(decltype(const_cast<const iter_reference_t<_Out>&&>(*_CUDA_VSTD::forward<_Out>(__o)) = _CUDA_VSTD::forward<_Tp>(__t)))
  ));

template<class _Out, class _Tp>
_LIBCUDACXX_CONCEPT indirectly_writable = _LIBCUDACXX_FRAGMENT(__indirectly_writable_, _Out, _Tp);

// [iterator.concept.winc]
template<class _Tp>
_LIBCUDACXX_CONCEPT __integer_like = integral<_Tp> && !same_as<_Tp, bool>;

template<class _Tp>
_LIBCUDACXX_CONCEPT __signed_integer_like = signed_integral<_Tp>;

template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __weakly_incrementable_,
  requires(_Ip __i)(
    typename(iter_difference_t<_Ip>),
    requires(!same_as<_Ip, bool>),
    requires(movable<_Ip>),
    requires(__signed_integer_like<iter_difference_t<_Ip>>),
    requires(same_as<_Ip&, decltype(++__i)>),
    (__i++)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT weakly_incrementable = _LIBCUDACXX_FRAGMENT(__weakly_incrementable_, _Ip);

// [iterator.concept.inc]
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __incrementable_,
  requires(_Ip __i)(
    requires(regular<_Ip>),
    requires(weakly_incrementable<_Ip>),
    requires(same_as<_Ip, decltype(__i++)>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT incrementable = _LIBCUDACXX_FRAGMENT(__incrementable_, _Ip);

// [iterator.concept.iterator]
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __input_or_output_iterator_,
  requires(_Ip __i)(
    requires(weakly_incrementable<_Ip>),
    requires(__can_reference<decltype(*__i)>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT input_or_output_iterator = _LIBCUDACXX_FRAGMENT(__input_or_output_iterator_, _Ip);

// [iterator.concept.sentinel]
template<class _Sp, class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __sentinel_for_,
  requires()(
    requires(semiregular<_Sp>),
    requires(input_or_output_iterator<_Ip>),
    requires(__weakly_equality_comparable_with<_Sp, _Ip>)
  ));

template<class _Sp, class _Ip>
_LIBCUDACXX_CONCEPT sentinel_for = _LIBCUDACXX_FRAGMENT(__sentinel_for_, _Sp, _Ip);

template<class, class>
_LIBCUDACXX_INLINE_VAR constexpr bool disable_sized_sentinel_for = false;

template<class _Sp, class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __sized_sentinel_for_,
  requires(const _Ip& __i, const _Sp& __s)(
    requires(sentinel_for<_Sp, _Ip>),
    requires(!disable_sized_sentinel_for<remove_cv_t<_Sp>, remove_cv_t<_Ip>>),
    requires(same_as<iter_difference_t<_Ip>, decltype(__s - __i)>),
    requires(same_as<iter_difference_t<_Ip>, decltype(__i - __s)>)
  ));

template<class _Sp, class _Ip>
_LIBCUDACXX_CONCEPT sized_sentinel_for = _LIBCUDACXX_FRAGMENT(__sized_sentinel_for_, _Sp, _Ip);

// [iterator.concept.input]
// NOTE: The ordering here is load bearing. MSVC has issues with finding iterator_traits
//       We can work around this by checking other constraints first
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __input_iterator_,
  requires()(
    requires(input_or_output_iterator<_Ip>),
    requires(indirectly_readable<_Ip>),
    typename(_ITER_CONCEPT<_Ip>),
    requires(derived_from<_ITER_CONCEPT<_Ip>, input_iterator_tag>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT input_iterator = _LIBCUDACXX_FRAGMENT(__input_iterator_, _Ip);

// [iterator.concept.output]
template<class _Ip, class _Tp>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __output_iterator_,
  requires(_Ip __it, _Tp&& __t)(
    requires(input_or_output_iterator<_Ip>),
    requires(indirectly_writable<_Ip, _Tp>),
    (*__it++ = _CUDA_VSTD::forward<_Tp>(__t))
  ));

template<class _Ip, class _Tp>
_LIBCUDACXX_CONCEPT output_iterator = _LIBCUDACXX_FRAGMENT(__output_iterator_, _Ip, _Tp);

// [iterator.concept.forward]
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __forward_iterator_,
  requires()(
    requires(input_iterator<_Ip>),
    requires(derived_from<_ITER_CONCEPT<_Ip>, forward_iterator_tag>),
    requires(incrementable<_Ip>),
    requires(sentinel_for<_Ip, _Ip>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT forward_iterator = _LIBCUDACXX_FRAGMENT(__forward_iterator_, _Ip);

// [iterator.concept.bidir]
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __bidirectional_iterator_,
  requires(_Ip __i)(
    requires(forward_iterator<_Ip>),
    requires(derived_from<_ITER_CONCEPT<_Ip>, bidirectional_iterator_tag>),
    requires(same_as<_Ip&, decltype(--__i)>),
    requires(same_as<_Ip, decltype(__i--)>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT bidirectional_iterator = _LIBCUDACXX_FRAGMENT(__bidirectional_iterator_, _Ip);

// [iterator.concept.random.access]
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __random_access_iterator_operations_,
  requires(_Ip __i, const _Ip __j, const iter_difference_t<_Ip> __n)(
    requires(same_as<_Ip&, decltype(__i += __n)>),
    requires(same_as<_Ip,  decltype(__j +  __n)>),
    requires(same_as<_Ip,  decltype(__n +  __j)>),
    requires(same_as<_Ip&, decltype(__i -= __n)>),
    requires(same_as<_Ip,  decltype(__j -  __n)>),
    requires(same_as<iter_reference_t<_Ip>, decltype(__j[__n])>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT __random_access_iterator_operations = _LIBCUDACXX_FRAGMENT(__random_access_iterator_operations_, _Ip);

template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __random_access_iterator_,
  requires()(
    requires(bidirectional_iterator<_Ip>),
    requires(derived_from<_ITER_CONCEPT<_Ip>, random_access_iterator_tag>),
    requires(totally_ordered<_Ip>),
    requires(sized_sentinel_for<_Ip, _Ip>),
    requires(__random_access_iterator_operations<_Ip>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT random_access_iterator = _LIBCUDACXX_FRAGMENT(__random_access_iterator_, _Ip);

// [iterator.concept.contiguous]
template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __contiguous_iterator_,
  requires(const _Ip& __i)(
    requires(random_access_iterator<_Ip>),
    requires(derived_from<_ITER_CONCEPT<_Ip>, contiguous_iterator_tag>),
    requires(is_lvalue_reference_v<iter_reference_t<_Ip>>),
    requires(same_as<iter_value_t<_Ip>, remove_cvref_t<iter_reference_t<_Ip>>>),
    requires(same_as<add_pointer_t<iter_reference_t<_Ip>>,  decltype(_CUDA_VSTD::to_address(__i))>)
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT contiguous_iterator = _LIBCUDACXX_FRAGMENT(__contiguous_iterator_, _Ip);

template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __has_arrow_,
  requires(_Ip __i)(
    (__i.operator->())
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT __has_arrow = input_iterator<_Ip>
  && (is_pointer_v<_Ip> || _LIBCUDACXX_FRAGMENT(__has_arrow_, _Ip));

template<class _Ip>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __has_const_arrow_,
  requires(const _Ip __i)(
    (__i.operator->())
  ));

template<class _Ip>
_LIBCUDACXX_CONCEPT __has_const_arrow = (is_pointer_v<_Ip> || _LIBCUDACXX_FRAGMENT(__has_const_arrow_, _Ip));

// [indirectcallable.indirectinvocable]
template<class _Fp, class _It>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_unary_invocable,
  requires()(
    requires(indirectly_readable<_It>),
    requires(copy_constructible<_Fp>),
    requires(invocable<_Fp&, iter_value_t<_It>&>),
    requires(invocable<_Fp&, iter_reference_t<_It>>),
    requires(invocable<_Fp&, iter_common_reference_t<_It>>),
    requires(common_reference_with<invoke_result_t<_Fp&, iter_value_t<_It>&>,
                                   invoke_result_t<_Fp&, iter_reference_t<_It>>>)
  ));

template<class _Fp, class _It>
_LIBCUDACXX_CONCEPT indirectly_unary_invocable = _LIBCUDACXX_FRAGMENT(__indirectly_unary_invocable, _Fp, _It);

template<class _Fp, class _It>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_regular_unary_invocable_,
  requires()(
    requires(indirectly_readable<_It>),
    requires(copy_constructible<_Fp>),
    requires(regular_invocable<_Fp&, iter_value_t<_It>&>),
    requires(regular_invocable<_Fp&, iter_reference_t<_It>>),
    requires(regular_invocable<_Fp&, iter_common_reference_t<_It>>),
    requires(common_reference_with<invoke_result_t<_Fp&, iter_value_t<_It>&>,
                                   invoke_result_t<_Fp&, iter_reference_t<_It>>>)
  ));

template<class _Fp, class _It>
_LIBCUDACXX_CONCEPT indirectly_regular_unary_invocable = _LIBCUDACXX_FRAGMENT(__indirectly_regular_unary_invocable_, _Fp, _It);

template<class _Fp, class _It>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirect_unary_predicate_,
  requires()(
    requires(indirectly_readable<_It>),
    requires(copy_constructible<_Fp>),
    requires(predicate<_Fp&, iter_value_t<_It>&>),
    requires(predicate<_Fp&, iter_reference_t<_It>>),
    requires(predicate<_Fp&, iter_common_reference_t<_It>>)
  ));

template<class _Fp, class _It>
_LIBCUDACXX_CONCEPT indirect_unary_predicate = _LIBCUDACXX_FRAGMENT(__indirect_unary_predicate_, _Fp, _It);

template<class _Fp, class _It1, class _It2>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirect_binary_predicate_,
  requires()(
    requires(indirectly_readable<_It1>),
    requires(indirectly_readable<_It2>),
    requires(copy_constructible<_Fp>),
    requires(predicate<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&>),
    requires(predicate<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>>),
    requires(predicate<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&>),
    requires(predicate<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>>),
    requires(predicate<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>)
  ));

template<class _Fp, class _It1, class _It2>
_LIBCUDACXX_CONCEPT indirect_binary_predicate = _LIBCUDACXX_FRAGMENT(__indirect_binary_predicate_, _Fp, _It1, _It2);

template<class _Fp, class _It1, class _It2>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirect_equivalence_relation_,
  requires()(
    requires(indirectly_readable<_It1>),
    requires(indirectly_readable<_It2>),
    requires(copy_constructible<_Fp>),
    requires(equivalence_relation<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&>),
    requires(equivalence_relation<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>>),
    requires(equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&>),
    requires(equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>>),
    requires(equivalence_relation<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>)
  ));

template<class _Fp, class _It1, class _It2 = _It1>
_LIBCUDACXX_CONCEPT indirect_equivalence_relation = _LIBCUDACXX_FRAGMENT(__indirect_equivalence_relation_, _Fp, _It1, _It2);

template<class _Fp, class _It1, class _It2>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirect_strict_weak_order_,
  requires()(
    requires(indirectly_readable<_It1>),
    requires(indirectly_readable<_It2>),
    requires(copy_constructible<_Fp>),
    requires(strict_weak_order<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&>),
    requires(strict_weak_order<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>>),
    requires(strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&>),
    requires(strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>>),
    requires(strict_weak_order<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>)
  ));

template<class _Fp, class _It1, class _It2 = _It1>
_LIBCUDACXX_CONCEPT indirect_strict_weak_order = _LIBCUDACXX_FRAGMENT(__indirect_strict_weak_order_, _Fp, _It1, _It2);

#if _LIBCUDACXX_STD_VER > 14
template<class _Fp, class... _Its>
using indirect_result_t = enable_if_t<(indirectly_readable<_Its> && ...) && invocable<_Fp, iter_reference_t<_Its>...>, invoke_result_t<_Fp, iter_reference_t<_Its>...>>;
#else
template<class _Fp, class... _Its>
using indirect_result_t = enable_if_t<conjunction_v<bool_constant<indirectly_readable<_Its>>...>
                                      && invocable<_Fp, iter_reference_t<_Its>...>,
                                      invoke_result_t<_Fp, iter_reference_t<_Its>...>>;
#endif // _LIBCUDACXX_STD_VER > 14

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_movable_,
  requires()(
    requires(indirectly_readable<_In>),
    requires(indirectly_writable<_Out, iter_rvalue_reference_t<_In>>)
  ));

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT indirectly_movable = _LIBCUDACXX_FRAGMENT(__indirectly_movable_, _In, _Out);

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_movable_storable_,
  requires()(
    requires(indirectly_movable<_In, _Out>),
    requires(indirectly_writable<_Out, iter_value_t<_In>>),
    requires(movable<iter_value_t<_In>>),
    requires(constructible_from<iter_value_t<_In>, iter_rvalue_reference_t<_In>>),
    requires(assignable_from<iter_value_t<_In>&, iter_rvalue_reference_t<_In>>)
  ));

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT indirectly_movable_storable = _LIBCUDACXX_FRAGMENT(__indirectly_movable_storable_, _In, _Out);

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_copyable_,
  requires()(
    requires(indirectly_readable<_In>),
    requires(indirectly_writable<_Out, iter_reference_t<_In>>)
  ));

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT indirectly_copyable = _LIBCUDACXX_FRAGMENT(__indirectly_copyable_, _In, _Out);

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __indirectly_copyable_storable_,
  requires()(
    requires(indirectly_copyable<_In, _Out>),
    requires(indirectly_writable<_Out, iter_value_t<_In>&>),
    requires(indirectly_writable<_Out, const iter_value_t<_In>&>),
    requires(indirectly_writable<_Out, iter_value_t<_In>&&>),
    requires(indirectly_writable<_Out, const iter_value_t<_In>&&>),
    requires(copyable<iter_value_t<_In>>),
    requires(constructible_from<iter_value_t<_In>, iter_reference_t<_In>>),
    requires(assignable_from<iter_value_t<_In>&, iter_reference_t<_In>>)
  ));

template<class _In, class _Out>
_LIBCUDACXX_CONCEPT indirectly_copyable_storable =_LIBCUDACXX_FRAGMENT(__indirectly_copyable_storable_, _In, _Out);

template<class _Ip, class = void>
_LIBCUDACXX_INLINE_VAR constexpr bool __has_iter_category = false;

template<class _Ip>
_LIBCUDACXX_INLINE_VAR constexpr bool __has_iter_category<_Ip, void_t<typename _Ip::iterator_category>> = true;

template<class _Ip, class = void>
_LIBCUDACXX_INLINE_VAR constexpr bool __has_iter_concept = false;

template<class _Ip>
_LIBCUDACXX_INLINE_VAR constexpr bool __has_iter_concept<_Ip, void_t<typename _Ip::iterator_concept>> = true;

#endif // _LIBCUDACXX_STD_VER > 14

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___ITERATOR_CONCEPTS_H