[libc++][ranges] Implement ranges::find{, _if, _if_not}

Reviewed By: var-const, #libc, ldionne

Spies: ldionne, tcanens, libcxx-commits, mgorny

Differential Revision: https://reviews.llvm.org/D121248

libcxx/docs/Status/RangesAlgorithms.csv

@@ -2,9 +2,9 @@ Category,Algorithm,Assignee,CL,Complete
 Search,any_of,Christopher Di Bella,`D105793 <https://llvm.org/D105793>`_
 Search,all_of,Christopher Di Bella,`D105793 <https://llvm.org/D105793>`_
 Search,none_of,Christopher Di Bella,`D105793 <https://llvm.org/D105793>`_
-Search,find,Christopher Di Bella,`D105456 <https://llvm.org/D105456>`_
-Search,find_if,Christopher Di Bella,`D105792 <https://llvm.org/D105792>`_
-Search,find_if_not,Christopher Di Bella,`D105792 <https://llvm.org/D105792>`_
+Search,find,Nikolas Klauser,`D121248 <https://reviews.llvm.org/D121248>`_,✅
+Search,find_if,Nikolas Klauser,`D121248 <https://reviews.llvm.org/D121248>`_,✅
+Search,find_if_not,Nikolas Klauser,`D121248 <https://reviews.llvm.org/D121248>`_,✅
 Search,find_first_of,Not assigned,n/a,Not started
 Search,adjacent_find,Not assigned,n/a,Not started
 Search,mismatch,Nikolas Klauser,`D117817 <https://llvm.org/D117817>`,Complete

libcxx/include/CMakeLists.txt

@@ -66,6 +66,9 @@ set(files
   __algorithm/pop_heap.h
   __algorithm/prev_permutation.h
   __algorithm/push_heap.h
+  __algorithm/ranges_find.h
+  __algorithm/ranges_find_if.h
+  __algorithm/ranges_find_if_not.h
   __algorithm/ranges_max_element.h
   __algorithm/ranges_min_element.h
   __algorithm/ranges_mismatch.h

libcxx/include/__algorithm/ranges_find.h

@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_FIND_H
+#define _LIBCPP___ALGORITHM_RANGES_FIND_H
+
+#include <__algorithm/ranges_find_if.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__functional/ranges_operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/projected.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
+#include <__utility/forward.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __find {
+struct __fn {
+  template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, class _Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<_Ip, _Proj>, const _Tp*>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  _Ip operator()(_Ip __first, _Sp __last, const _Tp& __value, _Proj __proj = {}) const {
+    auto __pred = [&](auto&& __e) { return std::forward<decltype(__e)>(__e) == __value; };
+    return ranges::__find_if_impl(std::move(__first), std::move(__last), __pred, __proj);
+  }
+
+  template <input_range _Rp, class _Tp, class _Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Rp>, _Proj>, const _Tp*>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  borrowed_iterator_t<_Rp> operator()(_Rp&& __r, const _Tp& __value, _Proj __proj = {}) const {
+    auto __pred = [&](auto&& __e) { return std::forward<decltype(__e)>(__e) == __value; };
+    return ranges::__find_if_impl(ranges::begin(__r), ranges::end(__r), __pred, __proj);
+  }
+};
+} // namespace __find
+
+inline namespace __cpo {
+  inline constexpr auto find = __find::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // _LIBCPP___ALGORITHM_RANGES_FIND_H

libcxx/include/__algorithm/ranges_find_if.h

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_FIND_IF_H
+#define _LIBCPP___ALGORITHM_RANGES_FIND_IF_H
+
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__functional/ranges_operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/projected.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+
+template <class _Ip, class _Sp, class _Pred, class _Proj>
+_LIBCPP_HIDE_FROM_ABI static constexpr
+_Ip __find_if_impl(_Ip __first, _Sp __last, _Pred& __pred, _Proj& __proj) {
+  for (; __first != __last; ++__first) {
+    if (std::invoke(__pred, std::invoke(__proj, *__first)))
+      break;
+  }
+  return __first;
+}
+
+namespace __find_if {
+struct __fn {
+
+  template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
+            indirect_unary_predicate<projected<_Ip, _Proj>> _Pred>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  _Ip operator()(_Ip __first, _Sp __last, _Pred __pred, _Proj __proj = {}) const {
+    return ranges::__find_if_impl(std::move(__first), std::move(__last), __pred, __proj);
+  }
+
+  template <input_range _Rp, class _Proj = identity,
+            indirect_unary_predicate<projected<iterator_t<_Rp>, _Proj>> _Pred>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Pred __pred, _Proj __proj = {}) const {
+    return ranges::__find_if_impl(ranges::begin(__r), ranges::end(__r), __pred, __proj);
+  }
+};
+} // namespace __find_if
+
+inline namespace __cpo {
+  inline constexpr auto find_if = __find_if::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // _LIBCPP___ALGORITHM_RANGES_FIND_IF_H

libcxx/include/__algorithm/ranges_find_if_not.h

@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_FIND_IF_NOT_H
+#define _LIBCPP___ALGORITHM_RANGES_FIND_IF_NOT_H
+
+#include <__algorithm/ranges_find_if.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__functional/ranges_operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/projected.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
+#include <__utility/forward.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __find_if_not {
+struct __fn {
+  template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
+            indirect_unary_predicate<projected<_Ip, _Proj>> _Pred>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  _Ip operator()(_Ip __first, _Sp __last, _Pred __pred, _Proj __proj = {}) const {
+    auto __pred2 = [&](auto&& __e) { return !std::invoke(__pred, std::forward<decltype(__e)>(__e)); };
+    return ranges::__find_if_impl(std::move(__first), std::move(__last), __pred2, __proj);
+  }
+
+  template <input_range _Rp, class _Proj = identity,
+            indirect_unary_predicate<projected<iterator_t<_Rp>, _Proj>> _Pred>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Pred __pred, _Proj __proj = {}) const {
+    auto __pred2 = [&](auto&& __e) { return !std::invoke(__pred, std::forward<decltype(__e)>(__e)); };
+    return ranges::__find_if_impl(ranges::begin(__r), ranges::end(__r), __pred2, __proj);
+  }
+};
+} // namespace __find_if_not
+
+inline namespace __cpo {
+  inline constexpr auto find_if_not = __find_if_not::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // _LIBCPP___ALGORITHM_RANGES_FIND_IF_NOT_H

libcxx/include/algorithm

@@ -56,6 +56,33 @@ namespace ranges {
     requires indirectly_comparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
   constexpr mismatch_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
   mismatch(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {})                           // since C++20
+
+  template<input_iterator I, sentinel_for<I> S, class T, class Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
+    constexpr I find(I first, S last, const T& value, Proj proj = {});              // since C++20
+
+  template<input_range R, class T, class Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
+    constexpr borrowed_iterator_t<R>
+      find(R&& r, const T& value, Proj proj = {});                                  // since C++20
+
+  template<input_iterator I, sentinel_for<I> S, class Proj = identity,
+           indirect_unary_predicate<projected<I, Proj>> Pred>
+    constexpr I find_if(I first, S last, Pred pred, Proj proj = {});                // since C++20
+
+  template<input_range R, class Proj = identity,
+           indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
+    constexpr borrowed_iterator_t<R>
+      find_if(R&& r, Pred pred, Proj proj = {});                                    // since C++20
+
+  template<input_iterator I, sentinel_for<I> S, class Proj = identity,
+           indirect_unary_predicate<projected<I, Proj>> Pred>
+    constexpr I find_if_not(I first, S last, Pred pred, Proj proj = {});            // since C++20
+
+  template<input_range R, class Proj = identity,
+           indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
+    constexpr borrowed_iterator_t<R>
+      find_if_not(R&& r, Pred pred, Proj proj = {});                                // since C++20
 }
 
 template <class InputIterator, class Predicate>
@@ -775,6 +802,9 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/pop_heap.h>
 #include <__algorithm/prev_permutation.h>
 #include <__algorithm/push_heap.h>
+#include <__algorithm/ranges_find.h>
+#include <__algorithm/ranges_find_if.h>
+#include <__algorithm/ranges_find_if_not.h>
 #include <__algorithm/ranges_max_element.h>
 #include <__algorithm/ranges_min_element.h>
 #include <__algorithm/ranges_mismatch.h>

libcxx/include/module.modulemap

@@ -294,6 +294,9 @@ module std [system] {
       module pop_heap                 { private header "__algorithm/pop_heap.h" }
       module prev_permutation         { private header "__algorithm/prev_permutation.h" }
       module push_heap                { private header "__algorithm/push_heap.h" }
+      module ranges_find              { private header "__algorithm/ranges_find.h" }
+      module ranges_find_if           { private header "__algorithm/ranges_find_if.h" }
+      module ranges_find_if_not       { private header "__algorithm/ranges_find_if_not.h" }
       module ranges_max_element       { private header "__algorithm/ranges_max_element.h" }
       module ranges_min_element       { private header "__algorithm/ranges_min_element.h" }
       module ranges_mismatch          { private header "__algorithm/ranges_mismatch.h" }

libcxx/test/libcxx/diagnostics/detail.headers/algorithm/ranges_find.module.verify.cpp

@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_find.h'}}
+#include <__algorithm/ranges_find.h>

libcxx/test/libcxx/diagnostics/detail.headers/algorithm/ranges_find_if.module.verify.cpp

@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_find_if.h'}}
+#include <__algorithm/ranges_find_if.h>

libcxx/test/libcxx/diagnostics/detail.headers/algorithm/ranges_find_if_not.module.verify.cpp

@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_find_if_not.h'}}
+#include <__algorithm/ranges_find_if_not.h>

libcxx/test/std/algorithms/alg.nonmodifying/alg.find/ranges.find.pass.cpp

@@ -0,0 +1,258 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// template<input_iterator I, sentinel_for<I> S, class T, class Proj = identity>
+//   requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
+//   constexpr I ranges::find(I first, S last, const T& value, Proj proj = {});
+// template<input_range R, class T, class Proj = identity>
+//   requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
+//   constexpr borrowed_iterator_t<R>
+//     ranges::find(R&& r, const T& value, Proj proj = {});
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+struct NotEqualityComparable {};
+
+template <class It, class Sent = It>
+concept HasFindIt = requires(It it, Sent sent) { std::ranges::find(it, sent, *it); };
+static_assert(HasFindIt<int*>);
+static_assert(!HasFindIt<NotEqualityComparable*>);
+static_assert(!HasFindIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasFindIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasFindIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasFindIt<cpp20_input_iterator<int*>, SentinelForNotSemiregular>);
+static_assert(!HasFindIt<cpp20_input_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+
+static_assert(!HasFindIt<int*, int>);
+static_assert(!HasFindIt<int, int*>);
+
+template <class Range, class ValT>
+concept HasFindR = requires(Range r) { std::ranges::find(r, ValT{}); };
+static_assert(HasFindR<std::array<int, 1>, int>);
+static_assert(!HasFindR<int, int>);
+static_assert(!HasFindR<std::array<NotEqualityComparable, 1>, NotEqualityComparable>);
+static_assert(!HasFindR<InputRangeNotDerivedFrom, int>);
+static_assert(!HasFindR<InputRangeNotIndirectlyReadable, int>);
+static_assert(!HasFindR<InputRangeNotInputOrOutputIterator, int>);
+static_assert(!HasFindR<InputRangeNotSentinelSemiregular, int>);
+static_assert(!HasFindR<InputRangeNotSentinelEqualityComparableWith, int>);
+
+template <class It, class Sent = It>
+constexpr void test_iterators() {
+  {
+    int a[] = {1, 2, 3, 4};
+    std::same_as<It> auto ret = std::ranges::find(It(a), Sent(It(a + 4)), 4);
+    assert(base(ret) == a + 3);
+    assert(*ret == 4);
+  }
+  {
+    int a[] = {1, 2, 3, 4};
+    auto range = std::ranges::subrange(It(a), Sent(It(a + 4)));
+    std::same_as<It> auto ret = std::ranges::find(range, 4);
+    assert(base(ret) == a + 3);
+    assert(*ret == 4);
+  }
+}
+
+struct OneWayComparable {
+  bool isLeft;
+  friend constexpr bool operator==(OneWayComparable l, OneWayComparable) { return l.isLeft; }
+};
+
+struct NonConstComparableLValue {
+  friend constexpr bool operator==(const NonConstComparableLValue&, const NonConstComparableLValue&) { return false; }
+  friend constexpr bool operator==(NonConstComparableLValue&, NonConstComparableLValue&) { return false; }
+  friend constexpr bool operator==(const NonConstComparableLValue&, NonConstComparableLValue&) { return false; }
+  friend constexpr bool operator==(NonConstComparableLValue&, const NonConstComparableLValue&) { return true; }
+};
+
+struct NonConstComparableRValue {
+  friend constexpr bool operator==(const NonConstComparableRValue&, const NonConstComparableRValue&) { return false; }
+  friend constexpr bool operator==(const NonConstComparableRValue&&, const NonConstComparableRValue&&) { return false; }
+  friend constexpr bool operator==(NonConstComparableRValue&&, NonConstComparableRValue&&) { return false; }
+  friend constexpr bool operator==(NonConstComparableRValue&&, const NonConstComparableRValue&) { return true; }
+};
+
+constexpr bool test() {
+  test_iterators<int*>();
+  test_iterators<const int*>();
+  test_iterators<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>();
+  test_iterators<bidirectional_iterator<int*>>();
+  test_iterators<forward_iterator<int*>>();
+  test_iterators<random_access_iterator<int*>>();
+  test_iterators<contiguous_iterator<int*>>();
+
+  {
+    // check that projections are used properly and that they are called with the iterator directly
+    {
+      int a[] = {1, 2, 3, 4};
+      auto ret = std::ranges::find(a, a + 4, a + 3, [](int& i) { return &i; });
+      assert(ret == a + 3);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      auto ret = std::ranges::find(a, a + 3, [](int& i) { return &i; });
+      assert(ret == a + 3);
+    }
+  }
+
+  { // check that the first element is returned
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::find(a, 0, &S::comp);
+      assert(ret == a);
+      assert(ret->comp == 0);
+      assert(ret->other == 0);
+    }
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::find(a, a + 3, 0, &S::comp);
+      assert(ret == a);
+      assert(ret->comp == 0);
+      assert(ret->other == 0);
+    }
+  }
+
+  { // check that end + 1 iterator is returned with no match
+    {
+      int a[] = {1, 1, 1};
+      auto ret = std::ranges::find(a, a + 3, 0);
+      assert(ret == a + 3);
+    }
+    {
+      int a[] = {1, 1, 1};
+      auto ret = std::ranges::find(a, 0);
+      assert(ret == a + 3);
+    }
+  }
+
+  {
+    // check that ranges::dangling is returned
+    [[maybe_unused]] std::same_as<std::ranges::dangling> auto ret =
+      std::ranges::find(std::array{1, 2}, 3);
+  }
+
+  {
+    // check that an iterator is returned with a borrowing range
+    int a[] = {1, 2, 3, 4};
+    std::same_as<int*> auto ret = std::ranges::find(std::views::all(a), 1);
+    assert(ret == a);
+    assert(*ret == 1);
+  }
+
+  {
+    // check that std::invoke is used
+    struct S { int i; };
+    S a[] = { S{1}, S{3}, S{2} };
+    std::same_as<S*> auto ret = std::ranges::find(a, 4, &S::i);
+    assert(ret == a + 3);
+  }
+
+  {
+    // count invocations of the projection
+    {
+      int a[] = {1, 2, 3, 4};
+      int projection_count = 0;
+      auto ret = std::ranges::find(a, a + 4, 2, [&](int i) { ++projection_count; return i; });
+      assert(ret == a + 1);
+      assert(*ret == 2);
+      assert(projection_count == 2);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      int projection_count = 0;
+      auto ret = std::ranges::find(a, 2, [&](int i) { ++projection_count; return i; });
+      assert(ret == a + 1);
+      assert(*ret == 2);
+      assert(projection_count == 2);
+    }
+  }
+
+  {
+    // check comparison order
+    {
+      OneWayComparable a[] = { OneWayComparable{true} };
+      auto ret = std::ranges::find(a, a + 1, OneWayComparable{false});
+      assert(ret == a);
+    }
+    {
+      OneWayComparable a[] = { OneWayComparable{true} };
+      auto ret = std::ranges::find(a, OneWayComparable{false});
+      assert(ret == a);
+    }
+  }
+
+  {
+    // check that the return type of `iter::operator*` doesn't change
+    {
+      NonConstComparableLValue a[] = { NonConstComparableLValue{} };
+      auto ret = std::ranges::find(a, a + 1, NonConstComparableLValue{});
+      assert(ret == a);
+    }
+    {
+      using It = std::move_iterator<NonConstComparableRValue*>;
+      NonConstComparableRValue a[] = { NonConstComparableRValue{} };
+      auto ret = std::ranges::find(It(a), It(a + 1), NonConstComparableRValue{});
+      assert(ret.base() == a);
+    }
+    {
+      NonConstComparableLValue a[] = { NonConstComparableLValue{} };
+      auto ret = std::ranges::find(a, NonConstComparableLValue{});
+      assert(ret == a);
+    }
+    {
+      using It = std::move_iterator<NonConstComparableRValue*>;
+      NonConstComparableRValue a[] = { NonConstComparableRValue{} };
+      auto range = std::ranges::subrange(It(a), It(a + 1));
+      auto ret = std::ranges::find(range, NonConstComparableRValue{});
+      assert(ret.base() == a);
+    }
+  }
+
+  {
+    // check that an empty range works
+    {
+      std::array<int ,0> a = {};
+      auto ret = std::ranges::find(a.begin(), a.end(), 1);
+      assert(ret == a.begin());
+    }
+    {
+      std::array<int, 0> a = {};
+      auto ret = std::ranges::find(a, 1);
+      assert(ret == a.begin());
+    }
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/algorithms/alg.nonmodifying/alg.find/ranges.find_if.pass.cpp

@@ -0,0 +1,235 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// template<input_iterator I, sentinel_for<I> S, class Proj = identity,
+//          indirect_unary_predicate<projected<I, Proj>> Pred>
+//   constexpr I ranges::find_if(I first, S last, Pred pred, Proj proj = {});
+// template<input_range R, class Proj = identity,
+//          indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
+//   constexpr borrowed_iterator_t<R>
+//     ranges::find_if(R&& r, Pred pred, Proj proj = {});
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+struct Predicate {
+  bool operator()(int);
+};
+
+template <class It, class Sent = It>
+concept HasFindIfIt = requires(It it, Sent sent) { std::ranges::find_if(it, sent, Predicate{}); };
+static_assert(HasFindIfIt<int*>);
+static_assert(!HasFindIfIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasFindIfIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasFindIfIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasFindIfIt<cpp20_input_iterator<int*>, SentinelForNotSemiregular>);
+static_assert(!HasFindIfIt<cpp20_input_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+
+static_assert(!HasFindIfIt<int*, int>);
+static_assert(!HasFindIfIt<int, int*>);
+
+template <class Pred>
+concept HasFindIfPred = requires(int* it, Pred pred) {std::ranges::find_if(it, it, pred); };
+
+static_assert(!HasFindIfPred<IndirectUnaryPredicateNotCopyConstructible>);
+static_assert(!HasFindIfPred<IndirectUnaryPredicateNotPredicate>);
+
+template <class R>
+concept HasFindIfR = requires(R r) { std::ranges::find_if(r, Predicate{}); };
+static_assert(HasFindIfR<std::array<int, 0>>);
+static_assert(!HasFindIfR<int>);
+static_assert(!HasFindIfR<InputRangeNotDerivedFrom>);
+static_assert(!HasFindIfR<InputRangeNotIndirectlyReadable>);
+static_assert(!HasFindIfR<InputRangeNotInputOrOutputIterator>);
+static_assert(!HasFindIfR<InputRangeNotSentinelSemiregular>);
+static_assert(!HasFindIfR<InputRangeNotSentinelEqualityComparableWith>);
+
+template <class It, class Sent = It>
+constexpr void test_iterators() {
+  {
+    int a[] = {1, 2, 3, 4};
+    std::same_as<It> auto ret = std::ranges::find_if(It(a), Sent(It(a + 4)), [](int x) mutable { return x == 4; });
+    assert(base(ret) == a + 3);
+    assert(*ret == 4);
+  }
+  {
+    int a[] = {1, 2, 3, 4};
+    auto range = std::ranges::subrange(It(a), Sent(It(a + 4)));
+    std::same_as<It> auto ret = std::ranges::find_if(range, [](int x) mutable { return x == 4; });
+    assert(base(ret) == a + 3);
+    assert(*ret == 4);
+  }
+}
+
+struct NonConstComparable {
+  friend constexpr bool operator==(const NonConstComparable&, const NonConstComparable&) { return false; }
+  friend constexpr bool operator==(NonConstComparable&, NonConstComparable&) { return false; }
+  friend constexpr bool operator==(const NonConstComparable&, NonConstComparable&) { return false; }
+  friend constexpr bool operator==(NonConstComparable&, const NonConstComparable&) { return true; }
+};
+
+constexpr bool test() {
+  test_iterators<int*>();
+  test_iterators<const int*>();
+  test_iterators<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>();
+  test_iterators<bidirectional_iterator<int*>>();
+  test_iterators<forward_iterator<int*>>();
+  test_iterators<random_access_iterator<int*>>();
+  test_iterators<contiguous_iterator<int*>>();
+
+  {
+    // check that projections are used properly and that they are called with the iterator directly
+    {
+      int a[] = {1, 2, 3, 4};
+      auto ret = std::ranges::find_if(a, a + 4, [&](int* i) { return i == a + 3; }, [](int& i) { return &i; });
+      assert(ret == a + 3);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      auto ret = std::ranges::find_if(a, [&](int* i) { return i == a + 3; }, [](int& i) { return &i; });
+      assert(ret == a + 3);
+    }
+  }
+
+  {
+    // check that the first element is returned
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::find_if(a, [](int i){ return i == 0; }, &S::comp);
+      assert(ret == a);
+      assert(ret->comp == 0);
+      assert(ret->other == 0);
+    }
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::find_if(a, a + 3, [](int i) { return i == 0; }, &S::comp);
+      assert(ret == a);
+      assert(ret->comp == 0);
+      assert(ret->other == 0);
+    }
+  }
+
+  {
+    // check that end + 1 iterator is returned with no match
+    {
+      int a[] = {1, 1, 1};
+      auto ret = std::ranges::find_if(a, a + 3, [](int) { return false; });
+      assert(ret == a + 3);
+    }
+    {
+      int a[] = {1, 1, 1};
+      auto ret = std::ranges::find_if(a, [](int){ return false; });
+      assert(ret == a + 3);
+    }
+  }
+
+  {
+    // check that ranges::dangling is returned
+    [[maybe_unused]] std::same_as<std::ranges::dangling> auto ret =
+      std::ranges::find_if(std::array{1, 2}, [](int){ return false; });
+  }
+
+  {
+    // check that an iterator is returned with a borrowing range
+    int a[] = {1, 2, 3, 4};
+    std::same_as<int*> auto ret = std::ranges::find_if(std::views::all(a), [](int){ return true; });
+    assert(ret == a);
+    assert(*ret == 1);
+  }
+
+  {
+    // check that std::invoke is used
+    struct S { int i; };
+    S a[] = { S{1}, S{3}, S{2} };
+    std::same_as<S*> auto ret = std::ranges::find_if(a, [](int) { return false; }, &S::i);
+    assert(ret == a + 3);
+  }
+
+  {
+    // count projection and predicate invocation count
+    {
+      int a[] = {1, 2, 3, 4};
+      int predicate_count = 0;
+      int projection_count = 0;
+      auto ret = std::ranges::find_if(a, a + 4,
+                                      [&](int i) { ++predicate_count; return i == 2; },
+                                      [&](int i) { ++projection_count; return i; });
+      assert(ret == a + 1);
+      assert(*ret == 2);
+      assert(predicate_count == 2);
+      assert(projection_count == 2);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      int predicate_count = 0;
+      int projection_count = 0;
+      auto ret = std::ranges::find_if(a,
+                                      [&](int i) { ++predicate_count; return i == 2; },
+                                      [&](int i) { ++projection_count; return i; });
+      assert(ret == a + 1);
+      assert(*ret == 2);
+      assert(predicate_count == 2);
+      assert(projection_count == 2);
+    }
+  }
+
+  {
+    // check that the return type of `iter::operator*` doesn't change
+    {
+      NonConstComparable a[] = { NonConstComparable{} };
+      auto ret = std::ranges::find_if(a, a + 1, [](auto&& e) { return e == NonConstComparable{}; });
+      assert(ret == a);
+    }
+    {
+      NonConstComparable a[] = { NonConstComparable{} };
+      auto ret = std::ranges::find_if(a, [](auto&& e) { return e == NonConstComparable{}; });
+      assert(ret == a);
+    }
+  }
+
+  {
+    // check that an empty range works
+    {
+      std::array<int ,0> a = {};
+      auto ret = std::ranges::find_if(a.begin(), a.end(), [](int) { return true; });
+      assert(ret == a.begin());
+    }
+    {
+      std::array<int, 0> a = {};
+      auto ret = std::ranges::find_if(a, [](int) { return true; });
+      assert(ret == a.begin());
+    }
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/algorithms/alg.nonmodifying/alg.find/ranges.find_if_not.pass.cpp

@@ -0,0 +1,229 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// template<input_iterator I, sentinel_for<I> S, class Proj = identity,
+//          indirect_unary_predicate<projected<I, Proj>> Pred>
+//   constexpr I ranges::find_if_not(I first, S last, Pred pred, Proj proj = {});
+// template<input_range R, class Proj = identity,
+//          indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
+//   constexpr borrowed_iterator_t<R>
+//     ranges::find_if_not(R&& r, Pred pred, Proj proj = {});
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+struct Predicate {
+  bool operator()(int);
+};
+
+template <class It, class Sent = It>
+concept HasFindIfNotIt = requires(It it, Sent sent) { std::ranges::find_if_not(it, sent, Predicate{}); };
+static_assert(HasFindIfNotIt<int*>);
+static_assert(!HasFindIfNotIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasFindIfNotIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasFindIfNotIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasFindIfNotIt<cpp20_input_iterator<int*>, SentinelForNotSemiregular>);
+static_assert(!HasFindIfNotIt<cpp20_input_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+
+static_assert(!HasFindIfNotIt<int*, int>);
+static_assert(!HasFindIfNotIt<int, int*>);
+
+template <class Pred>
+concept HasFindIfNotPred = requires(int* it, Pred pred) {std::ranges::find_if_not(it, it, pred); };
+
+static_assert(!HasFindIfNotPred<IndirectUnaryPredicateNotCopyConstructible>);
+static_assert(!HasFindIfNotPred<IndirectUnaryPredicateNotPredicate>);
+
+template <class R>
+concept HasFindIfNotR = requires(R r) { std::ranges::find_if_not(r, Predicate{}); };
+static_assert(HasFindIfNotR<std::array<int, 0>>);
+static_assert(!HasFindIfNotR<int>);
+static_assert(!HasFindIfNotR<InputRangeNotDerivedFrom>);
+static_assert(!HasFindIfNotR<InputRangeNotIndirectlyReadable>);
+static_assert(!HasFindIfNotR<InputRangeNotInputOrOutputIterator>);
+static_assert(!HasFindIfNotR<InputRangeNotSentinelSemiregular>);
+static_assert(!HasFindIfNotR<InputRangeNotSentinelEqualityComparableWith>);
+
+template <class It, class Sent = It>
+constexpr void test_iterators() {
+  {
+    int a[] = {1, 2, 3, 4};
+    std::same_as<It> auto ret = std::ranges::find_if_not(It(a), Sent(It(a + 4)), [c = 0](int) mutable { return c++ <= 2; });
+    assert(base(ret) == a + 3);
+    assert(*ret == 4);
+  }
+  {
+    int a[] = {1, 2, 3, 4};
+    auto range = std::ranges::subrange(It(a), Sent(It(a + 4)));
+    std::same_as<It> auto ret = std::ranges::find_if_not(range, [c = 0](int) mutable { return c++ <= 2; });
+    assert(base(ret) == a + 3);
+    assert(*ret == 4);
+  }
+}
+
+struct NonConstComparableLValue {
+  friend constexpr bool operator==(const NonConstComparableLValue&, const NonConstComparableLValue&) { return false; }
+  friend constexpr bool operator==(NonConstComparableLValue&, NonConstComparableLValue&) { return false; }
+  friend constexpr bool operator==(const NonConstComparableLValue&, NonConstComparableLValue&) { return false; }
+  friend constexpr bool operator==(NonConstComparableLValue&, const NonConstComparableLValue&) { return true; }
+};
+
+constexpr bool test() {
+  test_iterators<int*>();
+  test_iterators<const int*>();
+  test_iterators<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>();
+  test_iterators<bidirectional_iterator<int*>>();
+  test_iterators<forward_iterator<int*>>();
+  test_iterators<random_access_iterator<int*>>();
+  test_iterators<contiguous_iterator<int*>>();
+
+  { // check that projections are used properly and that they are called with the iterator directly
+    {
+      int a[] = {1, 2, 3, 4};
+      auto ret = std::ranges::find_if_not(a, a + 4, [&](int* i) { return i != a + 3; }, [](int& i) { return &i; });
+      assert(ret == a + 3);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      auto ret = std::ranges::find_if_not(a, [&](int* i) { return i != a + 3; }, [](int& i) { return &i; });
+      assert(ret == a + 3);
+    }
+  }
+
+  {
+    // check that the first element is returned
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::find_if_not(a, [](int i){ return i != 0; }, &S::comp);
+      assert(ret == a);
+      assert(ret->comp == 0);
+      assert(ret->other == 0);
+    }
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::find_if_not(a, a + 3, [](int i) { return i != 0; }, &S::comp);
+      assert(ret == a);
+      assert(ret->comp == 0);
+      assert(ret->other == 0);
+    }
+  }
+
+  {
+    // check that end + 1 iterator is returned with no match
+    {
+      int a[] = {1, 1, 1};
+      auto ret = std::ranges::find_if(a, a + 3, [](int) { return false; });
+      assert(ret == a + 3);
+    }
+    {
+      int a[] = {1, 1, 1};
+      auto ret = std::ranges::find_if(a, [](int){ return false; });
+      assert(ret == a + 3);
+    }
+  }
+
+  { // check that ranges::dangling is returned
+    [[maybe_unused]] std::same_as<std::ranges::dangling> auto ret =
+      std::ranges::find_if_not(std::array{1, 2}, [](int){ return true; });
+  }
+
+  { // check that an iterator is returned with a borrowing range
+    int a[] = {1, 2, 3, 4};
+    std::same_as<int*> auto ret = std::ranges::find_if_not(std::views::all(a), [](int){ return false; });
+    assert(ret == a);
+    assert(*ret == 1);
+  }
+
+  { // check that std::invoke is used
+    struct S { int i; };
+    S a[] = { S{1}, S{3}, S{2} };
+    std::same_as<S*> auto ret = std::ranges::find_if_not(a, [](int) { return true; }, &S::i);
+    assert(ret == a + 3);
+  }
+
+  { // count projection and predicate invocation count
+    {
+      int a[] = {1, 2, 3, 4};
+      int predicate_count = 0;
+      int projection_count = 0;
+      auto ret = std::ranges::find_if_not(a, a + 4,
+                                      [&](int i) { ++predicate_count; return i != 2; },
+                                      [&](int i) { ++projection_count; return i; });
+      assert(ret == a + 1);
+      assert(*ret == 2);
+      assert(predicate_count == 2);
+      assert(projection_count == 2);
+    }
+    {
+      int a[] = {1, 2, 3, 4};
+      int predicate_count = 0;
+      int projection_count = 0;
+      auto ret = std::ranges::find_if_not(a,
+                                      [&](int i) { ++predicate_count; return i != 2; },
+                                      [&](int i) { ++projection_count; return i; });
+      assert(ret == a + 1);
+      assert(*ret == 2);
+      assert(predicate_count == 2);
+      assert(projection_count == 2);
+    }
+  }
+
+  { // check that the return type of `iter::operator*` doesn't change
+    {
+      NonConstComparableLValue a[] = { NonConstComparableLValue{} };
+      auto ret = std::ranges::find_if_not(a, a + 1, [](auto&& e) { return e != NonConstComparableLValue{}; });
+      assert(ret == a);
+    }
+    {
+      NonConstComparableLValue a[] = { NonConstComparableLValue{} };
+      auto ret = std::ranges::find_if_not(a, [](auto&& e) { return e != NonConstComparableLValue{}; });
+      assert(ret == a);
+    }
+  }
+
+  {
+    // check that an empty range works
+    {
+      std::array<int ,0> a = {};
+      auto ret = std::ranges::find_if_not(a.begin(), a.end(), [](int) { return true; });
+      assert(ret == a.begin());
+    }
+    {
+      std::array<int, 0> a = {};
+      auto ret = std::ranges::find_if_not(a, [](int) { return true; });
+      assert(ret == a.begin());
+    }
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp

@@ -54,7 +54,7 @@ constexpr bool test(CPO& o, Args&&...) {
 
 int *p;
 int a[10];
-//auto odd = [](int x) { return x % 2 != 0; };
+auto odd = [](int x) { return x % 2 != 0; };
 //auto triple = [](int x) { return 3*x; };
 //auto plus = [](int x, int y) { return x == y; };
 //std::mt19937 g;
@@ -77,11 +77,11 @@ int a[10];
 //static_assert(test(std::ranges::equal_range, a, 42));
 //static_assert(test(std::ranges::fill, a, 42));
 //static_assert(test(std::ranges::fill_n, a, 10, 42));
-//static_assert(test(std::ranges::find, a, 42));
+static_assert(test(std::ranges::find, a, 42));
 //static_assert(test(std::ranges::find_end, a, a));
 //static_assert(test(std::ranges::find_first_of, a, a));
-//static_assert(test(std::ranges::find_if, a, odd));
-//static_assert(test(std::ranges::find_if_not, a, odd));
+static_assert(test(std::ranges::find_if, a, odd));
+static_assert(test(std::ranges::find_if_not, a, odd));
 //static_assert(test(std::ranges::for_each, a, odd));
 //static_assert(test(std::ranges::for_each_n, a, 10, odd));
 //static_assert(test(std::ranges::generate, a, 42));

libcxx/test/support/almost_satisfies_types.h

@@ -0,0 +1,131 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 ALMOST_SATISFIES_TYPES_H
+#define ALMOST_SATISFIES_TYPES_H
+
+#include <iterator>
+#include <ranges>
+
+#include "test_iterators.h"
+
+template <class T, class U = sentinel_wrapper<T>>
+class UncheckedRange {
+public:
+  T begin();
+  U end();
+};
+
+static_assert(std::ranges::contiguous_range<UncheckedRange<int*, int*>>);
+
+// almost an input_iterator
+class InputIteratorNotDerivedFrom {
+public:
+  using difference_type = long;
+  using value_type = int;
+  using iterator_category = void;
+
+  InputIteratorNotDerivedFrom& operator++();
+  void operator++(int);
+  const int& operator*() const;
+};
+
+using InputRangeNotDerivedFrom = UncheckedRange<InputIteratorNotDerivedFrom>;
+
+static_assert(std::input_or_output_iterator<InputIteratorNotDerivedFrom>);
+static_assert(std::indirectly_readable<InputIteratorNotDerivedFrom>);
+static_assert(!std::input_iterator<InputIteratorNotDerivedFrom>);
+static_assert(!std::ranges::input_range<InputRangeNotDerivedFrom>);
+
+class InputIteratorNotIndirectlyReadable {
+public:
+  using difference_type = long;
+  using iterator_category = std::input_iterator_tag;
+
+  InputIteratorNotIndirectlyReadable& operator++();
+  void operator++(int);
+  const int& operator*() const;
+};
+
+using InputRangeNotIndirectlyReadable = UncheckedRange<InputIteratorNotIndirectlyReadable>;
+
+static_assert(std::input_or_output_iterator<InputIteratorNotIndirectlyReadable>);
+static_assert(!std::indirectly_readable<InputIteratorNotIndirectlyReadable>);
+static_assert(!std::input_iterator<InputIteratorNotIndirectlyReadable>);
+static_assert(!std::ranges::input_range<InputIteratorNotIndirectlyReadable>);
+
+class InputIteratorNotInputOrOutputIterator {
+public:
+  using difference_type = long;
+  using value_type = int;
+  using iterator_category = std::input_iterator_tag;
+
+  int& operator++();
+  void operator++(int);
+  const int& operator*() const;
+};
+
+using InputRangeNotInputOrOutputIterator = UncheckedRange<InputIteratorNotInputOrOutputIterator>;
+
+static_assert(!std::input_or_output_iterator<InputIteratorNotInputOrOutputIterator>);
+static_assert(std::indirectly_readable<InputIteratorNotInputOrOutputIterator>);
+static_assert(!std::input_iterator<InputIteratorNotInputOrOutputIterator>);
+static_assert(!std::ranges::input_range<InputRangeNotInputOrOutputIterator>);
+
+// almost an indirect_unary_predicate
+class IndirectUnaryPredicateNotCopyConstructible {
+public:
+  IndirectUnaryPredicateNotCopyConstructible(const IndirectUnaryPredicateNotCopyConstructible&) = delete;
+  bool operator()(int) const;
+};
+
+static_assert(std::predicate<IndirectUnaryPredicateNotCopyConstructible, int&>);
+static_assert(!std::indirect_unary_predicate<IndirectUnaryPredicateNotCopyConstructible, int*>);
+
+class IndirectUnaryPredicateNotPredicate {
+public:
+  bool operator()(int&&) const;
+};
+
+static_assert(!std::predicate<IndirectUnaryPredicateNotPredicate, int&>);
+static_assert(!std::indirect_unary_predicate<IndirectUnaryPredicateNotPredicate, int*>);
+
+// almost a sentinel_for cpp20_input_iterator
+class SentinelForNotSemiregular {
+public:
+  SentinelForNotSemiregular() = delete;
+  using difference_type = long;
+  SentinelForNotSemiregular& operator++();
+  void operator++(int);
+  const int& operator*() const;
+  friend bool operator==(const SentinelForNotSemiregular&, const cpp20_input_iterator<int*>&);
+};
+
+using InputRangeNotSentinelSemiregular = UncheckedRange<cpp20_input_iterator<int*>, SentinelForNotSemiregular>;
+
+static_assert(std::input_or_output_iterator<SentinelForNotSemiregular>);
+static_assert(!std::semiregular<SentinelForNotSemiregular>);
+static_assert(!std::sentinel_for<SentinelForNotSemiregular, cpp20_input_iterator<int*>>);
+
+// almost a sentinel_for cpp20_input_iterator
+class SentinelForNotWeaklyEqualityComparableWith {
+public:
+  using difference_type = long;
+  SentinelForNotWeaklyEqualityComparableWith& operator++();
+  void operator++(int);
+  const int& operator*() const;
+};
+
+using InputRangeNotSentinelEqualityComparableWith =
+  UncheckedRange<cpp20_input_iterator<int*>, SentinelForNotWeaklyEqualityComparableWith>;
+
+static_assert(std::input_or_output_iterator<SentinelForNotWeaklyEqualityComparableWith>);
+static_assert(std::semiregular<SentinelForNotWeaklyEqualityComparableWith>);
+static_assert(!std::sentinel_for<SentinelForNotWeaklyEqualityComparableWith, cpp20_input_iterator<int*>>);
+
+#endif // ALMOST_SATISFIES_TYPES_H