[libc++][ranges] Implement ranges::minmax and ranges::minmax_element

Reviewed By: var-const, #libc, ldionne

Spies: sstefan1, ldionne, BRevzin, libcxx-commits, mgorny

Differential Revision: https://reviews.llvm.org/D120637

libcxx/benchmarks/algorithms.bench.cpp

@@ -352,6 +352,21 @@ struct PopHeap {
   };
 };
 
+template <class ValueType, class Order>
+struct MinMaxElement {
+  size_t Quantity;
+
+  void run(benchmark::State& state) const {
+    runOpOnCopies<ValueType>(state, Quantity, Order(), BatchSize::CountElements, [](auto& Copy) {
+      benchmark::DoNotOptimize(std::minmax_element(Copy.begin(), Copy.end()));
+    });
+  }
+
+  std::string name() const {
+    return "BM_MinMaxElement" + ValueType::name() + Order::name() + "_" + std::to_string(Quantity);
+  }
+};
+
 } // namespace
 
 int main(int argc, char** argv) {
@@ -376,5 +391,6 @@ int main(int argc, char** argv) {
       Quantities);
   makeCartesianProductBenchmark<PushHeap, AllValueTypes, AllOrders>(Quantities);
   makeCartesianProductBenchmark<PopHeap, AllValueTypes>(Quantities);
+  makeCartesianProductBenchmark<MinMaxElement, AllValueTypes, AllOrders>(Quantities);
   benchmark::RunSpecifiedBenchmarks();
 }

libcxx/docs/Status/Cxx20Issues.csv

@@ -139,7 +139,7 @@
 "`3144 <https://wg21.link/LWG3144>`__","``span``\  does not have a ``const_pointer``\  typedef","Kona","|Complete|",""
 "`3173 <https://wg21.link/LWG3173>`__","Enable CTAD for ``ref-view``\ ","Kona","","","|ranges|"
 "`3179 <https://wg21.link/LWG3179>`__","``subrange``\  should always model ``Range``\ ","Kona","","","|ranges|"
-"`3180 <https://wg21.link/LWG3180>`__","Inconsistently named return type for ``ranges::minmax_element``\ ","Kona","","","|ranges|"
+"`3180 <https://wg21.link/LWG3180>`__","Inconsistently named return type for ``ranges::minmax_element``\ ","Kona","|Complete|","15.0","|ranges|"
 "`3182 <https://wg21.link/LWG3182>`__","Specification of ``Same``\  could be clearer","Kona","",""
 "","","","",""
 "`2899 <https://wg21.link/LWG2899>`__","``is_(nothrow_)move_constructible``\  and ``tuple``\ , ``optional``\  and ``unique_ptr``\ ","Cologne","",""

libcxx/docs/Status/RangesAlgorithms.csv

@@ -17,10 +17,10 @@ Search,equal_range,Christopher Di Bella,n/a,Not started
 Search,binary_search,Christopher Di Bella,n/a,Not started
 Search,min,Nikolas Klauser,`D119589 <https://llvm.org/D119589>`_,✅
 Search,max,Nikolas Klauser,`D122002 <https://llvm.org/D122002>`_,✅
-Search,minmax,Not assigned,n/a,Not started
+Search,minmax,Nikolas Klauser,`D120637 <https://llvm.org/D120637>`_,✅
 Search,min_element,Nikolas Klauser,`D117025 <https://llvm.org/D117025>`_,✅
 Search,max_element,Nikolas Klauser,`D117523 <https://llvm.org/D117523>`_,✅
-Search,minmax_element,Not assigned,n/a,Not started
+Search,minmax_element,Nikolas Klauser,`D120637 <https://llvm.org/D120637>`_,✅
 Search,count,Nikolas Klauser, `D121523 <https://llvm.org/D121523>`_,✅
 Search,count_if,Nikolas Klauser, `D121523 <https://llvm.org/D121523>`_,✅
 Search,search,Not assigned,n/a,Not started

libcxx/include/CMakeLists.txt

@@ -75,6 +75,8 @@ set(files
   __algorithm/ranges_max_element.h
   __algorithm/ranges_min.h
   __algorithm/ranges_min_element.h
+  __algorithm/ranges_minmax.h
+  __algorithm/ranges_minmax_element.h
   __algorithm/ranges_mismatch.h
   __algorithm/ranges_swap_ranges.h
   __algorithm/ranges_transform.h

libcxx/include/__algorithm/minmax.h

@@ -10,7 +10,10 @@
 #define _LIBCPP___ALGORITHM_MINMAX_H
 
 #include <__algorithm/comp.h>
+#include <__algorithm/minmax_element.h>
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/is_callable.h>
 #include <__utility/pair.h>
 #include <initializer_list>
 
@@ -36,47 +39,18 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 pair<const _Tp&, const _Tp&>
 minmax(const _Tp& __a, const _Tp& __b)
 {
-    return _VSTD::minmax(__a, __b, __less<_Tp>());
+    return std::minmax(__a, __b, __less<_Tp>());
 }
 
 #ifndef _LIBCPP_CXX03_LANG
 
 template<class _Tp, class _Compare>
-_LIBCPP_NODISCARD_EXT inline
-_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-pair<_Tp, _Tp>
-minmax(initializer_list<_Tp> __t, _Compare __comp)
-{
-    typedef typename initializer_list<_Tp>::const_iterator _Iter;
-    _Iter __first = __t.begin();
-    _Iter __last  = __t.end();
-    pair<_Tp, _Tp> __result(*__first, *__first);
-
-    ++__first;
-    if (__t.size() % 2 == 0)
-    {
-        if (__comp(*__first,  __result.first))
-            __result.first  = *__first;
-        else
-            __result.second = *__first;
-        ++__first;
-    }
-
-    while (__first != __last)
-    {
-        _Tp __prev = *__first++;
-        if (__comp(*__first, __prev)) {
-            if ( __comp(*__first, __result.first)) __result.first  = *__first;
-            if (!__comp(__prev, __result.second))  __result.second = __prev;
-            }
-        else {
-            if ( __comp(__prev, __result.first))    __result.first  = __prev;
-            if (!__comp(*__first, __result.second)) __result.second = *__first;
-            }
-
-        __first++;
-    }
-    return __result;
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
+pair<_Tp, _Tp> minmax(initializer_list<_Tp> __t, _Compare __comp) {
+    static_assert(__is_callable<_Compare, _Tp, _Tp>::value, "The comparator has to be callable");
+    __identity __proj;
+    auto __ret = std::__minmax_element_impl(__t.begin(), __t.end(), __comp, __proj);
+    return pair<_Tp, _Tp>(*__ret.first, *__ret.second);
 }
 
 template<class _Tp>
@@ -85,7 +59,7 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 pair<_Tp, _Tp>
 minmax(initializer_list<_Tp> __t)
 {
-    return _VSTD::minmax(__t, __less<_Tp>());
+    return std::minmax(__t, __less<_Tp>());
 }
 
 #endif // _LIBCPP_CXX03_LANG

libcxx/include/__algorithm/minmax_element.h

@@ -11,8 +11,10 @@
 
 #include <__algorithm/comp.h>
 #include <__config>
+#include <__functional/identity.h>
 #include <__iterator/iterator_traits.h>
 #include <__utility/pair.h>
+#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -20,64 +22,78 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _ForwardIterator, class _Compare>
-_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX11
-pair<_ForwardIterator, _ForwardIterator>
-minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
-{
-  static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
-        "std::minmax_element requires a ForwardIterator");
-  pair<_ForwardIterator, _ForwardIterator> __result(__first, __first);
-  if (__first != __last)
-  {
-      if (++__first != __last)
-      {
-          if (__comp(*__first, *__result.first))
-              __result.first = __first;
-          else
-              __result.second = __first;
-          while (++__first != __last)
-          {
-              _ForwardIterator __i = __first;
-              if (++__first == __last)
-              {
-                  if (__comp(*__i, *__result.first))
-                      __result.first = __i;
-                  else if (!__comp(*__i, *__result.second))
-                      __result.second = __i;
-                  break;
-              }
-              else
-              {
-                  if (__comp(*__first, *__i))
-                  {
-                      if (__comp(*__first, *__result.first))
-                          __result.first = __first;
-                      if (!__comp(*__i, *__result.second))
-                          __result.second = __i;
-                  }
-                  else
-                  {
-                      if (__comp(*__i, *__result.first))
-                          __result.first = __i;
-                      if (!__comp(*__first, *__result.second))
-                          __result.second = __first;
-                  }
-              }
-          }
-      }
+template <class _Comp, class _Proj>
+class _MinmaxElementLessFunc {
+  _Comp& __comp;
+  _Proj& __proj;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
+  _MinmaxElementLessFunc(_Comp& __comp_, _Proj& __proj_) : __comp(__comp_), __proj(__proj_) {}
+
+  template <class _Iter>
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
+  bool operator()(_Iter& __it1, _Iter& __it2) {
+    return std::__invoke(__comp, std::__invoke(__proj, *__it1), std::__invoke(__proj, *__it2));
   }
+};
+
+template <class _Iter, class _Sent, class _Proj, class _Comp>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
+pair<_Iter, _Iter> __minmax_element_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
+  auto __less = _MinmaxElementLessFunc<_Comp, _Proj>(__comp, __proj);
+
+  pair<_Iter, _Iter> __result(__first, __first);
+  if (__first == __last || ++__first == __last)
+    return __result;
+
+  if (__less(__first, __result.first))
+    __result.first = __first;
+  else
+    __result.second = __first;
+
+  while (++__first != __last) {
+    _Iter __i = __first;
+    if (++__first == __last) {
+      if (__less(__i, __result.first))
+        __result.first = __i;
+      else if (!__less(__i, __result.second))
+        __result.second = __i;
+      return __result;
+    }
+
+    if (__less(__first, __i)) {
+      if (__less(__first, __result.first))
+        __result.first = __first;
+    if (!__less(__i, __result.second))
+      __result.second = __i;
+    } else {
+      if (__less(__i, __result.first))
+        __result.first = __i;
+      if (!__less(__first, __result.second))
+        __result.second = __first;
+    }
+  }
+
   return __result;
 }
 
-template <class _ForwardIterator>
-_LIBCPP_NODISCARD_EXT inline
-_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+template <class _ForwardIterator, class _Compare>
+_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX11
 pair<_ForwardIterator, _ForwardIterator>
-minmax_element(_ForwardIterator __first, _ForwardIterator __last)
-{
-    return _VSTD::minmax_element(__first, __last,
-              __less<typename iterator_traits<_ForwardIterator>::value_type>());
+minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) {
+  static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
+                "std::minmax_element requires a ForwardIterator");
+  static_assert(__is_callable<_Compare, decltype(*__first), decltype(*__first)>::value,
+                "The comparator has to be callable");
+  auto __proj = __identity();
+  return std::__minmax_element_impl(__first, __last, __comp, __proj);
+}
+
+template <class _ForwardIterator>
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
+pair<_ForwardIterator, _ForwardIterator> minmax_element(_ForwardIterator __first, _ForwardIterator __last) {
+    return std::minmax_element(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
 }
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/__algorithm/ranges_minmax.h

@@ -0,0 +1,128 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_MINMAX_H
+#define _LIBCPP___ALGORITHM_RANGES_MINMAX_H
+
+#include <__algorithm/min_max_result.h>
+#include <__algorithm/minmax_element.h>
+#include <__assert>
+#include <__concepts/copyable.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 <__utility/forward.h>
+#include <__utility/move.h>
+#include <initializer_list>
+
+#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 _T1>
+using minmax_result = min_max_result<_T1>;
+
+namespace __minmax {
+struct __fn {
+  template <class _Type, class _Proj = identity,
+            indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
+  _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<const _Type&>
+  operator()(const _Type& __a, const _Type& __b, _Comp __comp = {}, _Proj __proj = {}) const {
+    if (std::invoke(__comp, std::invoke(__proj, __b), std::invoke(__proj, __a)))
+      return {__b, __a};
+    return {__a, __b};
+  }
+
+  template <copyable _Type, class _Proj = identity,
+            indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  ranges::minmax_result<_Type> operator()(initializer_list<_Type> __il, _Comp __comp = {}, _Proj __proj = {}) const {
+    _LIBCPP_ASSERT(__il.begin() != __il.end(), "initializer_list has to contain at least one element");
+    auto __iters = std::__minmax_element_impl(__il.begin(), __il.end(), __comp, __proj);
+    return ranges::minmax_result<_Type> { *__iters.first, *__iters.second };
+  }
+
+  template <input_range _Range, class _Proj = identity,
+            indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
+    requires indirectly_copyable_storable<iterator_t<_Range>, range_value_t<_Range>*>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  ranges::minmax_result<range_value_t<_Range>> operator()(_Range&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
+    auto __first = ranges::begin(__r);
+    auto __last = ranges::end(__r);
+    using _ValueT = range_value_t<_Range>;
+
+    _LIBCPP_ASSERT(__first != __last, "range has to contain at least one element");
+
+    if constexpr (forward_range<_Range>) {
+      auto __result = std::__minmax_element_impl(__first, __last, __comp, __proj);
+      return {*__result.first, *__result.second};
+    } else {
+      // input_iterators can't be copied, so the implementation for input_iterators has to store
+      // the values instead of a pointer to the correct values
+      auto __less = [&](auto&& __a, auto&& __b) -> bool {
+        return std::invoke(__comp, std::invoke(__proj, std::forward<decltype(__a)>(__a)),
+                                   std::invoke(__proj, std::forward<decltype(__b)>(__b)));
+      };
+
+      ranges::minmax_result<_ValueT> __result = {*__first, __result.min};
+      if (__first == __last || ++__first == __last)
+        return __result;
+
+      if (__less(*__first, __result.min))
+        __result.min = *__first;
+      else
+        __result.max = *__first;
+
+      while (++__first != __last) {
+        _ValueT __i = *__first;
+        if (++__first == __last) {
+          if (__less(__i, __result.min))
+            __result.min = __i;
+          else if (!__less(__i, __result.max))
+            __result.max = __i;
+          return __result;
+        }
+
+        if (__less(*__first, __i)) {
+          if (__less(*__first, __result.min))
+            __result.min = *__first;
+          if (!__less(__i, __result.max))
+            __result.max = std::move(__i);
+        } else {
+          if (__less(__i, __result.min))
+            __result.min = std::move(__i);
+          if (!__less(*__first, __result.max))
+            __result.max = *__first;
+        }
+      }
+      return __result;
+    }
+  }
+};
+} // namespace __minmax
+
+inline namespace __cpo {
+  inline constexpr auto minmax = __minmax::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // _LIBCPP___ALGORITHM_RANGES_MINMAX_H

libcxx/include/__algorithm/ranges_minmax_element.h

@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_MINMAX_ELEMENT_H
+#define _LIBCPP___ALGORITHM_RANGES_MINMAX_ELEMENT_H
+
+#include <__algorithm/min_max_result.h>
+#include <__algorithm/minmax_element.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>
+#include <__utility/pair.h>
+#include <type_traits>
+
+#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 _T1>
+using minmax_element_result = min_max_result<_T1>;
+
+namespace __minmax_element {
+struct __fn {
+  template <forward_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
+            indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  ranges::minmax_element_result<_Ip> operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
+    auto __ret = std::__minmax_element_impl(std::move(__first), std::move(__last), __comp, __proj);
+    return {__ret.first, __ret.second};
+  }
+
+  template <forward_range _Rp, class _Proj = identity,
+            indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  ranges::minmax_element_result<borrowed_iterator_t<_Rp>>
+  operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
+    auto __ret = std::__minmax_element_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
+    return {__ret.first, __ret.second};
+  }
+};
+} // namespace __minmax_element
+
+inline namespace __cpo {
+  inline constexpr auto minmax_element = __minmax_element::__fn{};
+} // namespace __cpo
+
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // _LIBCPP___ALGORITHM_RANGES_MINMAX_H

libcxx/include/__functional/identity.h

@@ -19,6 +19,15 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+struct __identity {
+  template <class _Tp>
+  _LIBCPP_NODISCARD _LIBCPP_CONSTEXPR _Tp&& operator()(_Tp&& __t) const _NOEXCEPT {
+    return std::forward<_Tp>(__t);
+  }
+
+  using is_transparent = void;
+};
+
 #if _LIBCPP_STD_VER > 17
 
 struct identity {

libcxx/include/algorithm

@@ -165,6 +165,32 @@ namespace ranges {
            indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
     constexpr range_difference_t<R>
       count_if(R&& r, Pred pred, Proj proj = {});                                   // since C++20
+
+  template<class T, class Proj = identity,
+           indirect_strict_weak_order<projected<const T*, Proj>> Comp = ranges::less>
+    constexpr ranges::minmax_result<const T&>
+      minmax(const T& a, const T& b, Comp comp = {}, Proj proj = {});                     // since C++20
+
+  template<copyable T, class Proj = identity,
+           indirect_strict_weak_order<projected<const T*, Proj>> Comp = ranges::less>
+    constexpr ranges::minmax_result<T>
+      minmax(initializer_list<T> r, Comp comp = {}, Proj proj = {});                      // since C++20
+
+  template<input_range R, class Proj = identity,
+           indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less>
+    requires indirectly_copyable_storable<iterator_t<R>, range_value_t<R>*>
+    constexpr ranges::minmax_result<range_value_t<R>>
+      minmax(R&& r, Comp comp = {}, Proj proj = {});                                      // since C++20
+
+  template<forward_iterator I, sentinel_for<I> S, class Proj = identity,
+           indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>
+    constexpr ranges::minmax_element_result<I>
+      minmax_element(I first, S last, Comp comp = {}, Proj proj = {});                    // since C++20
+
+  template<forward_range R, class Proj = identity,
+           indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less>
+    constexpr ranges::minmax_element_result<borrowed_iterator_t<R>>
+      minmax_element(R&& r, Comp comp = {}, Proj proj = {});                              // since C++20
 }
 
     constexpr bool     // constexpr in C++20
@@ -891,6 +917,8 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/ranges_max_element.h>
 #include <__algorithm/ranges_min.h>
 #include <__algorithm/ranges_min_element.h>
+#include <__algorithm/ranges_minmax.h>
+#include <__algorithm/ranges_minmax_element.h>
 #include <__algorithm/ranges_mismatch.h>
 #include <__algorithm/ranges_swap_ranges.h>
 #include <__algorithm/ranges_transform.h>

libcxx/include/module.modulemap

@@ -303,6 +303,8 @@ module std [system] {
       module ranges_max_element       { private header "__algorithm/ranges_max_element.h" }
       module ranges_min               { private header "__algorithm/ranges_min.h" }
       module ranges_min_element       { private header "__algorithm/ranges_min_element.h" }
+      module ranges_minmax            { private header "__algorithm/ranges_minmax.h" }
+      module ranges_minmax_element    { private header "__algorithm/ranges_minmax_element.h" }
       module ranges_mismatch          { private header "__algorithm/ranges_mismatch.h" }
       module ranges_swap_ranges       { private header "__algorithm/ranges_swap_ranges.h" }
       module ranges_transform         { private header "__algorithm/ranges_transform.h" }

libcxx/include/type_traits

@@ -416,7 +416,6 @@ namespace std
 }
 
 */
-
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__type_traits/integral_constant.h>
@@ -3568,6 +3567,15 @@ struct __invoke_of
 {
 };
 
+#else
+
+// Assume that it's a functor in C++03
+template <class _Func, class... _Args>
+_LIBCPP_HIDE_FROM_ABI
+decltype(std::declval<_Func>()(std::declval<_Args>()...)) __invoke(_Func&& __func, _Args&&... __args) {
+    return static_cast<_Func&&>(__func)(static_cast<_Args&&>(__args)...);
+}
+
 #endif // _LIBCPP_CXX03_LANG
 
 // result_of

libcxx/test/libcxx/algorithms/alg.sorting/assert.min.max.pass.cpp

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+// UNSUPPORTED: windows
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_ASSERTIONS=1
+
+#include <algorithm>
+#include <array>
+
+#include "check_assertion.h"
+
+int main(int, char**) {
+  std::initializer_list<int> init_list{};
+  TEST_LIBCPP_ASSERT_FAILURE(std::ranges::minmax(init_list),
+                             "initializer_list has to contain at least one element");
+
+  TEST_LIBCPP_ASSERT_FAILURE(std::ranges::minmax(std::array<int, 0>{}),
+                             "range has to contain at least one element");
+
+  return 0;
+}

libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp

@@ -86,7 +86,7 @@ constexpr bool all_the_algorithms()
     void **first2 = b;
     //void **mid2 = b+5;
     void **last2 = b+10;
-    //void *value = nullptr;
+    void *value = nullptr;
     //int count = 1;
 
     int copies = 0;
@@ -158,11 +158,11 @@ constexpr bool all_the_algorithms()
     //(void)std::ranges::min(a, Less(&copies)); assert(copies == 0);
     (void)std::ranges::min_element(first, last, Less(&copies)); assert(copies == 0);
     (void)std::ranges::min_element(a, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax(value, value, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax({ value, value }, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax(a, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax_element(first, last, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax_element(a, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax(value, value, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax({ value, value }, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax(a, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax_element(first, last, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax_element(a, Less(&copies)); assert(copies == 0);
     (void)std::ranges::mismatch(first, last, first2, last2, Equal(&copies)); assert(copies == 0);
     (void)std::ranges::mismatch(a, b, Equal(&copies)); assert(copies == 0);
     //(void)std::ranges::next_permutation(first, last, Less(&copies)); assert(copies == 0);

libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp

@@ -141,11 +141,11 @@ constexpr bool all_the_algorithms()
     //(void)std::ranges::min(a, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::min_element(first, last, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::min_element(a, Less(), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax(T(), T(), Less(), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax({ T(), T() }, Less(), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax(a, Less(), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax_element(first, last, Less(), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::minmax_element(a, Less(), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax(T(), T(), Less(), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax({ T(), T() }, Less(), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax(a, Less(), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax_element(first, last, Less(), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::minmax_element(a, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::mismatch(first, last, first2, last2, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::mismatch(a, b, Equal(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::next_permutation(first, last, Less(), Proj(&copies)); assert(copies == 0);

libcxx/test/libcxx/private_headers.verify.cpp

@@ -112,6 +112,8 @@ END-SCRIPT
 #include <__algorithm/ranges_max_element.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_max_element.h'}}
 #include <__algorithm/ranges_min.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_min.h'}}
 #include <__algorithm/ranges_min_element.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_min_element.h'}}
+#include <__algorithm/ranges_minmax.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_minmax.h'}}
+#include <__algorithm/ranges_minmax_element.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_minmax_element.h'}}
 #include <__algorithm/ranges_mismatch.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_mismatch.h'}}
 #include <__algorithm/ranges_swap_ranges.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_swap_ranges.h'}}
 #include <__algorithm/ranges_transform.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_transform.h'}}

libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax.pass.cpp

@@ -0,0 +1,351 @@
+//===----------------------------------------------------------------------===//
+//
+// 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<class T, class Proj = identity,
+//          indirect_strict_weak_order<projected<const T*, Proj>> Comp = ranges::less>
+//   constexpr ranges::minmax_result<const T&>
+//     ranges::minmax(const T& a, const T& b, Comp comp = {}, Proj proj = {});
+// template<copyable T, class Proj = identity,
+//          indirect_strict_weak_order<projected<const T*, Proj>> Comp = ranges::less>
+//   constexpr ranges::minmax_result<T>
+//     ranges::minmax(initializer_list<T> r, Comp comp = {}, Proj proj = {});
+// template<input_range R, class Proj = identity,
+//          indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less>
+//   requires indirectly_copyable_storable<iterator_t<R>, range_value_t<R>*>
+//   constexpr ranges::minmax_result<range_value_t<R>>
+//     ranges::minmax(R&& r, Comp comp = {}, Proj proj = {});
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+
+#include "test_iterators.h"
+
+template <class T>
+concept HasMinMax = requires { std::ranges::minmax(std::declval<T>()); };
+
+struct NoLessThanOp {};
+struct NotTotallyOrdered {
+  int i;
+  bool operator<(const NotTotallyOrdered& o) const { return i < o.i; }
+};
+struct MoveOnly {
+  MoveOnly(MoveOnly&&) = default;
+  MoveOnly& operator=(MoveOnly&&) = default;
+  MoveOnly(const MoveOnly&) = delete;
+};
+
+static_assert(!HasMinMax<int>);
+
+static_assert(HasMinMax<int (&)[10]>); // make sure HasMinMax works with an array
+static_assert(!HasMinMax<NoLessThanOp (&)[10]>);
+static_assert(!HasMinMax<NotTotallyOrdered (&)[10]>);
+static_assert(!HasMinMax<MoveOnly (&)[10]>);
+
+static_assert(HasMinMax<std::initializer_list<int>>); // make sure HasMinMax works with an initializer_list
+static_assert(!HasMinMax<std::initializer_list<NoLessThanOp>>);
+static_assert(!HasMinMax<std::initializer_list<NotTotallyOrdered>>);
+static_assert(!HasMinMax<std::initializer_list<MoveOnly>>);
+
+static_assert(std::is_same_v<std::ranges::minmax_result<int>, std::ranges::min_max_result<int>>);
+
+static_assert(std::is_same_v<decltype(std::ranges::minmax(1, 2)), std::ranges::minmax_result<const int&>>);
+
+constexpr void test_2_arguments() {
+  const int one = 1;
+  const int two = 2;
+  {
+    auto result = std::ranges::minmax(one, two);
+    assert(result.min == 1);
+    assert(result.max == 2);
+  }
+
+  {
+    auto result = std::ranges::minmax(two, one);
+    assert(result.min == 1);
+    assert(result.max == 2);
+  }
+
+  {
+    // test comparator
+    auto result = std::ranges::minmax(one, two, std::ranges::greater{});
+    assert(result.min == 2);
+    assert(result.max == 1);
+  }
+
+  {
+    // test projection
+    auto result = std::ranges::minmax(one, two, std::ranges::less{}, [](int i) { return i == 1 ? 10 : i; });
+    assert(result.min == 2);
+    assert(result.max == 1);
+  }
+
+  {
+    // test if std::invoke is used for the predicate
+    struct S {
+      int i;
+    };
+    S a[3] = {S{2}, S{1}, S{3}};
+    std::same_as<std::ranges::minmax_result<const S&>> auto ret = std::ranges::minmax(a[0], a[1], {}, &S::i);
+    assert(&ret.min == &a[1]);
+    assert(&ret.max == &a[0]);
+    assert(ret.min.i == 1);
+    assert(ret.max.i == 2);
+  }
+
+  {
+    // check that std::invoke is used for the comparator
+    struct S {
+      int i;
+      constexpr bool comp(S rhs) const { return i < rhs.i; }
+    };
+    S a[] = {{2}, {5}};
+    auto ret = std::ranges::minmax(a[0], a[1], &S::comp);
+    assert(ret.min.i == 2);
+    assert(ret.max.i == 5);
+  }
+
+  {
+    // make sure that {a, b} is returned if b is not less than a
+    auto r = std::ranges::minmax(one, two);
+    assert(&r.min == &one);
+    assert(&r.max == &two);
+  }
+}
+
+constexpr void test_initializer_list() {
+  {
+    // test projection
+    auto proj = [](int i) { return i == 5 ? -100 : i; };
+    auto ret = std::ranges::minmax({7, 6, 9, 3, 5, 1, 2, 4}, std::ranges::less{}, proj);
+    assert(ret.min == 5);
+    assert(ret.max == 9);
+  }
+
+  {
+    // test comparator
+    auto ret = std::ranges::minmax({7, 6, 9, 3, 5, 1, 2, 4}, std::ranges::greater{});
+    assert(ret.min == 9);
+    assert(ret.max == 1);
+  }
+
+  {
+    // check predicate and projection call counts
+    int compares = 0;
+    int projections = 0;
+    auto comparator = [&](int a, int b) {
+      ++compares;
+      return a < b;
+    };
+    auto projection = [&](int a) {
+      ++projections;
+      return a;
+    };
+    std::same_as<std::ranges::minmax_result<int>> auto ret = std::ranges::minmax({1, 2, 3}, comparator, projection);
+    assert(ret.min == 1);
+    assert(ret.max == 3);
+    assert(compares == 3);
+    assert(projections == 6);
+  }
+
+  {
+    // check that std::invoke is used for the predicate
+    struct S {
+      int i;
+    };
+    std::same_as<std::ranges::minmax_result<S>> auto ret = std::ranges::minmax({S{2}, S{1}, S{3}}, {}, &S::i);
+    assert(ret.min.i == 1);
+    assert(ret.max.i == 3);
+  }
+
+  {
+    // check that std::invoke is used for the comparator
+    struct S {
+      int i;
+      constexpr bool comp(S rhs) const { return i < rhs.i; }
+    };
+    auto ret = std::ranges::minmax({S {1}, S {2}, S {3}, S {4}}, &S::comp);
+    assert(ret.min.i == 1);
+    assert(ret.max.i == 4);
+  }
+
+  {
+    // check that a single element works
+    auto ret = std::ranges::minmax({ 1 });
+    assert(ret.min == 1);
+    assert(ret.max == 1);
+  }
+
+  {
+    // check in ascending order
+    auto ret = std::ranges::minmax({1, 2, 3});
+    assert(ret.min == 1);
+    assert(ret.max == 3);
+  }
+
+  {
+    // check in descending order
+    auto ret = std::ranges::minmax({3, 2, 1});
+    assert(ret.min == 1);
+    assert(ret.max == 3);
+  }
+}
+
+template <class Iter, class Sent = Iter>
+constexpr void test_range_types() {
+  {
+    // test projection
+    int a[] = {7, 6, 9, 3, 5, 1, 2, 4};
+    auto proj = [](int& i) { return i == 5 ? -100 : i; };
+    auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 8)));
+    auto ret = std::ranges::minmax(range, std::ranges::less{}, proj);
+    assert(ret.min == 5);
+    assert(ret.max == 9);
+  }
+
+  {
+    // test comparator
+    int a[] = {7, 6, 9, 3, 5, 1, 2, 4};
+    auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 8)));
+    auto ret = std::ranges::minmax(range, std::ranges::greater{});
+    assert(ret.min == 9);
+    assert(ret.max == 1);
+  }
+
+  {
+    // check that complexity requirements are met
+    int compares = 0;
+    int projections = 0;
+    auto comparator = [&](int x, int y) {
+      ++compares;
+      return x < y;
+    };
+    auto projection = [&](int x) {
+      ++projections;
+      return x;
+    };
+    int a[] = {1, 2, 3};
+    auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 3)));
+    std::same_as<std::ranges::minmax_result<int>> auto ret = std::ranges::minmax(range, comparator, projection);
+    assert(ret.min == 1);
+    assert(ret.max == 3);
+    assert(compares == 3);
+    assert(projections == 6);
+  }
+
+  {
+    // check that a single element works
+    int a[] = { 1 };
+    auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 1)));
+    auto ret = std::ranges::minmax(range);
+    assert(ret.min == 1);
+    assert(ret.max == 1);
+  }
+
+  {
+    // check in ascending order
+    int a[] = {1, 2, 3};
+    auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 3)));
+    auto ret = std::ranges::minmax(range);
+    assert(ret.min == 1);
+    assert(ret.max == 3);
+  }
+
+  {
+    // check in descending order
+    int a[] = {3, 2, 1};
+    auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 3)));
+    auto ret = std::ranges::minmax(range);
+    assert(ret.min == 1);
+    assert(ret.max == 3);
+  }
+}
+
+constexpr void test_range() {
+  test_range_types<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>();
+  test_range_types<forward_iterator<int*>>();
+  test_range_types<bidirectional_iterator<int*>>();
+  test_range_types<random_access_iterator<int*>>();
+  test_range_types<contiguous_iterator<int*>>();
+
+  {
+    // check that std::invoke is used for the predicate
+    struct S {
+      int i;
+    };
+    S b[3] = {S{2}, S{1}, S{3}};
+    std::same_as<std::ranges::minmax_result<S>> auto ret = std::ranges::minmax(b, {}, &S::i);
+    assert(ret.min.i == 1);
+    assert(ret.max.i == 3);
+  }
+
+  {
+    // check that std::invoke is used for the comparator
+    struct S {
+      int i;
+      constexpr bool comp(S rhs) const { return i < rhs.i; }
+    };
+    S a[] = {{1}, {2}, {3}, {4}};
+    auto ret = std::ranges::minmax(a, &S::comp);
+    assert(ret.min.i == 1);
+    assert(ret.max.i == 4);
+  }
+
+  {
+    // check that the leftmost value for min an rightmost for max are returned
+    struct S {
+      int comp;
+      int other;
+    };
+    S a[] = { {0, 0}, {0, 2}, {0, 1} };
+    auto ret = std::ranges::minmax(a, {}, &S::comp);
+    assert(ret.min.comp == 0);
+    assert(ret.max.comp == 0);
+    assert(ret.min.other == 0);
+    assert(ret.max.other == 1);
+  }
+
+  {
+    // check that an rvalue array works
+    int a[] = {1, 2, 3, 4};
+    auto ret = std::ranges::minmax(std::move(a));
+    assert(ret.min == 1);
+    assert(ret.max == 4);
+  }
+}
+
+constexpr bool test() {
+  test_2_arguments();
+  test_initializer_list();
+  test_range();
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  {
+    // check that the iterator isn't moved from multiple times
+    std::shared_ptr<int> a[] = { std::make_shared<int>(42) };
+    auto range = std::ranges::subrange(std::move_iterator(a), std::move_iterator(a + 1));
+    auto [min, max] = std::ranges::minmax(range);
+    assert(a[0] == nullptr);
+    assert(min != nullptr);
+    assert(max == min);
+  }
+
+  return 0;
+}

libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax_element.pass.cpp

@@ -0,0 +1,316 @@
+//===----------------------------------------------------------------------===//
+//
+// 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<forward_iterator I, sentinel_for<I> S, class Proj = identity,
+//    indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>
+//  constexpr ranges::minmax_element_result<I> ranges::minmax_element(I first, S last, Comp comp = {}, Proj proj = {});
+//
+//  template<forward_range R, class Proj = identity,
+//    indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less>
+//  constexpr ranges::minmax_element_result<borrowed_iterator_t<R>>
+//    ranges::minmax_element(R&& r, Comp comp = {}, Proj proj = {});
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+template <class T>
+concept HasMinMaxElementR = requires(T t) { std::ranges::minmax_element(t); };
+
+struct NoLessThanOp {};
+struct NotTotallyOrdered {
+  int i;
+  bool operator<(const NotTotallyOrdered& o) const { return i < o.i; }
+};
+
+static_assert(HasMinMaxElementR<int (&)[10]>); // make sure HasMinMaxElementR works with an array
+static_assert(!HasMinMaxElementR<NoLessThanOp (&)[10]>);
+static_assert(!HasMinMaxElementR<NotTotallyOrdered (&)[10]>);
+
+static_assert(HasMinMaxElementR<std::initializer_list<int>>); // make sure HasMinMaxElementR works with an initializer_list
+static_assert(!HasMinMaxElementR<std::initializer_list<NoLessThanOp>>);
+static_assert(!HasMinMaxElementR<std::initializer_list<NotTotallyOrdered>>);
+static_assert(!HasMinMaxElementR<InputRangeNotDerivedFrom>);
+static_assert(!HasMinMaxElementR<InputRangeNotIndirectlyReadable>);
+static_assert(!HasMinMaxElementR<InputRangeNotInputOrOutputIterator>);
+static_assert(!HasMinMaxElementR<InputRangeNotSentinelSemiregular>);
+static_assert(!HasMinMaxElementR<InputRangeNotSentinelEqualityComparableWith>);
+
+template <class It, class Sent = sentinel_wrapper<It>>
+concept HasMinMaxElementIt = requires(It it, Sent sent) { std::ranges::minmax_element(it, sent); };
+static_assert(HasMinMaxElementIt<int*>); // make sure HasMinMaxElementIt works
+static_assert(!HasMinMaxElementIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasMinMaxElementIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasMinMaxElementIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasMinMaxElementIt<int*, SentinelForNotSemiregular>);
+static_assert(!HasMinMaxElementIt<int*, SentinelForNotWeaklyEqualityComparableWith>);
+
+static_assert(std::is_same_v<std::ranges::minmax_element_result<int>, std::ranges::min_max_result<int>>);
+
+template <class It>
+constexpr void test_iterators(std::initializer_list<int> a, int expectedMin, int expectedMax) {
+  using Expected = std::ranges::minmax_element_result<It>;
+  const int* first = a.begin();
+  const int* last = a.end();
+  {
+    std::same_as<Expected> auto it = std::ranges::minmax_element(It(first), It(last));
+    assert(base(it.min) == first + expectedMin);
+    assert(base(it.max) == first + expectedMax);
+  }
+  {
+    using Sent = sentinel_wrapper<It>;
+    std::same_as<Expected> auto it = std::ranges::minmax_element(It(first), Sent(It(last)));
+    assert(base(it.min) == first + expectedMin);
+    assert(base(it.max) == first + expectedMax);
+  }
+  {
+    auto range = std::ranges::subrange(It(first), It(last));
+    std::same_as<Expected> auto it = std::ranges::minmax_element(range);
+    assert(base(it.min) == first + expectedMin);
+    assert(base(it.max) == first + expectedMax);
+  }
+  {
+    using Sent = sentinel_wrapper<It>;
+    auto range = std::ranges::subrange(It(first), Sent(It(last)));
+    std::same_as<Expected> auto it = std::ranges::minmax_element(range);
+    assert(base(it.min) == first + expectedMin);
+    assert(base(it.max) == first + expectedMax);
+  }
+}
+
+template <class It>
+constexpr bool test_iterators() {
+  test_iterators<It>({}, 0, 0);
+  test_iterators<It>({1}, 0, 0);
+  test_iterators<It>({1, 2}, 0, 1);
+  test_iterators<It>({2, 1}, 1, 0);
+  test_iterators<It>({2, 1, 2}, 1, 2);
+  test_iterators<It>({2, 1, 1}, 1, 0);
+  test_iterators<It>({2, 2, 1}, 2, 1);
+
+  return true;
+}
+
+constexpr void test_borrowed_range_and_sentinel() {
+  int a[] = {7, 6, 1, 3, 5, 1, 2, 4};
+
+  std::ranges::minmax_element_result<int*> ret = std::ranges::minmax_element(std::views::all(a));
+  assert(ret.min == a + 2);
+  assert(ret.max == a + 0);
+  assert(*ret.min == 1);
+  assert(*ret.max == 7);
+}
+
+constexpr void test_comparator() {
+  int a[] = {7, 6, 9, 3, 5, 1, 2, 4};
+  std::ranges::minmax_element_result<int*> ret = std::ranges::minmax_element(a, std::ranges::greater{});
+  assert(ret.min == a + 2);
+  assert(ret.max == a + 5);
+  assert(*ret.min == 9);
+  assert(*ret.max == 1);
+}
+
+constexpr void test_projection() {
+  {
+    int a[] = {7, 6, 9, 3, 5, 1, 2, 4};
+    std::ranges::minmax_element_result<int*> ret =
+        std::ranges::minmax_element(a, std::ranges::less{}, [](int i) { return i == 5 ? -100 : i; });
+    assert(ret.min == a + 4);
+    assert(ret.max == a + 2);
+    assert(*ret.min == 5);
+    assert(*ret.max == 9);
+  }
+  {
+    int a[] = {7, 6, 9, 3, 5, 1, 2, 4};
+    std::ranges::minmax_element_result<int*> ret =
+        std::ranges::minmax_element(a, std::less<int*>{}, [](int& i) { return &i; });
+    assert(ret.min == a + 0);
+    assert(ret.max == a + 7);
+    assert(*ret.min == 7);
+    assert(*ret.max == 4);
+  }
+}
+
+struct Immobile {
+  int i;
+
+  constexpr Immobile(int i_) : i(i_) {}
+  Immobile(const Immobile&) = delete;
+  Immobile(Immobile&&) = delete;
+
+  auto operator<=>(const Immobile&) const = default;
+};
+
+constexpr void test_immobile() {
+  {
+    Immobile arr[]{1, 2, 3};
+    auto ret = std::ranges::minmax_element(arr);
+    assert(ret.min == arr + 0);
+    assert(ret.max == arr + 2);
+  }
+  {
+    Immobile arr[]{1, 2, 3};
+    auto ret = std::ranges::minmax_element(arr, arr + 3);
+    assert(ret.min == arr + 0);
+    assert(ret.max == arr + 2);
+  }
+}
+
+constexpr void test_dangling() {
+  int compares = 0;
+  int projections = 0;
+  auto comparator = [&](int a, int b) {
+    ++compares;
+    return a < b;
+  };
+  auto projection = [&](int a) {
+    ++projections;
+    return a;
+  };
+  [[maybe_unused]] std::same_as<std::ranges::minmax_element_result<std::ranges::dangling>> auto ret =
+      std::ranges::minmax_element(std::array{1, 2, 3}, comparator, projection);
+  assert(compares == 3);
+  assert(projections == 6);
+}
+
+constexpr bool test() {
+  test_iterators<forward_iterator<const int*>>();
+  test_iterators<bidirectional_iterator<const int*>>();
+  test_iterators<random_access_iterator<const int*>>();
+  test_iterators<contiguous_iterator<const int*>>();
+  test_iterators<const int*>();
+  test_iterators<int*>();
+
+  test_borrowed_range_and_sentinel();
+  test_comparator();
+  test_projection();
+  test_dangling();
+
+  { // check that std::invoke is used
+    {
+      struct S {
+        int i;
+      };
+      S b[3] = {S{2}, S{1}, S{3}};
+      std::same_as<std::ranges::minmax_element_result<S*>> auto ret = std::ranges::minmax_element(b, {}, &S::i);
+      assert(ret.min->i == 1);
+      assert(ret.max->i == 3);
+      assert(ret.min == b + 1);
+      assert(ret.max == b + 2);
+    }
+    {
+      struct S {
+        int i;
+      };
+      S b[3] = {S{2}, S{1}, S{3}};
+      std::same_as<std::ranges::minmax_element_result<S*>> auto ret = std::ranges::minmax_element(b, b + 3, {}, &S::i);
+      assert(ret.min->i == 1);
+      assert(ret.max->i == 3);
+      assert(ret.min == b + 1);
+      assert(ret.max == b + 2);
+    }
+  }
+
+  { // check that the leftmost value for min an rightmost for max are returned
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::minmax_element(a, a + 3, {}, &S::comp);
+      assert(ret.min->comp == 0);
+      assert(ret.max->comp == 0);
+      assert(ret.min->other == 0);
+      assert(ret.max->other == 1);
+    }
+    {
+      struct S {
+        int comp;
+        int other;
+      };
+      S a[] = { {0, 0}, {0, 2}, {0, 1} };
+      auto ret = std::ranges::minmax_element(a, {}, &S::comp);
+      assert(ret.min->comp == 0);
+      assert(ret.max->comp == 0);
+      assert(ret.min->other == 0);
+      assert(ret.max->other == 1);
+    }
+  }
+
+  { // check that an empty range works
+    {
+      std::array<int, 0> a = {};
+      auto ret = std::ranges::minmax_element(a.begin(), a.end());
+      assert(ret.min == a.begin());
+      assert(ret.max == a.begin());
+    }
+    {
+      std::array<int, 0> a = {};
+      auto ret = std::ranges::minmax_element(a);
+      assert(ret.min == a.begin());
+      assert(ret.max == a.begin());
+    }
+  }
+
+  { // check in ascending order
+    {
+      int a[] = {1, 2, 3};
+      auto ret = std::ranges::minmax_element(a, a + 3);
+      assert(ret.min == a + 0);
+      assert(ret.max == a + 2);
+      assert(*ret.min == 1);
+      assert(*ret.max == 3);
+    }
+    {
+      int a[] = {1, 2, 3};
+      auto ret = std::ranges::minmax_element(a);
+      assert(ret.min == a + 0);
+      assert(ret.max == a + 2);
+      assert(*ret.min == 1);
+      assert(*ret.max == 3);
+    }
+  }
+
+  { // check in descending order
+    {
+      int a[] = {3, 2, 1};
+      auto ret = std::ranges::minmax_element(a, a + 3);
+      assert(ret.min == a + 2);
+      assert(ret.max == a + 0);
+      assert(*ret.min == 1);
+      assert(*ret.max == 3);
+    }
+    {
+      int a[] = {3, 2, 1};
+      auto ret = std::ranges::minmax_element(a);
+      assert(ret.min == a + 2);
+      assert(ret.max == a + 0);
+      assert(*ret.min == 1);
+      assert(*ret.max == 3);
+    }
+  }
+
+  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

@@ -101,8 +101,8 @@ static_assert(test(std::ranges::max_element, a));
 //static_assert(test(std::ranges::merge, a, a, a));
 static_assert(test(std::ranges::min, a));
 static_assert(test(std::ranges::min_element, a));
-//static_assert(test(std::ranges::minmax, a));
-//static_assert(test(std::ranges::minmax_element, a));
+static_assert(test(std::ranges::minmax, a));
+static_assert(test(std::ranges::minmax_element, a));
 static_assert(test(std::ranges::mismatch, a, a));
 //static_assert(test(std::ranges::move, a, a));
 //static_assert(test(std::ranges::move_backward, a, a));