Implement ranges::sort (#1127)

stl/inc/algorithm

@@ -1925,7 +1925,7 @@ namespace ranges {
             auto _UFirst = _Get_unwrapped(_STD move(_First));
             auto _ULast  = _Get_final_iterator_unwrapped<_It1>(_UFirst, _STD move(_Last));
             _Seek_wrapped(_First, _ULast);
-            _Result = _RANGES _Move_backward_common(_STD move(_UFirst), _STD move(_ULast), _STD move(_Result));
+            _Result = _Move_backward_common(_STD move(_UFirst), _STD move(_ULast), _STD move(_Result));
             return {_STD move(_First), _STD move(_Result)};
         }
 
@@ -1933,7 +1933,7 @@ namespace ranges {
             requires indirectly_movable<iterator_t<_Rng>, _It>
         constexpr move_backward_result<borrowed_iterator_t<_Rng>, _It> operator()(_Rng&& _Range, _It _Result) const {
             auto _ULast = _Get_final_iterator_unwrapped(_Range);
-            _Result     = _RANGES _Move_backward_common(_Ubegin(_Range), _ULast, _STD move(_Result));
+            _Result     = _Move_backward_common(_Ubegin(_Range), _ULast, _STD move(_Result));
             return {_Rewrap_iterator(_Range, _STD move(_ULast)), _STD move(_Result)};
         }
         // clang-format on
@@ -6402,7 +6402,7 @@ namespace ranges {
 // FUNCTION TEMPLATE make_heap
 template <class _RanIt, class _Pr>
 _CONSTEXPR20 void _Make_heap_unchecked(_RanIt _First, _RanIt _Last, _Pr _Pred) {
-    // make nontrivial [_First, _Last) into a heap
+    // make [_First, _Last) into a heap
     using _Diff   = _Iter_diff_t<_RanIt>;
     _Diff _Bottom = _Last - _First;
     for (_Diff _Hole = _Bottom >> 1; _Hole > 0;) { // shift for codegen
@@ -6431,8 +6431,8 @@ namespace ranges {
     template <random_access_iterator _It, class _Pr, class _Pj>
         requires sortable<_It, _Pr, _Pj>
     constexpr void _Make_heap_common(_It _First, _It _Last, _Pr _Pred, _Pj _Proj) {
-        // make nontrivial [_First, _Last) into a heap with respect to _Pred and _Proj
         // clang-format on
+        // make [_First, _Last) into a heap with respect to _Pred and _Proj
         using _Diff         = iter_difference_t<_It>;
         const _Diff _Bottom = _Last - _First;
         for (_Diff _Hole = _Bottom >> 1; _Hole > 0;) { // shift for codegen
@@ -6452,6 +6452,7 @@ namespace ranges {
         template <random_access_iterator _It, sentinel_for<_It> _Se, class _Pr = ranges::less, class _Pj = identity>
             requires sortable<_It, _Pr, _Pj>
         constexpr _It operator()(_It _First, _Se _Last, _Pr _Pred = {}, _Pj _Proj = {}) const {
+            // clang-format on
             _Adl_verify_range(_First, _Last);
             auto _UFirst = _Get_unwrapped(_STD move(_First));
             auto _ULast  = _Get_final_iterator_unwrapped<_It>(_UFirst, _STD move(_Last));
@@ -6460,9 +6461,11 @@ namespace ranges {
             return _First;
         }
 
+        // clang-format off
         template <random_access_range _Rng, class _Pr = ranges::less, class _Pj = identity>
             requires sortable<iterator_t<_Rng>, _Pr, _Pj>
         constexpr borrowed_iterator_t<_Rng> operator()(_Rng&& _Range, _Pr _Pred = {}, _Pj _Proj = {}) const {
+            // clang-format on
             if constexpr (common_range<_Rng>) {
                 _Make_heap_common(_Ubegin(_Range), _Uend(_Range), _Pass_fn(_Pred), _Pass_fn(_Proj));
                 return _RANGES end(_Range);
@@ -6472,7 +6475,6 @@ namespace ranges {
                 return _Rewrap_iterator(_Range, _STD move(_ULast));
             }
         }
-        // clang-format on
     };
 
     inline constexpr _Make_heap_fn make_heap{_Not_quite_object::_Construct_tag{}};
@@ -6665,8 +6667,8 @@ namespace ranges {
     template <random_access_iterator _It, class _Pr, class _Pj>
         requires sortable<_It, _Pr, _Pj>
     constexpr void _Sort_heap_common(const _It _First, _It _Last, _Pr _Pred, _Pj _Proj) {
-        // order heap by repeatedly popping
         // clang-format on
+        // order heap by repeatedly popping
         for (; _Last - _First >= 2; --_Last) {
             _RANGES _Pop_heap_unchecked(_First, _Last, _Pred, _Proj);
         }
@@ -6680,6 +6682,7 @@ namespace ranges {
         template <random_access_iterator _It, sentinel_for<_It> _Se, class _Pr = ranges::less, class _Pj = identity>
             requires sortable<_It, _Pr, _Pj>
         constexpr _It operator()(_It _First, _Se _Last, _Pr _Pred = {}, _Pj _Proj = {}) const {
+            // clang-format on
             _Adl_verify_range(_First, _Last);
             auto _UFirst = _Get_unwrapped(_STD move(_First));
             auto _ULast  = _Get_final_iterator_unwrapped<_It>(_UFirst, _STD move(_Last));
@@ -6688,9 +6691,11 @@ namespace ranges {
             return _First;
         }
 
+        // clang-format off
         template <random_access_range _Rng, class _Pr = ranges::less, class _Pj = identity>
             requires sortable<iterator_t<_Rng>, _Pr, _Pj>
         constexpr borrowed_iterator_t<_Rng> operator()(_Rng&& _Range, _Pr _Pred = {}, _Pj _Proj = {}) const {
+            // clang-format on
             if constexpr (common_range<_Rng>) {
                 _Sort_heap_common(_Ubegin(_Range), _Uend(_Range), _Pass_fn(_Pred), _Pass_fn(_Proj));
                 return _RANGES end(_Range);
@@ -6700,7 +6705,6 @@ namespace ranges {
                 return _Rewrap_iterator(_Range, _STD move(_ULast));
             }
         }
-        // clang-format on
     };
 
     inline constexpr _Sort_heap_fn sort_heap{_Not_quite_object::_Construct_tag{}};
@@ -7628,6 +7632,7 @@ void sort(_ExPo&& _Exec, const _RanIt _First, const _RanIt _Last) noexcept /* te
     // order [_First, _Last)
     _STD sort(_STD forward<_ExPo>(_Exec), _First, _Last, less{});
 }
+#endif // _HAS_CXX17
 
 #ifdef __cpp_lib_concepts
 namespace ranges {
@@ -7635,6 +7640,7 @@ namespace ranges {
     template <bidirectional_iterator _It, class _Pr, class _Pj>
         requires sortable<_It, _Pr, _Pj>
     constexpr void _Insertion_sort_common(const _It _First, const _It _Last, _Pr _Pred, _Pj _Proj) {
+        // clang-format on
         // insertion sort [_First, _Last)
 
         if (_First == _Last) { // empty range is sorted
@@ -7643,7 +7649,7 @@ namespace ranges {
 
         for (auto _Mid = _First; ++_Mid != _Last;) { // order next element
             iter_value_t<_It> _Val = _RANGES iter_move(_Mid);
-            auto _Hole            = _Mid;
+            auto _Hole             = _Mid;
 
             for (auto _Prev = _Hole;;) {
                 --_Prev;
@@ -7660,9 +7666,11 @@ namespace ranges {
         }
     }
 
+    // clang-format off
     template <random_access_iterator _It, class _Pr, class _Pj>
         requires sortable<_It, _Pr, _Pj>
-    constexpr void _Med3_unchecked(_It _First, _It _Mid, _It _Last, _Pr _Pred, _Pj _Proj) {
+    constexpr void _Med3_common(_It _First, _It _Mid, _It _Last, _Pr _Pred, _Pj _Proj) {
+        // clang-format on
         // sort median of three elements to middle
         if (_STD invoke(_Pred, _STD invoke(_Proj, *_Mid), _STD invoke(_Proj, *_First))) {
             _RANGES iter_swap(_Mid, _First);
@@ -7680,33 +7688,37 @@ namespace ranges {
         }
     }
 
+    // clang-format off
     template <random_access_iterator _It, class _Pr, class _Pj>
         requires sortable<_It, _Pr, _Pj>
-    constexpr void _Guess_median_unchecked(_It _First, _It _Mid, _It _Last, _Pr _Pred, _Pj _Proj) {
+    constexpr void _Guess_median_common(_It _First, _It _Mid, _It _Last, _Pr _Pred, _Pj _Proj) {
+        // clang-format on
         // sort median element to middle
         using _Diff        = iter_difference_t<_It>;
         const _Diff _Count = _Last - _First;
         if (_Count > 40) { // Tukey's ninther
             const _Diff _Step     = (_Count + 1) >> 3; // +1 can't overflow because range was made inclusive in caller
             const _Diff _Two_step = _Step << 1; // note: intentionally discards low-order bit
-            _Med3_unchecked(_First, _First + _Step, _First + _Two_step, _Pred, _Proj);
-            _Med3_unchecked(_Mid - _Step, _Mid, _Mid + _Step, _Pred, _Proj);
-            _Med3_unchecked(_Last - _Two_step, _Last - _Step, _Last, _Pred, _Proj);
-            _Med3_unchecked(_First + _Step, _Mid, _Last - _Step, _Pred, _Proj);
+            _Med3_common(_First, _First + _Step, _First + _Two_step, _Pred, _Proj);
+            _Med3_common(_Mid - _Step, _Mid, _Mid + _Step, _Pred, _Proj);
+            _Med3_common(_Last - _Two_step, _Last - _Step, _Last, _Pred, _Proj);
+            _Med3_common(_First + _Step, _Mid, _Last - _Step, _Pred, _Proj);
         } else {
-            _Med3_unchecked(_First, _Mid, _Last, _Pred, _Proj);
+            _Med3_common(_First, _Mid, _Last, _Pred, _Proj);
         }
     }
 
+    // clang-format off
     template <random_access_iterator _It, class _Pr, class _Pj>
         requires sortable<_It, _Pr, _Pj>
-    _NODISCARD constexpr subrange<_It> _Partition_by_median_guess_unchecked(
+    _NODISCARD constexpr subrange<_It> _Partition_by_median_guess_common(
         _It _First, _It _Last, _Pr _Pred, _Pj _Proj) {
+        // clang-format on
         // Choose a pivot, partition [_First, _Last) into elements less than pivot, elements equal to pivot, and
         // elements greater than pivot; return the equal partition as a subrange.
 
         _It _Mid = _First + ((_Last - _First) >> 1); // shift for codegen
-        _RANGES _Guess_median_unchecked(_First, _Mid, _RANGES prev(_Last), _Pred, _Proj);
+        _Guess_median_common(_First, _Mid, _RANGES prev(_Last), _Pred, _Proj);
         _It _Pfirst = _Mid;
         _It _Plast  = _RANGES next(_Pfirst);
 
@@ -7716,8 +7728,7 @@ namespace ranges {
             --_Pfirst;
         }
 
-        while (_Plast < _Last
-               && !_STD invoke(_Pred, _STD invoke(_Proj, *_Plast), _STD invoke(_Proj, *_Pfirst))
+        while (_Plast < _Last && !_STD invoke(_Pred, _STD invoke(_Proj, *_Plast), _STD invoke(_Proj, *_Pfirst))
                && !_STD invoke(_Pred, _STD invoke(_Proj, *_Pfirst), _STD invoke(_Proj, *_Plast))) {
             ++_Plast;
         }
@@ -7775,10 +7786,76 @@ namespace ranges {
             }
         }
     }
-    // clang-format on
+
+    // VARIABLE ranges::sort
+    class _Sort_fn : private _Not_quite_object {
+    public:
+        using _Not_quite_object::_Not_quite_object;
+
+        // clang-format off
+        template <random_access_iterator _It, sentinel_for<_It> _Se, class _Pr = ranges::less, class _Pj = identity>
+            requires sortable<_It, _Pr, _Pj>
+        constexpr _It operator()(_It _First, _Se _Last, _Pr _Pred = {}, _Pj _Proj = {}) const {
+            // clang-format on
+            _Adl_verify_range(_First, _Last);
+            auto _UFirst = _Get_unwrapped(_STD move(_First));
+            auto _ULast  = _Get_final_iterator_unwrapped<_It>(_UFirst, _STD move(_Last));
+            _Seek_wrapped(_First, _ULast);
+            const auto _Count = _ULast - _UFirst;
+            _Sort_common(_STD move(_UFirst), _STD move(_ULast), _Count, _Pass_fn(_Pred), _Pass_fn(_Proj));
+            return _First;
+        }
+
+        // clang-format off
+        template <random_access_range _Rng, class _Pr = ranges::less, class _Pj = identity>
+            requires sortable<iterator_t<_Rng>, _Pr, _Pj>
+        constexpr borrowed_iterator_t<_Rng> operator()(_Rng&& _Range, _Pr _Pred = {}, _Pj _Proj = {}) const {
+            // clang-format on
+            auto _UFirst      = _Ubegin(_Range);
+            auto _ULast       = _Get_final_iterator_unwrapped(_Range);
+            const auto _Count = _ULast - _UFirst;
+            _Sort_common(_STD move(_UFirst), _ULast, _Count, _Pass_fn(_Pred), _Pass_fn(_Proj));
+            return _Rewrap_iterator(_Range, _STD move(_ULast));
+        }
+
+    private:
+        template <class _It, class _Pr, class _Pj>
+        static constexpr void _Sort_common(_It _First, _It _Last, iter_difference_t<_It> _Ideal, _Pr _Pred, _Pj _Proj) {
+            // sort [_First, _Last) with respect to _Pred and _Proj
+            _STL_INTERNAL_STATIC_ASSERT(random_access_iterator<_It>);
+            _STL_INTERNAL_STATIC_ASSERT(sortable<_It, _Pr, _Pj>);
+
+            for (;;) {
+                if (_Last - _First <= _ISORT_MAX) { // small
+                    _Insertion_sort_common(_STD move(_First), _STD move(_Last), _Pred, _Proj);
+                    return;
+                }
+
+                if (_Ideal <= 0) { // heap sort if too many divisions
+                    _Make_heap_common(_First, _Last, _Pred, _Proj);
+                    _Sort_heap_common(_STD move(_First), _STD move(_Last), _Pred, _Proj);
+                    return;
+                }
+
+                // divide and conquer by quicksort
+                auto [_Mid_first, _Mid_last] = _Partition_by_median_guess_common(_First, _Last, _Pred, _Proj);
+
+                _Ideal = (_Ideal >> 1) + (_Ideal >> 2); // allow 1.5 log2(N) divisions
+
+                if (_Mid_first - _First < _Last - _Mid_last) { // loop on second half
+                    _Sort_common(_First, _STD move(_Mid_first), _Ideal, _Pred, _Proj);
+                    _First = _STD move(_Mid_last);
+                } else { // loop on first half
+                    _Sort_common(_STD move(_Mid_last), _Last, _Ideal, _Pred, _Proj);
+                    _Last = _STD move(_Mid_first);
+                }
+            }
+        }
+    };
+
+    inline constexpr _Sort_fn sort{_Not_quite_object::_Construct_tag{}};
 } // namespace ranges
 #endif // __cpp_lib_concepts
-#endif // _HAS_CXX17
 
 // FUNCTION TEMPLATE stable_sort
 template <class _FwdIt, class _Ty, class _Pr>
@@ -8184,7 +8261,7 @@ namespace ranges {
             }
 
             while (_ISORT_MAX < _Last - _First) { // divide and conquer, ordering partition containing Nth
-                subrange<_It> _Mid = _RANGES _Partition_by_median_guess_unchecked(_First, _Last, _Pred, _Proj);
+                subrange<_It> _Mid = _Partition_by_median_guess_common(_First, _Last, _Pred, _Proj);
 
                 if (_Mid.end() <= _Nth) {
                     _First = _Mid.end();
@@ -8196,7 +8273,7 @@ namespace ranges {
             }
 
             // sort any remainder
-            _RANGES _Insertion_sort_common(_STD move(_First), _STD move(_Last), _STD move(_Pred), _STD move(_Proj));
+            _Insertion_sort_common(_STD move(_First), _STD move(_Last), _STD move(_Pred), _STD move(_Proj));
         }
     };
 

tests/std/test.lst

@@ -298,6 +298,7 @@ tests\P0896R4_ranges_alg_set_intersection
 tests\P0896R4_ranges_alg_set_symmetric_difference
 tests\P0896R4_ranges_alg_set_union
 tests\P0896R4_ranges_alg_shuffle
+tests\P0896R4_ranges_alg_sort
 tests\P0896R4_ranges_alg_swap_ranges
 tests\P0896R4_ranges_alg_transform_binary
 tests\P0896R4_ranges_alg_transform_unary

tests/std/tests/P0896R4_ranges_alg_sort/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\concepts_matrix.lst

tests/std/tests/P0896R4_ranges_alg_sort/test.cpp

@@ -0,0 +1,61 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <concepts>
+#include <ranges>
+#include <utility>
+
+#include <range_algorithm_support.hpp>
+
+using namespace std;
+using P = pair<int, int>;
+
+// Validate dangling story
+STATIC_ASSERT(same_as<decltype(ranges::sort(borrowed<false>{})), ranges::dangling>);
+STATIC_ASSERT(same_as<decltype(ranges::sort(borrowed<true>{})), int*>);
+
+struct instantiator {
+    static constexpr array input = {P{-1200257975, 0}, P{-1260655766, 1}, P{-1298559576, 2}, P{-1459960308, 3},
+        P{-2095681771, 4}, P{-441494788, 5}, P{-47163201, 6}, P{-912489821, 7}, P{1429106719, 8}, P{1668617627, 9}};
+
+    template <ranges::random_access_range R>
+    static constexpr void call() {
+#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, VSO-938163
+        if constexpr (!ranges::contiguous_range<R>)
+#endif // TRANSITION, VSO-938163
+        {
+            using ranges::sort, ranges::is_sorted, ranges::iterator_t, ranges::less;
+
+            { // Validate range overload
+                auto buff = input;
+                const R range{buff};
+                const same_as<iterator_t<R>> auto result = sort(range, less{}, get_first);
+                assert(result == range.end());
+                assert(is_sorted(range, less{}, get_first));
+            }
+
+            { // Validate iterator overload
+                auto buff = input;
+                const R range{buff};
+                const same_as<iterator_t<R>> auto result = sort(range.begin(), range.end(), less{}, get_first);
+                assert(result == range.end());
+                assert(is_sorted(range.begin(), range.end(), less{}, get_first));
+            }
+
+            { // Validate empty range
+                const R range{};
+                const same_as<iterator_t<R>> auto result = sort(range, less{}, get_first);
+                assert(result == range.end());
+                assert(is_sorted(range, less{}, get_first));
+            }
+        }
+    }
+};
+
+int main() {
+    STATIC_ASSERT((test_random<instantiator, P>(), true));
+    test_random<instantiator, P>();
+}