Implement ranges::replace_copy

stl/inc/algorithm

@@ -3061,6 +3061,72 @@ _FwdIt2 replace_copy(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, cons
 }
 #endif // _HAS_CXX17
 
+#ifdef __cpp_lib_concepts
+namespace ranges {
+    // ALIAS TEMPLATE replace_copy_result
+    template <class _In, class _Out>
+    using replace_copy_result = in_out_result<_In, _Out>;
+
+    // VARIABLE ranges::replace_copy
+    class _Replace_copy_fn : private _Not_quite_object {
+    public:
+        using _Not_quite_object::_Not_quite_object;
+
+        // clang-format off
+        template <input_iterator _It, sentinel_for<_It> _Se, class _Ty1, class _Ty2, output_iterator<const _Ty2&> _Out,
+            class _Pj = identity>
+            requires indirectly_copyable<_It, _Out>
+                  && indirect_binary_predicate<ranges::equal_to, projected<_It, _Pj>, const _Ty1*>
+        constexpr replace_copy_result<_It, _Out> operator()(
+            _It _First, _Se _Last, _Out _Result, const _Ty1& _Oldval, const _Ty2& _Newval, _Pj _Proj = {}) const {
+            _Adl_verify_range(_First, _Last);
+            auto _UResult = _Replace_copy_unchecked(_Get_unwrapped(_STD move(_First)), _Get_unwrapped(_STD move(_Last)),
+                _STD move(_Result), _Oldval, _Newval, _Pass_fn(_Proj));
+
+            _Seek_wrapped(_First, _STD move(_UResult.in));
+            return {_STD move(_First), _STD move(_UResult.out)};
+        }
+
+        template <input_range _Rng, class _Ty1, class _Ty2, output_iterator<const _Ty2&> _Out, class _Pj = identity>
+            requires indirectly_copyable<iterator_t<_Rng>, _Out>
+                  && indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Rng>, _Pj>, const _Ty1*>
+        constexpr replace_copy_result<borrowed_iterator_t<_Rng>, _Out> operator()(
+            _Rng&& _Range, _Out _Result, const _Ty1& _Oldval, const _Ty2& _Newval, _Pj _Proj = {}) const {
+            auto _First   = _RANGES begin(_Range);
+            auto _UResult = _Replace_copy_unchecked(_Get_unwrapped(_STD move(_First)), _Uend(_Range),
+                _STD move(_Result), _Oldval, _Newval, _Pass_fn(_Proj));
+
+            _Seek_wrapped(_First, _STD move(_UResult.in));
+            return {_STD move(_First), _STD move(_UResult.out)};
+        }
+        // clang-format on
+    private:
+        template <class _It, class _Se, class _Ty1, class _Ty2, class _Out, class _Pj>
+        _NODISCARD static constexpr replace_copy_result<_It, _Out> _Replace_copy_unchecked(
+            _It _First, const _Se _Last, _Out _Result, const _Ty1& _Oldval, const _Ty2& _Newval, _Pj _Proj) {
+            // copy [_First, _Last) to _Out while replacing projected _Oldval with _Newval
+            _STL_INTERNAL_STATIC_ASSERT(input_iterator<_It>);
+            _STL_INTERNAL_STATIC_ASSERT(sentinel_for<_Se, _It>);
+            _STL_INTERNAL_STATIC_ASSERT(output_iterator<_Out, const _Ty2&>);
+            _STL_INTERNAL_STATIC_ASSERT(indirectly_copyable<_It, _Out>);
+            _STL_INTERNAL_STATIC_ASSERT(indirect_binary_predicate<equal_to, projected<_It, _Pj>, const _Ty1*>);
+
+            for (; _First != _Last; ++_First, (void) ++_Result) {
+                if (_STD invoke(_Proj, *_First) == _Oldval) {
+                    *_Result = _Newval;
+                } else {
+                    *_Result = *_First;
+                }
+            }
+
+            return {_STD move(_First), _STD move(_Result)};
+        }
+    };
+
+    inline constexpr _Replace_copy_fn replace_copy{_Not_quite_object::_Construct_tag{}};
+} // namespace ranges
+#endif // __cpp_lib_concepts
+
 // FUNCTION TEMPLATE replace_copy_if
 template <class _InIt, class _OutIt, class _Pr, class _Ty>
 _CONSTEXPR20 _OutIt replace_copy_if(_InIt _First, _InIt _Last, _OutIt _Dest, _Pr _Pred, const _Ty& _Val) {

tests/std/test.lst

@@ -261,6 +261,7 @@ tests\P0896R4_ranges_alg_minmax
 tests\P0896R4_ranges_alg_mismatch
 tests\P0896R4_ranges_alg_move
 tests\P0896R4_ranges_alg_none_of
+tests\P0896R4_ranges_alg_replace_copy
 tests\P0896R4_ranges_alg_search
 tests\P0896R4_ranges_alg_search_n
 tests\P0896R4_ranges_alg_swap_ranges

tests/std/tests/P0896R4_ranges_alg_replace_copy/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_replace_copy/test.cpp

@@ -0,0 +1,57 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <algorithm>
+#include <cassert>
+#include <concepts>
+#include <ranges>
+#include <utility>
+
+#include <range_algorithm_support.hpp>
+using namespace std;
+using P = pair<int, int>;
+
+// Validate that replace_copy_result aliases in_out_result
+STATIC_ASSERT(same_as<ranges::replace_copy_result<int, double>, ranges::in_out_result<int, double>>);
+
+// Validate dangling story
+STATIC_ASSERT(same_as<decltype(ranges::replace_copy(borrowed<false>{}, static_cast<int*>(nullptr), 42, 5)),
+    ranges::replace_copy_result<ranges::dangling, int*>>);
+STATIC_ASSERT(same_as<decltype(ranges::replace_copy(borrowed<true>{}, static_cast<int*>(nullptr), 42, 5)),
+    ranges::replace_copy_result<int*, int*>>);
+
+struct instantiator {
+    static constexpr P input[5]    = {{0, 99}, {1, 47}, {2, 99}, {3, 47}, {4, 99}};
+    static constexpr P expected[5] = {{0, 99}, {47, 1}, {2, 99}, {47, 1}, {4, 99}};
+
+    template <ranges::input_range Read, indirectly_writable<ranges::range_reference_t<Read>> Write>
+    static constexpr void call() {
+        using ranges::replace_copy, ranges::replace_copy_result, ranges::iterator_t;
+        { // Validate iterator + sentinel overload
+            P output[5] = {{-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}};
+            Read wrapped_input{input};
+
+            auto result =
+                replace_copy(wrapped_input.begin(), wrapped_input.end(), Write{output}, 47, P{47, 1}, get_second);
+            STATIC_ASSERT(same_as<decltype(result), replace_copy_result<iterator_t<Read>, Write>>);
+            assert(result.in == wrapped_input.end());
+            assert(result.out.peek() == output + 5);
+            assert(ranges::equal(output, expected));
+        }
+        { // Validate range overload
+            P output[5] = {{-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}};
+            Read wrapped_input{input};
+
+            auto result = replace_copy(wrapped_input, Write{output}, 47, P{47, 1}, get_second);
+            STATIC_ASSERT(same_as<decltype(result), replace_copy_result<iterator_t<Read>, Write>>);
+            assert(result.in == wrapped_input.end());
+            assert(result.out.peek() == output + 5);
+            assert(ranges::equal(output, expected));
+        }
+    }
+};
+
+int main() {
+    STATIC_ASSERT((test_in_write<instantiator, P const, P>(), true));
+    test_in_write<instantiator, P const, P>();
+}