Implement ranges::replace_copy_if

stl/inc/algorithm

@@ -3095,6 +3095,67 @@ _FwdIt2 replace_copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _
 
 #ifdef __cpp_lib_concepts
 namespace ranges {
+    // ALIAS TEMPLATE replace_copy_if_result
+    template <class _In, class _Out>
+    using replace_copy_if_result = in_out_result<_In, _Out>;
+
+    // VARIABLE ranges::replace_copy_if
+    class _Replace_copy_if_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 _Ty, output_iterator<const _Ty&> _Out,
+            class _Pj = identity, indirect_unary_predicate<projected<_It, _Pj>> _Pr>
+            requires indirectly_copyable<_It, _Out>
+        constexpr replace_copy_if_result<_It, _Out> operator()(
+            _It _First, _Se _Last, _Out _Result, _Pr _Pred, const _Ty& _Newval, _Pj _Proj = {}) const {
+            _Adl_verify_range(_First, _Last);
+            auto _UResult = _Replace_copy_if_unchecked(_Get_unwrapped(_STD move(_First)),
+                _Get_unwrapped(_STD move(_Last)), _STD move(_Result), _Pass_fn(_Pred), _Newval, _Pass_fn(_Proj));
+
+            _Seek_wrapped(_First, _STD move(_UResult.in));
+            return {_STD move(_First), _STD move(_UResult.out)};
+        }
+
+        template <input_range _Rng, class _Ty, output_iterator<const _Ty&> _Out, class _Pj = identity,
+            indirect_unary_predicate<projected<iterator_t<_Rng>, _Pj>> _Pr>
+            requires indirectly_copyable<iterator_t<_Rng>, _Out>
+        constexpr replace_copy_if_result<borrowed_iterator_t<_Rng>, _Out> operator()(
+            _Rng&& _Range, _Out _Result, _Pr _Pred, const _Ty& _Newval, _Pj _Proj = {}) const {
+            auto _First   = _RANGES begin(_Range);
+            auto _UResult = _Replace_copy_if_unchecked(_Get_unwrapped(_STD move(_First)), _Uend(_Range),
+                _STD move(_Result), _Pass_fn(_Pred), _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 _Ty, class _Out, class _Pj, class _Pr>
+        _NODISCARD static constexpr replace_copy_if_result<_It, _Out> _Replace_copy_if_unchecked(
+            _It _First, const _Se _Last, _Out _Result, _Pr _Pred, const _Ty& _Newval, _Pj _Proj) {
+            // copy [_First, _Last) to _Out while replacing _Oldval with _Newval if projected _Oldval fulfuills _Pred
+            _STL_INTERNAL_STATIC_ASSERT(input_iterator<_It>);
+            _STL_INTERNAL_STATIC_ASSERT(sentinel_for<_Se, _It>);
+            _STL_INTERNAL_STATIC_ASSERT(output_iterator<_Out, const _Ty&>);
+            _STL_INTERNAL_STATIC_ASSERT(indirectly_copyable<_It, _Out>);
+            _STL_INTERNAL_STATIC_ASSERT(indirect_unary_predicate<_Pr, projected<_It, _Pj>>);
+
+            for (; _First != _Last; ++_First, (void) ++_Result) {
+                if (_STD invoke(_Pred, _STD invoke(_Proj, *_First))) {
+                    *_Result = _Newval;
+                } else {
+                    *_Result = *_First;
+                }
+            }
+
+            return {_STD move(_First), _STD move(_Result)};
+        }
+    };
+
+    inline constexpr _Replace_copy_if_fn replace_copy_if{_Not_quite_object::_Construct_tag{}};
+
     // VARIABLE ranges::fill
     class _Fill_fn : private _Not_quite_object {
     public:

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_if
 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_if/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_if/test.cpp

@@ -0,0 +1,59 @@
+// 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>;
+
+constexpr auto matches = [](int const val) { return val == 47; };
+
+// Validate that replace_copy_if_result aliases in_out_result
+STATIC_ASSERT(same_as<ranges::replace_copy_if_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), matches, 5)),
+    ranges::replace_copy_if_result<ranges::dangling, int*>>);
+STATIC_ASSERT(same_as<decltype(ranges::replace_copy(borrowed<true>{}, static_cast<int*>(nullptr), matches, 5)),
+    ranges::replace_copy_if_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, ranges::indirectly_writable<ranges::range_reference_t<Read>> Write>
+    static constexpr void call() {
+        using ranges::replace_copy_if, ranges::replace_copy_if_result, ranges::iterator_t;
+        { // Validate iterator + sentinel overload
+            Read wrapped_input{input};
+            P input[5] = {{-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}};
+
+            auto result = replace_copy_if(
+                wrapped_input.begin(), wrapped_input.end(), Write{output}, matches, P{47, 1}, get_second);
+            STATIC_ASSERT(same_as<decltype(result), replace_copy_if_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
+            Read wrapped_input{input};
+            P input[5] = {{-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}, {-1, -1}};
+
+            auto result = replace_copy_if(wrapped_input, Write{output}, matches, P{47, 1}, get_second);
+            STATIC_ASSERT(same_as<decltype(result), replace_copy_if_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>();
+}