[libcxx-commits] [libcxx] [libc++][ranges] implement `std::ranges::zip_transform_view` (PR #79605)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,94 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// constexpr explicit zip_transform_view(F, Views...)
+
+#include <ranges>
+
+#include "types.h"
+
+template <class T, class... Args>
+concept IsImplicitlyConstructible = requires(T val, Args... args) { val = {std::forward<Args>(args)...}; };
+
+// test constructor is explicit
+static_assert(std::constructible_from<std::ranges::zip_transform_view<Fn, IntView>, Fn, IntView>);
+static_assert(!IsImplicitlyConstructible<std::ranges::zip_transform_view<Fn, IntView>, Fn, IntView>);
+
+static_assert(std::constructible_from<std::ranges::zip_transform_view<Fn, IntView, IntView>, Fn, IntView, IntView>);
+static_assert(!IsImplicitlyConstructible<std::ranges::zip_transform_view<Fn, IntView, IntView>, Fn, IntView, IntView>);
+
+struct MoveAwareView : std::ranges::view_base {
+  int moves                 = 0;
+  constexpr MoveAwareView() = default;
+  constexpr MoveAwareView(MoveAwareView&& other) : moves(other.moves + 1) { other.moves = 1; }
+  constexpr MoveAwareView& operator=(MoveAwareView&& other) {
+    moves       = other.moves + 1;
+    other.moves = 0;
+    return *this;
+  }
+  constexpr const int* begin() const { return &moves; }
+  constexpr const int* end() const { return &moves + 1; }
+};
+
+template <class View1, class View2>
+constexpr void constructorTest(auto&& buffer1, auto&& buffer2) {
+  std::ranges::zip_transform_view v{MakeTuple{}, View1{buffer1}, View2{buffer2}};
+  auto [i, j] = *v.begin();
+  assert(i == buffer1[0]);
+  assert(j == buffer2[0]);
+};
+
+constexpr bool test() {
+  int buffer[8]  = {1, 2, 3, 4, 5, 6, 7, 8};
+  int buffer2[4] = {9, 8, 7, 6};
+
+  {
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ldionne wrote:

IMO we should have tests for 1, 2, 3 and maybe 4 ranges. You already have 2 and 3.

https://github.com/llvm/llvm-project/pull/79605