[libcxx-commits] [libcxx] [libc++][c++23] P2374: `views::cartesian_product` (PR #111215)

[Hristo Hristov via libcxx-commits]

================
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+#include <ranges>
+#include <cassert>
+#include <vector>
+#include <string>
+
+constexpr bool test() {
+  struct ConstexprStringStream {
+    std::string str;
+
+    constexpr ConstexprStringStream& operator<<(int x) { return *this << char(x + 48); }
+    constexpr ConstexprStringStream& operator<<(char c) {
+      str += c;
+      return *this;
+    }
+  };
+
+  const std::vector<int> v{0, 1, 2};
+  ConstexprStringStream out;
+  for (auto&& [a, b, c] : std::ranges::views::cartesian_product(v, v, v)) {
+    out << a << ' ' << b << ' ' << c << '\n';
+  }
+
+  const std::string_view expected =
+      "0 0 0\n"
+      "0 0 1\n"
+      "0 0 2\n"
+      "0 1 0\n"
+      "0 1 1\n"
+      "0 1 2\n"
+      "0 2 0\n"
+      "0 2 1\n"
+      "0 2 2\n"
+      "1 0 0\n"
+      "1 0 1\n"
+      "1 0 2\n"
+      "1 1 0\n"
+      "1 1 1\n"
+      "1 1 2\n"
+      "1 2 0\n"
+      "1 2 1\n"
+      "1 2 2\n"
+      "2 0 0\n"
+      "2 0 1\n"
+      "2 0 2\n"
+      "2 1 0\n"
+      "2 1 1\n"
+      "2 1 2\n"
+      "2 2 0\n"
+      "2 2 1\n"
+      "2 2 2\n";
+  assert(out.str == expected);
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+  return 0;
+}
----------------
H-G-Hristov wrote:

```suggestion
}
```

+ empty line

https://github.com/llvm/llvm-project/pull/111215