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

[Hristo Hristov via libcxx-commits]

================
@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// std::ranges::cartesian_product_view::size
+
+#include <array>
+#include <cassert>
+#include <initializer_list>
+#include <ranges>
+
+constexpr bool test() {
+  { // example taken from: https://en.cppreference.com/w/cpp/ranges/cartesian_product_view/size
+    constexpr static auto w = {1};
+    constexpr static auto x = {2, 3};
+    constexpr static auto y = {4, 5, 6};
+    constexpr static auto z = {7, 8, 9, 10, 11, 12, 13};
+
+    constexpr auto ww = std::ranges::views::all(w);
+    constexpr auto xx = std::ranges::views::all(x);
+    constexpr auto yy = std::ranges::views::all(y);
+    constexpr auto zz = std::ranges::views::all(z);
+
+    constexpr auto v = std::ranges::cartesian_product_view(ww, xx, yy, zz);
+
+    assert(v.size() == 42);
+    assert(v.size() == w.size() * x.size() * y.size() * z.size());
+  }
+
+  { // empty range
+    std::ranges::empty_view<int> e;
+    auto v = std::ranges::cartesian_product_view(e);
+    assert(v.size() == 0);
+  }
+
+  { // 1..3 range(s)
+    constexpr size_t N0 = 3, N1 = 7, N2 = 42;
+    std::array<int, N0> a0;
+    std::array<int, N1> a1;
+    std::array<int, N2> a2;
+    assert(std::ranges::cartesian_product_view(a0).size() == N0);
+    assert(std::ranges::cartesian_product_view(a0, a1).size() == N0 * N1);
+    assert(std::ranges::cartesian_product_view(a0, a1, a2).size() == N0 * N1 * N2);
+  }
+
+  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