test copied from std

Author: PaulXiCao

libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/example_from_std.pass.cpp

@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// 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;
+  // fixme: replace by views::cartesian_product
+  for (auto&& [a, b, c] : std::ranges::cartesian_product_view(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() {
+  test();
+  static_assert(test());
+}