[libcxx-commits] [libcxx] [libc++][ranges] P3060R3: Add `std::views::indices(n)` (PR #146823)

[A. Jiang via libcxx-commits]

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@@ -0,0 +1,99 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++26
+
+// ranges
+
+// inline constexpr unspecified indices = unspecified;
+
+#include <cassert>
+#include <cstddef>
+#include <ranges>
+#include <vector>
+
+#include "test_macros.h"
+#define TEST_HAS_NO_INT128 // Size cannot be larger than 64 bits
+#include "type_algorithms.h"
+
+#include "types.h"
+
+// Test SFINAE.
+
+template <typename SizeType>
+concept HasIndices = requires(SizeType s) { std::ranges::views::indices(s); };
+
+struct NotIntegerLike {};
+
+void test_SFINAE() {
+  static_assert(HasIndices<std::size_t>);
+  types::for_each(types::integer_types(), []<typename T> { static_assert(HasIndices<T>); });
+
+  // Non-integer-like types should not satisfy HasIndices
+  static_assert(!HasIndices<bool>);
+  static_assert(!HasIndices<float>);
+  static_assert(!HasIndices<void>);
+  static_assert(!HasIndices<SomeInt>); // Does satisfy is_integer_like, but not the conversion to std::size_t
+  static_assert(!HasIndices<NotIntegerLike>);
+}
+
+constexpr bool test() {
+  {
+    auto indices_view = std::ranges::views::indices(5);
+    static_assert(std::ranges::range<decltype(indices_view)>);
+
+    assert(indices_view.size() == 5);
+
+    assert(indices_view[0] == 0);
+    assert(indices_view[1] == 1);
+    assert(indices_view[2] == 2);
+    assert(indices_view[3] == 3);
+    assert(indices_view[4] == 4);
+  }
+
+  {
+    std::vector v(5, 0);
+
+    auto indices_view = std::ranges::views::indices(std::ranges::size(v));
+    static_assert(std::ranges::range<decltype(indices_view)>);
+
+    assert(indices_view.size() == 5);
+
+    assert(indices_view[0] == 0);
+    assert(indices_view[1] == 1);
+    assert(indices_view[2] == 2);
+    assert(indices_view[3] == 3);
+    assert(indices_view[4] == 4);
+  }
+
+  {
+    std::vector v(5, SomeInt{});
+
+    auto indices_view = std::ranges::views::indices(std::ranges::size(v));
+    static_assert(std::ranges::range<decltype(indices_view)>);
+
+    assert(indices_view.size() == 5);
+
+    assert(indices_view[0] == 0);
+    assert(indices_view[1] == 1);
+    assert(indices_view[2] == 2);
+    assert(indices_view[3] == 3);
+    assert(indices_view[4] == 4);
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test_SFINAE();
----------------
frederick-vs-ja wrote:

Looks like that we don't need to call this function. Well-formedness check should be sufficient.

https://github.com/llvm/llvm-project/pull/146823