[libcxx-commits] [libcxx] [libcxxabi] [libc++][ranges] Implement P1899 `ranges::stride_view`. (PR #65200)

[A. Jiang via libcxx-commits]

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@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++23
+
+// template <input_range _View> requires view<_View>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+#include "test_range.h"
+
+template <typename I, std::ranges::range_difference_t<I> D>
+concept CanStrideView = requires { std::ranges::stride_view<I>{I{}, D}; };
+
+// Ensure that the InputRangeNotIndirectlyReadable is a valid range.
+static_assert(std::ranges::range<InputRangeNotIndirectlyReadable>);
+// Ensure that the InputRangeNotIndirectlyReadable's is not an input range ...
+static_assert(!std::ranges::input_range<std::ranges::iterator_t<InputRangeNotIndirectlyReadable>>);
+// Because CanStrideView requires that the range/view type be default constructible, let's double check that ...
+static_assert(std::is_constructible_v<InputRangeNotIndirectlyReadable>);
+// And now, finally, let's make sure that we cannot stride over a range whose iterator is not an input iterator ...
+static_assert(!CanStrideView<InputRangeNotIndirectlyReadable, 1>);
+
+// Ensure that a range that is not a view cannot be the subject of a stride_view.
+static_assert(std::ranges::range<test_non_const_range<cpp17_input_iterator>>);
+static_assert(std::ranges::input_range<test_non_const_range<cpp17_input_iterator>>);
+static_assert(std::movable<test_non_const_range<cpp17_input_iterator>>);
+static_assert(!std::ranges::view<test_non_const_range<cpp17_input_iterator>>);
+static_assert(!CanStrideView<test_non_const_range<cpp17_input_iterator>, 1>);
+
+// And now, let's satisfy all the prerequisites and make sure that we can stride over a range (that is an input range
+// and is a view!)
+static_assert(std::ranges::range<test_view<cpp17_input_iterator>>);
+static_assert(std::ranges::input_range<test_view<cpp17_input_iterator>>);
+static_assert(std::ranges::view<test_view<cpp17_input_iterator>>);
+static_assert(CanStrideView<test_view<cpp17_input_iterator>, 1>);
+
+int main(int, char**) { return 0; }
----------------
frederick-vs-ja wrote:

Looks like that we should make this file a `.compile.pass.cpp` and remove the `main` function.

https://github.com/llvm/llvm-project/pull/65200