[libcxx-commits] [libcxx] [libc++][ranges] implement `ranges::elements_of` (PR #91414)

[Mark de Wever via libcxx-commits]

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@@ -0,0 +1,55 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___RANGES_ELEMENTS_OF_H
+#define _LIBCPP___RANGES_ELEMENTS_OF_H
+
+#include <__config>
+#include <__memory/allocator.h>
+#include <__ranges/concepts.h>
+#include <__utility/move.h>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+
+template <range _Range, class _Allocator = allocator<byte>>
+struct elements_of {
+  _LIBCPP_NO_UNIQUE_ADDRESS _Range range;
+  _LIBCPP_NO_UNIQUE_ADDRESS _Allocator allocator;
+
+  // This explicit constructor is required because AppleClang 15 hasn't implement P0960R3
+  _LIBCPP_HIDE_FROM_ABI explicit constexpr elements_of(_Range __range, _Allocator __alloc = _Allocator())
+      : range(std::move(__range)), allocator(std::move(__alloc)) {}
+};
+
+template <class _Range, class _Allocator = allocator<byte>>
+// This explicit constraint is required because AppleClang 15 might not deduce the correct type for `_Range` without it
+  requires range<_Range&&>
+elements_of(_Range&&, _Allocator = _Allocator()) -> elements_of<_Range&&, _Allocator>;
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mordante wrote:

Can you add a CTAD test?

https://github.com/llvm/llvm-project/pull/91414