[Mlir-commits] [mlir] [libc++] Implement ranges::contains_subrange (PR #66963)

[llvmlistbot at llvm.org]

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+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_CONTAINS_SUBRANGE_H
+#define _LIBCPP___ALGORITHM_RANGES_CONTAINS_SUBRANGE_H
+
+#include <__algorithm/ranges_starts_with.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/ranges_operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/indirectly_comparable.h>
+#include <__iterator/projected.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 23
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __contains_subrange {
+struct __fn {
+  template <input_iterator _Iter1,
+            sentinel_for<_Iter1> _Sent1,
+            input_iterator _Iter2,
+            sentinel_for<_Iter2> _Sent2,
+            class _Pred,
+            class _Proj1,
+            class _Proj2,
+            class _Offset = int>
+  static _LIBCPP_HIDE_FROM_ABI constexpr bool __contains_subrange_fn_impl(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred& __pred,
+      _Proj1& __proj1,
+      _Proj2& __proj2,
+      _Offset __offset) {
+    if (__offset < 0)
+      return false;
+    else {
+      for (; __offset >= 0; __offset--, __first1++) {
+        auto result = ranges::starts_with(
+            std::move(__first1),
+            std::move(__last1),
+            std::move(__first2),
+            std::move(__last2),
+            std::ref(__pred),
+            std::ref(__proj1),
+            std::ref(__proj2));
+        if (result)
+          return true;
+      }
+      return false;
+    }
+  }
+
+  template <input_iterator _Iter1,
+            sentinel_for<_Iter1> _Sent1,
+            input_iterator _Iter2,
+            sentinel_for<_Iter2> _Sent2,
+            class _Pred  = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
+    requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred __pred   = {},
+      _Proj1 __proj1 = {},
+      _Proj2 __proj2 = {}) const {
+    int __n1     = ranges::distance(__first1, __last1);
+    int __n2     = ranges::distance(__first2, __last2);
+    int __offset = __n1 - __n2;
----------------
huixie90 wrote:

This still does not work.  `iter_difference_t` could be any integer class type, which is not guaranteed  to be explicitly convertible to `int`. Even it does, you don't want to do it, because this might be a narrowing conversion and you just get into undefined behaviour if actual distance is larger than the max of `int`

https://github.com/llvm/llvm-project/pull/66963