1 files changed, 41 insertions, 0 deletions
diff --git a/libcxx/include/__iterator/mergeable.h b/libcxx/include/__iterator/mergeable.h
new file mode 100644
index 000000000000..b9f2d081dc7e
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+++ b/libcxx/include/__iterator/mergeable.h
@@ -0,0 +1,41 @@
+// -*- 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___ITERATOR_MERGEABLE_H
+#define _LIBCPP___ITERATOR_MERGEABLE_H
+
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/ranges_operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/projected.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17
+
+template <class _Input1, class _Input2, class _Output,
+          class _Comp = ranges::less, class _Proj1 = identity, class _Proj2 = identity>
+concept mergeable =
+    input_iterator<_Input1> &&
+    input_iterator<_Input2> &&
+    weakly_incrementable<_Output> &&
+    indirectly_copyable<_Input1, _Output> &&
+    indirectly_copyable<_Input2, _Output> &&
+    indirect_strict_weak_order<_Comp, projected<_Input1, _Proj1>, projected<_Input2, _Proj2>>;
+
+#endif // _LIBCPP_STD_VER > 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___ITERATOR_MERGEABLE_H