[gcc(refs/users/ppalka/heads/libstdcxx-constrained-algos)] Add ranges::rotate_copy

[Patrick Palka]

https://gcc.gnu.org/g:57f87946527ec547055b9e912f5f60c596d9a367

commit 57f87946527ec547055b9e912f5f60c596d9a367
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Jan 23 12:26:13 2020 -0500

    Add ranges::rotate_copy

Diff:
---
 libstdc++-v3/include/bits/ranges_algo.h            | 29 +++++++
 .../25_algorithms/rotate_copy/constrained.cc       | 93 ++++++++++++++++++++++
 2 files changed, 122 insertions(+)

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 617c173..bd5c583 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -1920,6 +1920,35 @@ namespace ranges
 			    ranges::end(__r));
     }
 
+  template<typename _Iter, typename _Out>
+  using rotate_copy_result = copy_result<_Iter, _Out>;
+
+  template<forward_iterator _Iter, sentinel_for<_Iter> S,
+	   weakly_incrementable _Out>
+    requires indirectly_copyable<_Iter, _Out>
+    constexpr rotate_copy_result<_Iter, _Out>
+    rotate_copy(_Iter __first, _Iter __middle, S __last, _Out __result)
+    {
+      auto __copy1 = ranges::copy(__middle,
+				  std::move(__last),
+				  std::move(__result));
+      auto __copy2 = ranges::copy(std::move(__first),
+				  std::move(__middle),
+				  std::move(__copy1.out));
+      return { std::move(__copy1.in), std::move(__copy2.out) };
+    }
+
+  template<forward_range _Range, weakly_incrementable _Out>
+    requires indirectly_copyable<iterator_t<_Range>, _Out>
+    constexpr rotate_copy_result<safe_iterator_t<_Range>, _Out>
+    rotate_copy(_Range&& __r, iterator_t<_Range> __middle, _Out __result)
+    {
+      return ranges::rotate_copy(ranges::begin(__r),
+				 std::move(__middle),
+				 ranges::end(__r),
+				 std::move(__result));
+    }
+
 } // namespace ranges
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
diff --git a/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constrained.cc b/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constrained.cc
new file mode 100644
index 0000000..f036377
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constrained.cc
@@ -0,0 +1,93 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <algorithm>
+#include <testsuite_hooks.h>
+#include <testsuite_iterators.h>
+
+using __gnu_test::test_container;
+using __gnu_test::test_range;
+using __gnu_test::forward_iterator_wrapper;
+using __gnu_test::random_access_iterator_wrapper;
+
+namespace ranges = std::ranges;
+
+struct X
+{
+  int i;
+  X () : i(0) { }
+  X (int a) : i(a) { }
+
+  friend bool
+  operator==(const X& lhs, const X& rhs)
+  {
+    return lhs.i == rhs.i;
+  }
+};
+
+static_assert(!std::is_trivial_v<X>);
+
+template<template<typename, template<typename> typename> typename container,
+	 template<typename> typename wrapper,
+	 typename T = int>
+void
+test01()
+{
+  for (int a = 0; a <= 7; a++)
+    {
+      T x[] = {1, 2, 3, 4, 5, 6, 7};
+      T w[7];
+      container<T, wrapper> rx(x), rw(w);
+      auto i = ranges::begin(rx);
+      std::advance(i, a);
+      auto [in,out] = ranges::rotate_copy(rx, i, ranges::begin(rw));
+      VERIFY( in == ranges::end(rx) );
+      VERIFY( out == ranges::end(rw) );
+      for (int k = 0; k < 7; k++)
+	VERIFY( w[k] == (k+a)%7 + 1 );
+    }
+}
+
+constexpr bool
+test02()
+{
+  const int x[] = {1, 2, 3, 4};
+  int w[3];
+  const int y[] = { 2, 3, 1};
+  auto [in,out] = ranges::rotate_copy(x, x+1, x+3, w);
+  return (in == x+3
+	  && out == w+3
+	  && ranges::equal(w, y));
+}
+
+int
+main()
+{
+  test01<test_container, forward_iterator_wrapper>();
+  test01<test_range, forward_iterator_wrapper>();
+
+  test01<test_container, random_access_iterator_wrapper>();
+  test01<test_range, random_access_iterator_wrapper>();
+
+  test01<test_container, random_access_iterator_wrapper, X>();
+  test01<test_range, random_access_iterator_wrapper, X>();
+
+  static_assert(test02());
+}