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

[Patrick Palka]

https://gcc.gnu.org/g:1e627cc4c7bdf6d2259b0ba187ef4cb14b0b0f41

commit 1e627cc4c7bdf6d2259b0ba187ef4cb14b0b0f41
Author: Patrick Palka <ppalka@gcc.gnu.org>
Date:   Mon Jan 20 11:38:31 2020 -0500

    Add ranges::swap_ranges

Diff:
---
 libstdc++-v3/include/bits/ranges_algo.h            |  26 +++++
 .../25_algorithms/swap_ranges/constrained.cc       | 122 +++++++++++++++++++++
 2 files changed, 148 insertions(+)

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 208fdb8..788837d 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -942,6 +942,32 @@ namespace ranges
 			    std::move(__result));
       }
 
+    template<class _Iter1, class _Iter2>
+    using swap_ranges_result = mismatch_result<_Iter1, _Iter2>;
+
+    template<input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
+	     input_iterator _Iter2, sentinel_for<_Iter2> _Sent2>
+      requires indirectly_swappable<_Iter1, _Iter2>
+      constexpr swap_ranges_result<_Iter1, _Iter2>
+      swap_ranges(_Iter1 __first1, _Sent1 __last1,
+		  _Iter2 __first2, _Sent2 __last2)
+      {
+	for (; __first1 != __last1 && __first2 != __last2;
+	     ++__first1, (void)++__first2)
+	  std::swap(*__first1, *__first2);
+	return {__first1, __first2};
+      }
+
+    template<input_range _Range1, input_range _Range2>
+      requires indirectly_swappable<iterator_t<_Range1>, iterator_t<_Range2>>
+      constexpr swap_ranges_result<safe_iterator_t<_Range1>,
+				   safe_iterator_t<_Range2>>
+      swap_ranges(_Range1&& __r1, _Range2&& __r2)
+      {
+	return ranges::swap_ranges(ranges::begin(__r1), ranges::end(__r1),
+				   ranges::begin(__r2), ranges::end(__r2));
+      }
+
 } // namespace ranges
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
diff --git a/libstdc++-v3/testsuite/25_algorithms/swap_ranges/constrained.cc b/libstdc++-v3/testsuite/25_algorithms/swap_ranges/constrained.cc
new file mode 100644
index 0000000..c44c97d
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/swap_ranges/constrained.cc
@@ -0,0 +1,122 @@
+// 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::input_iterator_wrapper;
+using __gnu_test::forward_iterator_wrapper;
+using __gnu_test::bidirectional_iterator_wrapper;
+
+namespace ranges = std::ranges;
+
+struct X
+{
+  int i;
+  int moved = 0;
+
+  constexpr X(int a) : i(a) { }
+
+  constexpr X(const X&) = delete;
+  constexpr X& operator=(const X&) = delete;
+
+  constexpr X(X&& other)
+  {
+    *this = std::move(other);
+  }
+
+  constexpr X&
+  operator=(X&& other)
+  {
+    other.moved++;
+    i = other.i;
+    return *this;
+  }
+
+  friend constexpr bool
+  operator==(const X& a, const X& b)
+  { return a.i == b.i; }
+};
+
+void
+test01()
+{
+    {
+      X x[7] = { 1, 2, 3, 4, 5, 6, 7 };
+      X y[7] = { 2, 4, 3, 5, 8, 9, 1 };
+      X z[7] = { 1, 2, 3, 4, 5, 6, 7 };
+      X w[7] = { 2, 4, 3, 5, 8, 9, 1 };
+      auto [x_iter, y_iter] = ranges::swap_ranges(x, y);
+      VERIFY( ranges::equal(y, z) && x_iter == x+7 && y_iter == y+7 );
+      VERIFY( ranges::equal(x, w) );
+    }
+
+    {
+      int x[3] = { 1, 2, 3 };
+      int y[4] = { 2, 4, 6, 0 };
+      int z[3] = { 1, 2, 3 };
+      int w[3] = { 2, 4, 6 };
+      test_container<int, forward_iterator_wrapper> cx(x);
+      test_container<int, forward_iterator_wrapper> cy(y);
+      auto [x_iter, y_iter] = ranges::swap_ranges(x, y);
+      VERIFY( ranges::equal(y, y+3, z, z+3) && x_iter == x+3 && y_iter == y+3 );
+      VERIFY( y[3] == 0 );
+      VERIFY( ranges::equal(x, w) );
+    }
+
+    {
+      int x[3] = { 1, 2, 3 };
+      int y[4] = { 2, 4, 6, 0 };
+      int z[3] = { 1, 2, 3 };
+      int w[3] = { 2, 4, 6 };
+      test_range<int, input_iterator_wrapper> cx(x);
+      test_range<int, input_iterator_wrapper> cy(y);
+      auto [y_iter, x_iter] = ranges::swap_ranges(y, x);
+      VERIFY( ranges::equal(y, y+3, z, z+3) && x_iter == x+3 && y_iter == y+3 );
+      VERIFY( y[3] == 0 );
+      VERIFY( ranges::equal(x, w) );
+    }
+}
+
+constexpr bool
+test02()
+{
+  bool ok = true;
+  X x[7] = { 1, 2, 3, 4, 5, 6, 7 };
+  X y[7] = { 2, 4, 3, 5, 8, 9, 1 };
+  X z[7] = { 1, 2, 3, 4, 5, 6, 7 };
+  X w[7] = { 2, 4, 3, 5, 8, 9, 1 };
+  auto [x_iter, y_iter] = ranges::swap_ranges(x, y);
+  ok &= ranges::equal(y, z) && x_iter == x+7 && y_iter == y+7;
+  ok &= ranges::equal(x, w);
+  return ok;
+}
+
+int
+main()
+{
+  test01();
+  static_assert(test02());
+}
+
+