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

[Patrick Palka]

https://gcc.gnu.org/g:2d063a6c086cb11971aeefdff81dcf94a4a84dff

commit 2d063a6c086cb11971aeefdff81dcf94a4a84dff
Author: Patrick Palka <ppalka@gcc.gnu.org>
Date:   Fri Jan 17 14:57:38 2020 -0500

    Add ranges::is_permutation

Diff:
---
 libstdc++-v3/include/bits/ranges_algo.h            | 82 +++++++++++++++++++++
 .../25_algorithms/is_permutation/constrained.cc    | 85 ++++++++++++++++++++++
 2 files changed, 167 insertions(+)

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 8bb9bfa..b41f7d7 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -535,6 +535,88 @@ namespace ranges
 				     std::move(__pred), std::move(__proj));
       }
 
+    template<forward_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
+	     forward_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
+	     class _Proj1 = identity, class _Proj2 = identity,
+	     indirect_equivalence_relation<projected<_Iter1, _Proj1>,
+					   projected<_Iter2, _Proj2>> _Pred
+	       = ranges::equal_to>
+      constexpr bool
+      is_permutation(_Iter1 __first1, _Sent1 __last1,
+		     _Iter2 __first2, _Sent2 __last2, _Pred __pred = {},
+		     _Proj1 __proj1 = {}, _Proj2 __proj2 = {})
+      {
+	constexpr bool __sized_iters
+	  = (std::sized_sentinel_for<_Sent1, _Iter1>
+	     && std::sized_sentinel_for<_Sent2, _Iter2>);
+	if constexpr (__sized_iters)
+	  {
+	    auto __d1 = std::distance(__first1, __last1);
+	    auto __d2 = std::distance(__first2, __last2);
+	    if (__d1 != __d2)
+	      return false;
+	  }
+
+	// Efficiently compare identical prefixes:  O(N) if sequences
+	// have the same elements in the same order.
+	for (; __first1 != __last1 && __first2 != __last2;
+	     ++__first1, (void)++__first2)
+	  if (!std::__invoke(__pred,
+			     std::__invoke(__proj1, *__first1),
+			     std::__invoke(__proj2, *__first2)))
+	      break;
+
+	if constexpr (__sized_iters)
+	  {
+	    if (__first1 == __last1)
+	      return true;
+	  }
+	else
+	  {
+	    auto __d1 = std::distance(__first1, __last1);
+	    auto __d2 = std::distance(__first2, __last2);
+	    if (__d1 == 0 && __d2 == 0)
+	      return true;
+	    if (__d1 != __d2)
+	      return false;
+	  }
+
+	for (auto __scan = __first1; __scan != __last1; ++__scan)
+	  {
+	    auto __proj_scan = std::__invoke(__proj1, *__scan);
+	    auto __comp_scan = [&] <typename _Tp> (_Tp&& __arg) {
+	      return std::__invoke(__pred, __proj_scan,
+				   std::forward<_Tp>(__arg));
+	    };
+	    if (__scan != ranges::find_if(__first1, __scan,
+					  __comp_scan, __proj1))
+	      continue; // We've seen this one before.
+
+	    auto __matches = ranges::count_if(__first2, __last2,
+					      __comp_scan, __proj2);
+	    if (__matches == 0
+		|| ranges::count_if(__scan, __last1,
+				    __comp_scan, __proj1) != __matches)
+	      return false;
+	  }
+	return true;
+      }
+
+    template<forward_range _Range1, forward_range _Range2,
+	     class _Proj1 = identity, class _Proj2 = identity,
+	     indirect_equivalence_relation<
+	       projected<iterator_t<_Range1>, _Proj1>,
+	       projected<iterator_t<_Range2>, _Proj2>> _Pred = ranges::equal_to>
+      constexpr bool
+      is_permutation(_Range1&& __r1, _Range2&& __r2, _Pred __pred = {},
+		     _Proj1 __proj1 = {}, _Proj2 __proj2 = {})
+      {
+	return ranges::is_permutation(ranges::begin(__r1), ranges::end(__r1),
+				      ranges::begin(__r2), ranges::end(__r2),
+				      std::move(__pred),
+				      std::move(__proj1), std::move(__proj2));
+      }
+
 } // namespace ranges
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_permutation/constrained.cc b/libstdc++-v3/testsuite/25_algorithms/is_permutation/constrained.cc
new file mode 100644
index 0000000..c5393be
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/is_permutation/constrained.cc
@@ -0,0 +1,85 @@
+// 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; };
+
+void
+test01()
+{
+  int x[] = { {2}, {2}, {6}, {8}, {10}, {11} };
+  int y[] = { {2}, {6}, {8}, {10}, {11}, {2} };
+  int z[] = { {2}, {6}, {8}, {10}, {2}, {2} };
+
+  VERIFY( ranges::is_permutation(x, x+6, y, y+6) );
+  VERIFY( !ranges::is_permutation(x, x+6, y, y+5) );
+
+  test_container<int, forward_iterator_wrapper> cx(x), cy(y), cz(z);
+  test_range<int, forward_iterator_wrapper> rx(x), ry(y), rz(z);
+  VERIFY( ranges::is_permutation(cx, ry) );
+  VERIFY( !ranges::is_permutation(rx, cz) );
+  VERIFY( ranges::is_permutation(rx, cy) );
+  VERIFY( !ranges::is_permutation(cx, rz) );
+}
+
+void
+test02()
+{
+  static constexpr X x[] = { {2}, {2}, {6}, {8}, {10}, {11} };
+  static constexpr X y[] = { {2}, {6}, {8}, {10}, {11}, {2} };
+  static constexpr int z[] = { {2}, {6}, {8}, {10}, {2}, {2} };
+  static_assert(ranges::is_permutation(x, y, {}, &X::i, &X::i));
+  static_assert(!ranges::is_permutation(x, z, {}, &X::i));
+  static_assert(!ranges::is_permutation(z, y, {}, {}, &X::i));
+}
+
+void
+test03()
+{
+  int x[] = { 1, 2, 3, 4 };
+  int y[] = { 1, 2, 3, 3 };
+  test_container<int, bidirectional_iterator_wrapper> cx(x);
+  do
+    do
+      {
+	VERIFY( ranges::is_permutation(cx, x) );
+	VERIFY( !ranges::is_permutation(y, cx) );
+      } while (std::next_permutation(y, y+4));
+  while (std::next_permutation(std::begin(cx), std::end(cx)));
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+}