[libc++][ranges] Implement ranges::is_permutation

Co-authored-by: Konstantin Varlamov <[email protected]>

Differential Revision: https://reviews.llvm.org/D127194

Author: philnik777

libcxx/docs/Status/RangesAlgorithms.csv

@@ -33,7 +33,7 @@ Read-only,includes,Hui Xie,`D130116 <https://llvm.org/D130116>`_,✅
 Read-only,is_heap,Konstantin Varlamov,`D130547 <https://llvm.org/D130547>`_,✅
 Read-only,is_heap_until,Konstantin Varlamov,`D130547 <https://llvm.org/D130547>`_,✅
 Read-only,clamp,Nikolas Klauser,`D126193 <https://llvm.org/D126193>`_,✅
-Read-only,is_permutation,Nikolas Klauser,`D127194 <https://llvm.org/D127194>`_,Under review
+Read-only,is_permutation,Nikolas Klauser,`D127194 <https://llvm.org/D127194>`_,✅
 Read-only,for_each,Nikolas Klauser,`D124332 <https://llvm.org/D124332>`_,✅
 Read-only,for_each_n,Nikolas Klauser,`D124332 <https://llvm.org/D124332>`_,✅
 Write,copy,Nikolas Klauser,`D122982 <https://llvm.org/D122982>`_,✅

libcxx/include/CMakeLists.txt

@@ -97,6 +97,7 @@ set(files
   __algorithm/ranges_is_heap.h
   __algorithm/ranges_is_heap_until.h
   __algorithm/ranges_is_partitioned.h
+  __algorithm/ranges_is_permutation.h
   __algorithm/ranges_is_sorted.h
   __algorithm/ranges_is_sorted_until.h
   __algorithm/ranges_iterator_concept.h

libcxx/include/__algorithm/is_permutation.h

@@ -11,151 +11,228 @@
 #define _LIBCPP___ALGORITHM_IS_PERMUTATION_H
 
 #include <__algorithm/comp.h>
+#include <__algorithm/iterator_operations.h>
 #include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__iterator/concepts.h>
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.h>
+#include <__utility/move.h>
+#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
-_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
-is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
-               _BinaryPredicate __pred) {
-  //  shorten sequences as much as possible by lopping of any equal prefix
-  for (; __first1 != __last1; ++__first1, (void)++__first2)
-    if (!__pred(*__first1, *__first2))
-      break;
-  if (__first1 == __last1)
-    return true;
+template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class = void>
+struct _ConstTimeDistance : false_type {};
 
-  //  __first1 != __last1 && *__first1 != *__first2
-  typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
-  _D1 __l1 = _VSTD::distance(__first1, __last1);
-  if (__l1 == _D1(1))
-    return false;
-  _ForwardIterator2 __last2 = _VSTD::next(__first2, __l1);
-  // For each element in [f1, l1) see if there are the same number of
-  //    equal elements in [f2, l2)
-  for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i) {
+#if _LIBCPP_STD_VER > 17
+
+template <class _Iter1, class _Sent1, class _Iter2, class _Sent2>
+struct _ConstTimeDistance<_Iter1, _Sent1, _Iter2, _Sent2, __enable_if_t<
+  sized_sentinel_for<_Sent1, _Iter1> &&
+  sized_sentinel_for<_Sent2, _Iter2>
+>> : true_type {};
+
+#else
+
+template <class _Iter1, class _Iter2>
+struct _ConstTimeDistance<_Iter1, _Iter1, _Iter2, _Iter2, __enable_if_t<
+    is_same<typename iterator_traits<_Iter1>::iterator_category, random_access_iterator_tag>::value &&
+    is_same<typename iterator_traits<_Iter2>::iterator_category, random_access_iterator_tag>::value
+> > : true_type {};
+
+#endif // _LIBCPP_STD_VER > 17
+
+// Internal functions
+
+// For each element in [f1, l1) see if there are the same number of equal elements in [f2, l2)
+template <class _AlgPolicy,
+          class _Iter1, class _Sent1, class _Iter2, class _Sent2,
+          class _Proj1, class _Proj2, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+__is_permutation_impl(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
+                      _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2) {
+  using _D1 = __iter_diff_t<_Iter1>;
+
+  for (auto __i = __first1; __i != __last1; ++__i) {
     //  Have we already counted the number of *__i in [f1, l1)?
-    _ForwardIterator1 __match = __first1;
-    for (; __match != __i; ++__match)
-      if (__pred(*__match, *__i))
+    auto __match = __first1;
+    for (; __match != __i; ++__match) {
+      if (std::__invoke(__pred, std::__invoke(__proj1, *__match), std::__invoke(__proj1, *__i)))
         break;
+    }
+
     if (__match == __i) {
       // Count number of *__i in [f2, l2)
       _D1 __c2 = 0;
-      for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
-        if (__pred(*__i, *__j))
+      for (auto __j = __first2; __j != __last2; ++__j) {
+        if (std::__invoke(__pred, std::__invoke(__proj1, *__i), std::__invoke(__proj2, *__j)))
           ++__c2;
+      }
       if (__c2 == 0)
         return false;
+
       // Count number of *__i in [__i, l1) (we can start with 1)
       _D1 __c1 = 1;
-      for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
-        if (__pred(*__i, *__j))
+      for (auto __j = _IterOps<_AlgPolicy>::next(__i); __j != __last1; ++__j) {
+        if (std::__invoke(__pred, std::__invoke(__proj1, *__i), std::__invoke(__proj1, *__j)))
           ++__c1;
+      }
       if (__c1 != __c2)
         return false;
     }
   }
+
   return true;
 }
 
-template <class _ForwardIterator1, class _ForwardIterator2>
-_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
-is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
-  typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
-  typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
-  return _VSTD::is_permutation(__first1, __last1, __first2, __equal_to<__v1, __v2>());
+// 2+1 iterators, predicate. Not used by range algorithms.
+template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2, class _BinaryPredicate>
+_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+__is_permutation(_ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2,
+                 _BinaryPredicate&& __pred) {
+  // Shorten sequences as much as possible by lopping of any equal prefix.
+  for (; __first1 != __last1; ++__first1, (void)++__first2) {
+    if (!__pred(*__first1, *__first2))
+      break;
+  }
+
+  if (__first1 == __last1)
+    return true;
+
+  //  __first1 != __last1 && *__first1 != *__first2
+  using _D1 = __iter_diff_t<_ForwardIterator1>;
+  _D1 __l1 = _IterOps<_AlgPolicy>::distance(__first1, __last1);
+  if (__l1 == _D1(1))
+    return false;
+  auto __last2 = _IterOps<_AlgPolicy>::next(__first2, __l1);
+
+  return std::__is_permutation_impl<_AlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
+      __pred, __identity(), __identity());
 }
 
-#if _LIBCPP_STD_VER > 11
-template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
-_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
-__is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
-                 _ForwardIterator2 __last2, _BinaryPredicate __pred, forward_iterator_tag, forward_iterator_tag) {
-  //  shorten sequences as much as possible by lopping of any equal prefix
-  for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void)++__first2)
-    if (!__pred(*__first1, *__first2))
+// 2+2 iterators, predicate, non-constant time `distance`.
+template <class _AlgPolicy,
+          class _Iter1, class _Sent1, class _Iter2, class _Sent2,
+          class _Proj1, class _Proj2, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+__is_permutation(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
+                 _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2,
+                 /*_ConstTimeDistance=*/false_type) {
+  // Shorten sequences as much as possible by lopping of any equal prefix.
+  while (__first1 != __last1 && __first2 != __last2) {
+    if (!std::__invoke(__pred, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
       break;
+    ++__first1;
+    ++__first2;
+  }
+
   if (__first1 == __last1)
     return __first2 == __last2;
-  else if (__first2 == __last2)
+  if (__first2 == __last2) // Second range is shorter
     return false;
 
-  typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
-  _D1 __l1 = _VSTD::distance(__first1, __last1);
+  using _D1 = __iter_diff_t<_Iter1>;
+  _D1 __l1 = _IterOps<_AlgPolicy>::distance(__first1, __last1);
 
-  typedef typename iterator_traits<_ForwardIterator2>::difference_type _D2;
-  _D2 __l2 = _VSTD::distance(__first2, __last2);
+  using _D2 = __iter_diff_t<_Iter2>;
+  _D2 __l2 = _IterOps<_AlgPolicy>::distance(__first2, __last2);
   if (__l1 != __l2)
     return false;
 
-  // For each element in [f1, l1) see if there are the same number of
-  //    equal elements in [f2, l2)
-  for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i) {
-    //  Have we already counted the number of *__i in [f1, l1)?
-    _ForwardIterator1 __match = __first1;
-    for (; __match != __i; ++__match)
-      if (__pred(*__match, *__i))
-        break;
-    if (__match == __i) {
-      // Count number of *__i in [f2, l2)
-      _D1 __c2 = 0;
-      for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
-        if (__pred(*__i, *__j))
-          ++__c2;
-      if (__c2 == 0)
-        return false;
-      // Count number of *__i in [__i, l1) (we can start with 1)
-      _D1 __c1 = 1;
-      for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
-        if (__pred(*__i, *__j))
-          ++__c1;
-      if (__c1 != __c2)
-        return false;
-    }
-  }
-  return true;
+  return std::__is_permutation_impl<_AlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
+      __pred, __proj1, __proj2);
 }
 
-template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
-_LIBCPP_CONSTEXPR_AFTER_CXX17 bool __is_permutation(_RandomAccessIterator1 __first1, _RandomAccessIterator2 __last1,
-                                                    _RandomAccessIterator1 __first2, _RandomAccessIterator2 __last2,
-                                                    _BinaryPredicate __pred, random_access_iterator_tag,
-                                                    random_access_iterator_tag) {
-  if (_VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
+// 2+2 iterators, predicate, specialization for constant-time `distance` call.
+template <class _AlgPolicy,
+          class _Iter1, class _Sent1, class _Iter2, class _Sent2,
+          class _Proj1, class _Proj2, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+__is_permutation(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
+                 _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2,
+                 /*_ConstTimeDistance=*/true_type) {
+  if (std::distance(__first1, __last1) != std::distance(__first2, __last2))
     return false;
-  return _VSTD::is_permutation<_RandomAccessIterator1, _RandomAccessIterator2,
-                               _BinaryPredicate&>(__first1, __last1, __first2, __pred);
+  return std::__is_permutation<_AlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
+      __pred, __proj1, __proj2,
+      /*_ConstTimeDistance=*/false_type());
+}
+
+// 2+2 iterators, predicate
+template <class _AlgPolicy,
+          class _Iter1, class _Sent1, class _Iter2, class _Sent2,
+          class _Proj1, class _Proj2, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+__is_permutation(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
+                 _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2) {
+  return std::__is_permutation<_AlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
+      __pred, __proj1, __proj2,
+      _ConstTimeDistance<_Iter1, _Sent1, _Iter2, _Sent2>());
 }
 
+// Public interface
+
+// 2+1 iterators, predicate
 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
-_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
-               _ForwardIterator2 __last2, _BinaryPredicate __pred) {
-  return _VSTD::__is_permutation<_BinaryPredicate&>(
-      __first1, __last1, __first2, __last2, __pred, typename iterator_traits<_ForwardIterator1>::iterator_category(),
-      typename iterator_traits<_ForwardIterator2>::iterator_category());
+               _BinaryPredicate __pred) {
+  static_assert(__is_callable<_BinaryPredicate, decltype(*__first1), decltype(*__first2)>::value,
+      "The predicate has to be callable");
+
+  return std::__is_permutation<_ClassicAlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), __pred);
 }
 
+// 2+1 iterators
+template <class _ForwardIterator1, class _ForwardIterator2>
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
+  using __v1 = __iter_value_type<_ForwardIterator1>;
+  using __v2 = __iter_value_type<_ForwardIterator2>;
+  return std::is_permutation(__first1, __last1, __first2, __equal_to<__v1, __v2>());
+}
+
+#if _LIBCPP_STD_VER > 11
+
+// 2+2 iterators
 template <class _ForwardIterator1, class _ForwardIterator2>
-_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
                _ForwardIterator2 __last2) {
-  typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
-  typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
-  return _VSTD::__is_permutation(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>(),
-                                 typename iterator_traits<_ForwardIterator1>::iterator_category(),
-                                 typename iterator_traits<_ForwardIterator2>::iterator_category());
+  using __v1 = __iter_value_type<_ForwardIterator1>;
+  using __v2 = __iter_value_type<_ForwardIterator2>;
+
+  return std::__is_permutation<_ClassicAlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
+      __equal_to<__v1, __v2>(), __identity(), __identity());
 }
-#endif
+
+// 2+2 iterators, predicate
+template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
+is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
+               _ForwardIterator2 __last2, _BinaryPredicate __pred) {
+  static_assert(__is_callable<_BinaryPredicate, decltype(*__first1), decltype(*__first2)>::value,
+      "The predicate has to be callable");
+
+  return std::__is_permutation<_ClassicAlgPolicy>(
+      std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
+      __pred, __identity(), __identity());
+}
+
+#endif // _LIBCPP_STD_VER > 11
 
 _LIBCPP_END_NAMESPACE_STD