// -*- 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_HASH_SET
#define _LIBCPP_HASH_SET

/*

    hash_set synopsis

namespace __gnu_cxx
{

template <class Value, class Hash = hash<Value>, class Pred = equal_to<Value>,
          class Alloc = allocator<Value>>
class hash_set
{
public:
    // types
    typedef Value                                                      key_type;
    typedef key_type                                                   value_type;
    typedef Hash                                                       hasher;
    typedef Pred                                                       key_equal;
    typedef Alloc                                                      allocator_type;
    typedef value_type&                                                reference;
    typedef const value_type&                                          const_reference;
    typedef typename allocator_traits<allocator_type>::pointer         pointer;
    typedef typename allocator_traits<allocator_type>::const_pointer   const_pointer;
    typedef typename allocator_traits<allocator_type>::size_type       size_type;
    typedef typename allocator_traits<allocator_type>::difference_type difference_type;

    typedef /unspecified/ iterator;
    typedef /unspecified/ const_iterator;

    explicit hash_set(size_type n = 193, const hasher& hf = hasher(),
                           const key_equal& eql = key_equal(),
                           const allocator_type& a = allocator_type());
    template <class InputIterator>
        hash_set(InputIterator f, InputIterator l,
                      size_type n = 193, const hasher& hf = hasher(),
                      const key_equal& eql = key_equal(),
                      const allocator_type& a = allocator_type());
    hash_set(const hash_set&);
    ~hash_set();
    hash_set& operator=(const hash_set&);

    allocator_type get_allocator() const;

    bool      empty() const;
    size_type size() const;
    size_type max_size() const;

    iterator       begin();
    iterator       end();
    const_iterator begin()  const;
    const_iterator end()    const;

    pair<iterator, bool> insert(const value_type& obj);
    template <class InputIterator>
        void insert(InputIterator first, InputIterator last);

    void erase(const_iterator position);
    size_type erase(const key_type& k);
    void erase(const_iterator first, const_iterator last);
    void clear();

    void swap(hash_set&);

    hasher hash_funct() const;
    key_equal key_eq() const;

    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    pair<iterator, iterator>             equal_range(const key_type& k);
    pair<const_iterator, const_iterator> equal_range(const key_type& k) const;

    size_type bucket_count() const;
    size_type max_bucket_count() const;

    size_type elems_in_bucket(size_type n) const;

    void resize(size_type n);
};

template <class Value, class Hash, class Pred, class Alloc>
    void swap(hash_set<Value, Hash, Pred, Alloc>& x,
              hash_set<Value, Hash, Pred, Alloc>& y);

template <class Value, class Hash, class Pred, class Alloc>
    bool
    operator==(const hash_set<Value, Hash, Pred, Alloc>& x,
               const hash_set<Value, Hash, Pred, Alloc>& y);

template <class Value, class Hash, class Pred, class Alloc>
    bool
    operator!=(const hash_set<Value, Hash, Pred, Alloc>& x,
               const hash_set<Value, Hash, Pred, Alloc>& y);

template <class Value, class Hash = hash<Value>, class Pred = equal_to<Value>,
          class Alloc = allocator<Value>>
class hash_multiset
{
public:
    // types
    typedef Value                                                      key_type;
    typedef key_type                                                   value_type;
    typedef Hash                                                       hasher;
    typedef Pred                                                       key_equal;
    typedef Alloc                                                      allocator_type;
    typedef value_type&                                                reference;
    typedef const value_type&                                          const_reference;
    typedef typename allocator_traits<allocator_type>::pointer         pointer;
    typedef typename allocator_traits<allocator_type>::const_pointer   const_pointer;
    typedef typename allocator_traits<allocator_type>::size_type       size_type;
    typedef typename allocator_traits<allocator_type>::difference_type difference_type;

    typedef /unspecified/ iterator;
    typedef /unspecified/ const_iterator;

    explicit hash_multiset(size_type n = 193, const hasher& hf = hasher(),
                           const key_equal& eql = key_equal(),
                           const allocator_type& a = allocator_type());
    template <class InputIterator>
        hash_multiset(InputIterator f, InputIterator l,
                      size_type n = 193, const hasher& hf = hasher(),
                      const key_equal& eql = key_equal(),
                      const allocator_type& a = allocator_type());
    hash_multiset(const hash_multiset&);
    ~hash_multiset();
    hash_multiset& operator=(const hash_multiset&);

    allocator_type get_allocator() const;

    bool      empty() const;
    size_type size() const;
    size_type max_size() const;

    iterator       begin();
    iterator       end();
    const_iterator begin()  const;
    const_iterator end()    const;

    iterator insert(const value_type& obj);
    template <class InputIterator>
        void insert(InputIterator first, InputIterator last);

    void erase(const_iterator position);
    size_type erase(const key_type& k);
    void erase(const_iterator first, const_iterator last);
    void clear();

    void swap(hash_multiset&);

    hasher hash_funct() const;
    key_equal key_eq() const;

    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    pair<iterator, iterator>             equal_range(const key_type& k);
    pair<const_iterator, const_iterator> equal_range(const key_type& k) const;

    size_type bucket_count() const;
    size_type max_bucket_count() const;

    size_type elems_in_bucket(size_type n) const;

    void resize(size_type n);
};

template <class Value, class Hash, class Pred, class Alloc>
    void swap(hash_multiset<Value, Hash, Pred, Alloc>& x,
              hash_multiset<Value, Hash, Pred, Alloc>& y);

template <class Value, class Hash, class Pred, class Alloc>
    bool
    operator==(const hash_multiset<Value, Hash, Pred, Alloc>& x,
               const hash_multiset<Value, Hash, Pred, Alloc>& y);

template <class Value, class Hash, class Pred, class Alloc>
    bool
    operator!=(const hash_multiset<Value, Hash, Pred, Alloc>& x,
               const hash_multiset<Value, Hash, Pred, Alloc>& y);
}  // __gnu_cxx

*/

#include <__config>
#include <__hash_table>
#include <ext/__hash>
#include <functional>

#if defined(__DEPRECATED) && __DEPRECATED
#if defined(_LIBCPP_WARNING)
    _LIBCPP_WARNING("Use of the header <ext/hash_set> is deprecated.  Migrate to <unordered_set>")
#else
#   warning Use of the header <ext/hash_set> is deprecated.  Migrate to <unordered_set>
#endif
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

namespace __gnu_cxx {


template <class _Value, class _Hash = hash<_Value>, class _Pred = std::equal_to<_Value>,
          class _Alloc = std::allocator<_Value> >
class _LIBCPP_TEMPLATE_VIS hash_set
{
public:
    // types
    typedef _Value                                                     key_type;
    typedef key_type                                                   value_type;
    typedef _Hash                                                      hasher;
    typedef _Pred                                                      key_equal;
    typedef _Alloc                                                     allocator_type;
    typedef value_type&                                                reference;
    typedef const value_type&                                          const_reference;

private:
    typedef std::__hash_table<value_type, hasher, key_equal, allocator_type> __table;

    __table __table_;

public:
    typedef typename __table::pointer         pointer;
    typedef typename __table::const_pointer   const_pointer;
    typedef typename __table::size_type       size_type;
    typedef typename __table::difference_type difference_type;

    typedef typename __table::const_iterator       iterator;
    typedef typename __table::const_iterator       const_iterator;

    _LIBCPP_INLINE_VISIBILITY
    hash_set() { }
    explicit hash_set(size_type __n, const hasher& __hf = hasher(),
                           const key_equal& __eql = key_equal());
    hash_set(size_type __n, const hasher& __hf, const key_equal& __eql,
                  const allocator_type& __a);
    template <class _InputIterator>
        hash_set(_InputIterator __first, _InputIterator __last);
    template <class _InputIterator>
        hash_set(_InputIterator __first, _InputIterator __last,
                      size_type __n, const hasher& __hf = hasher(),
                      const key_equal& __eql = key_equal());
    template <class _InputIterator>
        hash_set(_InputIterator __first, _InputIterator __last,
                      size_type __n, const hasher& __hf, const key_equal& __eql,
                      const allocator_type& __a);
    hash_set(const hash_set& __u);

    _LIBCPP_INLINE_VISIBILITY
    allocator_type get_allocator() const
        {return allocator_type(__table_.__node_alloc());}

    _LIBCPP_INLINE_VISIBILITY
    bool      empty() const {return __table_.size() == 0;}
    _LIBCPP_INLINE_VISIBILITY
    size_type size() const  {return __table_.size();}
    _LIBCPP_INLINE_VISIBILITY
    size_type max_size() const {return __table_.max_size();}

    _LIBCPP_INLINE_VISIBILITY
    iterator       begin()        {return __table_.begin();}
    _LIBCPP_INLINE_VISIBILITY
    iterator       end()          {return __table_.end();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator begin()  const {return __table_.begin();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator end()    const {return __table_.end();}

    _LIBCPP_INLINE_VISIBILITY
    std::pair<iterator, bool> insert(const value_type& __x)
        {return __table_.__insert_unique(__x);}
    _LIBCPP_INLINE_VISIBILITY
    iterator insert(const_iterator, const value_type& __x) {return insert(__x).first;}
    template <class _InputIterator>
        _LIBCPP_INLINE_VISIBILITY
        void insert(_InputIterator __first, _InputIterator __last);

    _LIBCPP_INLINE_VISIBILITY
    void erase(const_iterator __p) {__table_.erase(__p);}
    _LIBCPP_INLINE_VISIBILITY
    size_type erase(const key_type& __k) {return __table_.__erase_unique(__k);}
    _LIBCPP_INLINE_VISIBILITY
    void erase(const_iterator __first, const_iterator __last)
        {__table_.erase(__first, __last);}
    _LIBCPP_INLINE_VISIBILITY
    void clear() {__table_.clear();}

    _LIBCPP_INLINE_VISIBILITY
    void swap(hash_set& __u) {__table_.swap(__u.__table_);}

    _LIBCPP_INLINE_VISIBILITY
    hasher hash_funct() const {return __table_.hash_function();}
    _LIBCPP_INLINE_VISIBILITY
    key_equal key_eq() const {return __table_.key_eq();}

    _LIBCPP_INLINE_VISIBILITY
    iterator       find(const key_type& __k)       {return __table_.find(__k);}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator find(const key_type& __k) const {return __table_.find(__k);}
    _LIBCPP_INLINE_VISIBILITY
    size_type count(const key_type& __k) const {return __table_.__count_unique(__k);}
    _LIBCPP_INLINE_VISIBILITY
    std::pair<iterator, iterator>             equal_range(const key_type& __k)
        {return __table_.__equal_range_unique(__k);}
    _LIBCPP_INLINE_VISIBILITY
    std::pair<const_iterator, const_iterator> equal_range(const key_type& __k) const
        {return __table_.__equal_range_unique(__k);}

    _LIBCPP_INLINE_VISIBILITY
    size_type bucket_count() const {return __table_.bucket_count();}
    _LIBCPP_INLINE_VISIBILITY
    size_type max_bucket_count() const {return __table_.max_bucket_count();}

    _LIBCPP_INLINE_VISIBILITY
    size_type elems_in_bucket(size_type __n) const {return __table_.bucket_size(__n);}

    _LIBCPP_INLINE_VISIBILITY
    void resize(size_type __n) {__table_.rehash(__n);}
};

template <class _Value, class _Hash, class _Pred, class _Alloc>
hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(size_type __n,
        const hasher& __hf, const key_equal& __eql)
    : __table_(__hf, __eql)
{
    __table_.rehash(__n);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(size_type __n,
        const hasher& __hf, const key_equal& __eql, const allocator_type& __a)
    : __table_(__hf, __eql, __a)
{
    __table_.rehash(__n);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(
        _InputIterator __first, _InputIterator __last)
{
    insert(__first, __last);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(
        _InputIterator __first, _InputIterator __last, size_type __n,
        const hasher& __hf, const key_equal& __eql)
    : __table_(__hf, __eql)
{
    __table_.rehash(__n);
    insert(__first, __last);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(
        _InputIterator __first, _InputIterator __last, size_type __n,
        const hasher& __hf, const key_equal& __eql, const allocator_type& __a)
    : __table_(__hf, __eql, __a)
{
    __table_.rehash(__n);
    insert(__first, __last);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(
        const hash_set& __u)
    : __table_(__u.__table_)
{
    __table_.rehash(__u.bucket_count());
    insert(__u.begin(), __u.end());
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
inline
void
hash_set<_Value, _Hash, _Pred, _Alloc>::insert(_InputIterator __first,
                                                    _InputIterator __last)
{
    for (; __first != __last; ++__first)
        __table_.__insert_unique(*__first);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(hash_set<_Value, _Hash, _Pred, _Alloc>& __x,
     hash_set<_Value, _Hash, _Pred, _Alloc>& __y)
{
    __x.swap(__y);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
bool
operator==(const hash_set<_Value, _Hash, _Pred, _Alloc>& __x,
           const hash_set<_Value, _Hash, _Pred, _Alloc>& __y)
{
    if (__x.size() != __y.size())
        return false;
    typedef typename hash_set<_Value, _Hash, _Pred, _Alloc>::const_iterator
                                                                 const_iterator;
    for (const_iterator __i = __x.begin(), __ex = __x.end(), __ey = __y.end();
            __i != __ex; ++__i)
    {
        const_iterator __j = __y.find(*__i);
        if (__j == __ey || !(*__i == *__j))
            return false;
    }
    return true;
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const hash_set<_Value, _Hash, _Pred, _Alloc>& __x,
           const hash_set<_Value, _Hash, _Pred, _Alloc>& __y)
{
    return !(__x == __y);
}

template <class _Value, class _Hash = hash<_Value>, class _Pred = std::equal_to<_Value>,
          class _Alloc = std::allocator<_Value> >
class _LIBCPP_TEMPLATE_VIS hash_multiset
{
public:
    // types
    typedef _Value                                                     key_type;
    typedef key_type                                                   value_type;
    typedef _Hash                                                      hasher;
    typedef _Pred                                                      key_equal;
    typedef _Alloc                                                     allocator_type;
    typedef value_type&                                                reference;
    typedef const value_type&                                          const_reference;

private:
    typedef std::__hash_table<value_type, hasher, key_equal, allocator_type> __table;

    __table __table_;

public:
    typedef typename __table::pointer         pointer;
    typedef typename __table::const_pointer   const_pointer;
    typedef typename __table::size_type       size_type;
    typedef typename __table::difference_type difference_type;

    typedef typename __table::const_iterator       iterator;
    typedef typename __table::const_iterator       const_iterator;

    _LIBCPP_INLINE_VISIBILITY
    hash_multiset() { }
    explicit hash_multiset(size_type __n, const hasher& __hf = hasher(),
                                const key_equal& __eql = key_equal());
    hash_multiset(size_type __n, const hasher& __hf,
                       const key_equal& __eql, const allocator_type& __a);
    template <class _InputIterator>
        hash_multiset(_InputIterator __first, _InputIterator __last);
    template <class _InputIterator>
        hash_multiset(_InputIterator __first, _InputIterator __last,
                      size_type __n, const hasher& __hf = hasher(),
                      const key_equal& __eql = key_equal());
    template <class _InputIterator>
        hash_multiset(_InputIterator __first, _InputIterator __last,
                      size_type __n , const hasher& __hf,
                      const key_equal& __eql, const allocator_type& __a);
    hash_multiset(const hash_multiset& __u);

    _LIBCPP_INLINE_VISIBILITY
    allocator_type get_allocator() const
        {return allocator_type(__table_.__node_alloc());}

    _LIBCPP_INLINE_VISIBILITY
    bool      empty() const {return __table_.size() == 0;}
    _LIBCPP_INLINE_VISIBILITY
    size_type size() const  {return __table_.size();}
    _LIBCPP_INLINE_VISIBILITY
    size_type max_size() const {return __table_.max_size();}

    _LIBCPP_INLINE_VISIBILITY
    iterator       begin()        {return __table_.begin();}
    _LIBCPP_INLINE_VISIBILITY
    iterator       end()          {return __table_.end();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator begin()  const {return __table_.begin();}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator end()    const {return __table_.end();}

    _LIBCPP_INLINE_VISIBILITY
    iterator insert(const value_type& __x) {return __table_.__insert_multi(__x);}
    _LIBCPP_INLINE_VISIBILITY
    iterator insert(const_iterator, const value_type& __x) {return insert(__x);}
    template <class _InputIterator>
        _LIBCPP_INLINE_VISIBILITY
        void insert(_InputIterator __first, _InputIterator __last);

    _LIBCPP_INLINE_VISIBILITY
    void erase(const_iterator __p) {__table_.erase(__p);}
    _LIBCPP_INLINE_VISIBILITY
    size_type erase(const key_type& __k) {return __table_.__erase_multi(__k);}
    _LIBCPP_INLINE_VISIBILITY
    void erase(const_iterator __first, const_iterator __last)
        {__table_.erase(__first, __last);}
    _LIBCPP_INLINE_VISIBILITY
    void clear() {__table_.clear();}

    _LIBCPP_INLINE_VISIBILITY
    void swap(hash_multiset& __u) {__table_.swap(__u.__table_);}

    _LIBCPP_INLINE_VISIBILITY
    hasher hash_funct() const {return __table_.hash_function();}
    _LIBCPP_INLINE_VISIBILITY
    key_equal key_eq() const {return __table_.key_eq();}

    _LIBCPP_INLINE_VISIBILITY
    iterator       find(const key_type& __k)       {return __table_.find(__k);}
    _LIBCPP_INLINE_VISIBILITY
    const_iterator find(const key_type& __k) const {return __table_.find(__k);}
    _LIBCPP_INLINE_VISIBILITY
    size_type count(const key_type& __k) const {return __table_.__count_multi(__k);}
    _LIBCPP_INLINE_VISIBILITY
    std::pair<iterator, iterator>             equal_range(const key_type& __k)
        {return __table_.__equal_range_multi(__k);}
    _LIBCPP_INLINE_VISIBILITY
    std::pair<const_iterator, const_iterator> equal_range(const key_type& __k) const
        {return __table_.__equal_range_multi(__k);}

    _LIBCPP_INLINE_VISIBILITY
    size_type bucket_count() const {return __table_.bucket_count();}
    _LIBCPP_INLINE_VISIBILITY
    size_type max_bucket_count() const {return __table_.max_bucket_count();}

    _LIBCPP_INLINE_VISIBILITY
    size_type elems_in_bucket(size_type __n) const {return __table_.bucket_size(__n);}

    _LIBCPP_INLINE_VISIBILITY
    void resize(size_type __n) {__table_.rehash(__n);}
};

template <class _Value, class _Hash, class _Pred, class _Alloc>
hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
        size_type __n, const hasher& __hf, const key_equal& __eql)
    : __table_(__hf, __eql)
{
    __table_.rehash(__n);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
        size_type __n, const hasher& __hf, const key_equal& __eql,
        const allocator_type& __a)
    : __table_(__hf, __eql, __a)
{
    __table_.rehash(__n);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
        _InputIterator __first, _InputIterator __last)
{
    insert(__first, __last);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
        _InputIterator __first, _InputIterator __last, size_type __n,
        const hasher& __hf, const key_equal& __eql)
    : __table_(__hf, __eql)
{
    __table_.rehash(__n);
    insert(__first, __last);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
        _InputIterator __first, _InputIterator __last, size_type __n,
        const hasher& __hf, const key_equal& __eql, const allocator_type& __a)
    : __table_(__hf, __eql, __a)
{
    __table_.rehash(__n);
    insert(__first, __last);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
        const hash_multiset& __u)
    : __table_(__u.__table_)
{
    __table_.rehash(__u.bucket_count());
    insert(__u.begin(), __u.end());
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
template <class _InputIterator>
inline
void
hash_multiset<_Value, _Hash, _Pred, _Alloc>::insert(_InputIterator __first,
                                                    _InputIterator __last)
{
    for (; __first != __last; ++__first)
        __table_.__insert_multi(*__first);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(hash_multiset<_Value, _Hash, _Pred, _Alloc>& __x,
     hash_multiset<_Value, _Hash, _Pred, _Alloc>& __y)
{
    __x.swap(__y);
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
bool
operator==(const hash_multiset<_Value, _Hash, _Pred, _Alloc>& __x,
           const hash_multiset<_Value, _Hash, _Pred, _Alloc>& __y)
{
    if (__x.size() != __y.size())
        return false;
    typedef typename hash_multiset<_Value, _Hash, _Pred, _Alloc>::const_iterator
                                                                 const_iterator;
    typedef std::pair<const_iterator, const_iterator> _EqRng;
    for (const_iterator __i = __x.begin(), __ex = __x.end(); __i != __ex;)
    {
        _EqRng __xeq = __x.equal_range(*__i);
        _EqRng __yeq = __y.equal_range(*__i);
        if (_VSTD::distance(__xeq.first, __xeq.second) !=
            _VSTD::distance(__yeq.first, __yeq.second) ||
                  !_VSTD::is_permutation(__xeq.first, __xeq.second, __yeq.first))
            return false;
        __i = __xeq.second;
    }
    return true;
}

template <class _Value, class _Hash, class _Pred, class _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const hash_multiset<_Value, _Hash, _Pred, _Alloc>& __x,
           const hash_multiset<_Value, _Hash, _Pred, _Alloc>& __y)
{
    return !(__x == __y);
}

} // namespace __gnu_cxx

#endif // _LIBCPP_HASH_SET