xref: /llvm-project-15.0.7/libcxx/include/queue (revision e34f5ffe)

// -*- C++ -*-
//===--------------------------- queue ------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_QUEUE
#define _LIBCPP_QUEUE

/*
    queue synopsis

namespace std
{

template <class T, class Container = deque<T>>
class queue
{
public:
    typedef Container                                container_type;
    typedef typename container_type::value_type      value_type;
    typedef typename container_type::reference       reference;
    typedef typename container_type::const_reference const_reference;
    typedef typename container_type::size_type       size_type;

protected:
    container_type c;

public:
    queue() = default;
    ~queue() = default;

    queue(const queue& q) = default;
    queue(queue&& q) = default;

    queue& operator=(const queue& q) = default;
    queue& operator=(queue&& q) = default;

    explicit queue(const container_type& c);
    explicit queue(container_type&& c)
    template <class Alloc>
        explicit queue(const Alloc& a);
    template <class Alloc>
        queue(const container_type& c, const Alloc& a);
    template <class Alloc>
        queue(container_type&& c, const Alloc& a);
    template <class Alloc>
        queue(const queue& q, const Alloc& a);
    template <class Alloc>
        queue(queue&& q, const Alloc& a);

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

    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    void push(const value_type& v);
    void push(value_type&& v);
    template <class... Args> reference emplace(Args&&... args); // reference in C++17
    void pop();

    void swap(queue& q) noexcept(is_nothrow_swappable_v<Container>)
};

template <class T, class Container>
  bool operator==(const queue<T, Container>& x,const queue<T, Container>& y);

template <class T, class Container>
  bool operator< (const queue<T, Container>& x,const queue<T, Container>& y);

template <class T, class Container>
  bool operator!=(const queue<T, Container>& x,const queue<T, Container>& y);

template <class T, class Container>
  bool operator> (const queue<T, Container>& x,const queue<T, Container>& y);

template <class T, class Container>
  bool operator>=(const queue<T, Container>& x,const queue<T, Container>& y);

template <class T, class Container>
  bool operator<=(const queue<T, Container>& x,const queue<T, Container>& y);

template <class T, class Container>
  void swap(queue<T, Container>& x, queue<T, Container>& y)
  noexcept(noexcept(x.swap(y)));

template <class T, class Container = vector<T>,
          class Compare = less<typename Container::value_type>>
class priority_queue
{
public:
    typedef Container                                container_type;
    typedef typename container_type::value_type      value_type;
    typedef typename container_type::reference       reference;
    typedef typename container_type::const_reference const_reference;
    typedef typename container_type::size_type       size_type;

protected:
    container_type c;
    Compare comp;

public:
    priority_queue() = default;
    ~priority_queue() = default;

    priority_queue(const priority_queue& q) = default;
    priority_queue(priority_queue&& q) = default;

    priority_queue& operator=(const priority_queue& q) = default;
    priority_queue& operator=(priority_queue&& q) = default;

    explicit priority_queue(const Compare& comp);
    priority_queue(const Compare& comp, const container_type& c);
    explicit priority_queue(const Compare& comp, container_type&& c);
    template <class InputIterator>
        priority_queue(InputIterator first, InputIterator last,
                       const Compare& comp = Compare());
    template <class InputIterator>
        priority_queue(InputIterator first, InputIterator last,
                       const Compare& comp, const container_type& c);
    template <class InputIterator>
        priority_queue(InputIterator first, InputIterator last,
                       const Compare& comp, container_type&& c);
    template <class Alloc>
        explicit priority_queue(const Alloc& a);
    template <class Alloc>
        priority_queue(const Compare& comp, const Alloc& a);
    template <class Alloc>
        priority_queue(const Compare& comp, const container_type& c,
                       const Alloc& a);
    template <class Alloc>
        priority_queue(const Compare& comp, container_type&& c,
                       const Alloc& a);
    template <class Alloc>
        priority_queue(const priority_queue& q, const Alloc& a);
    template <class Alloc>
        priority_queue(priority_queue&& q, const Alloc& a);

    bool            empty() const;
    size_type       size() const;
    const_reference top() const;

    void push(const value_type& v);
    void push(value_type&& v);
    template <class... Args> void emplace(Args&&... args);
    void pop();

    void swap(priority_queue& q)
        noexcept(is_nothrow_swappable_v<Container> &&
                 is_nothrow_swappable_v<Comp>)
};

template <class T, class Container, class Compare>
  void swap(priority_queue<T, Container, Compare>& x,
            priority_queue<T, Container, Compare>& y)
            noexcept(noexcept(x.swap(y)));

}  // std

*/

#include <__config>
#include <deque>
#include <vector>
#include <functional>
#include <algorithm>

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

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Tp, class _Container = deque<_Tp> > class _LIBCPP_TEMPLATE_VIS queue;

template <class _Tp, class _Container>
_LIBCPP_INLINE_VISIBILITY
bool
operator==(const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y);

template <class _Tp, class _Container>
_LIBCPP_INLINE_VISIBILITY
bool
operator< (const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y);

template <class _Tp, class _Container /*= deque<_Tp>*/>
class _LIBCPP_TEMPLATE_VIS queue
{
public:
    typedef _Container                               container_type;
    typedef typename container_type::value_type      value_type;
    typedef typename container_type::reference       reference;
    typedef typename container_type::const_reference const_reference;
    typedef typename container_type::size_type       size_type;
    static_assert((is_same<_Tp, value_type>::value), "" );

protected:
    container_type c;

public:
    _LIBCPP_INLINE_VISIBILITY
    queue()
        _NOEXCEPT_(is_nothrow_default_constructible<container_type>::value)
        : c() {}

    _LIBCPP_INLINE_VISIBILITY
    queue(const queue& __q) : c(__q.c) {}

    _LIBCPP_INLINE_VISIBILITY
    queue& operator=(const queue& __q) {c = __q.c; return *this;}

#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    queue(queue&& __q)
        _NOEXCEPT_(is_nothrow_move_constructible<container_type>::value)
        : c(_VSTD::move(__q.c)) {}

    _LIBCPP_INLINE_VISIBILITY
    queue& operator=(queue&& __q)
        _NOEXCEPT_(is_nothrow_move_assignable<container_type>::value)
        {c = _VSTD::move(__q.c); return *this;}
#endif  // _LIBCPP_CXX03_LANG

    _LIBCPP_INLINE_VISIBILITY
    explicit queue(const container_type& __c)  : c(__c) {}
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    explicit queue(container_type&& __c) : c(_VSTD::move(__c)) {}
#endif  // _LIBCPP_CXX03_LANG
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        explicit queue(const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0)
            : c(__a) {}
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        queue(const queue& __q, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0)
            : c(__q.c, __a) {}
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        queue(const container_type& __c, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0)
            : c(__c, __a) {}
#ifndef _LIBCPP_CXX03_LANG
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        queue(container_type&& __c, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0)
            : c(_VSTD::move(__c), __a) {}
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        queue(queue&& __q, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0)
            : c(_VSTD::move(__q.c), __a) {}

#endif  // _LIBCPP_CXX03_LANG

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
    bool      empty() const {return c.empty();}
    _LIBCPP_INLINE_VISIBILITY
    size_type size() const  {return c.size();}

    _LIBCPP_INLINE_VISIBILITY
    reference       front()       {return c.front();}
    _LIBCPP_INLINE_VISIBILITY
    const_reference front() const {return c.front();}
    _LIBCPP_INLINE_VISIBILITY
    reference       back()        {return c.back();}
    _LIBCPP_INLINE_VISIBILITY
    const_reference back() const  {return c.back();}

    _LIBCPP_INLINE_VISIBILITY
    void push(const value_type& __v) {c.push_back(__v);}
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    void push(value_type&& __v)      {c.push_back(_VSTD::move(__v));}
    template <class... _Args>
        _LIBCPP_INLINE_VISIBILITY
#if _LIBCPP_STD_VER > 14
        decltype(auto) emplace(_Args&&... __args)
            { return c.emplace_back(_VSTD::forward<_Args>(__args)...);}
#else
        void     emplace(_Args&&... __args)
            {        c.emplace_back(_VSTD::forward<_Args>(__args)...);}
#endif
#endif  // _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    void pop() {c.pop_front();}

    _LIBCPP_INLINE_VISIBILITY
    void swap(queue& __q)
        _NOEXCEPT_(__is_nothrow_swappable<container_type>::value)
    {
        using _VSTD::swap;
        swap(c, __q.c);
    }

    template <class _T1, class _C1>
    friend
    _LIBCPP_INLINE_VISIBILITY
    bool
    operator==(const queue<_T1, _C1>& __x,const queue<_T1, _C1>& __y);

    template <class _T1, class _C1>
    friend
    _LIBCPP_INLINE_VISIBILITY
    bool
    operator< (const queue<_T1, _C1>& __x,const queue<_T1, _C1>& __y);
};

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y)
{
    return __x.c == __y.c;
}

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator< (const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y)
{
    return __x.c < __y.c;
}

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y)
{
    return !(__x == __y);
}

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator> (const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y)
{
    return __y < __x;
}

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y)
{
    return !(__x < __y);
}

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y)
{
    return !(__y < __x);
}

template <class _Tp, class _Container>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if<
    __is_swappable<_Container>::value,
    void
>::type
swap(queue<_Tp, _Container>& __x, queue<_Tp, _Container>& __y)
    _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y)))
{
    __x.swap(__y);
}

template <class _Tp, class _Container, class _Alloc>
struct _LIBCPP_TEMPLATE_VIS uses_allocator<queue<_Tp, _Container>, _Alloc>
    : public uses_allocator<_Container, _Alloc>
{
};

template <class _Tp, class _Container = vector<_Tp>,
          class _Compare = less<typename _Container::value_type> >
class _LIBCPP_TEMPLATE_VIS priority_queue
{
public:
    typedef _Container                               container_type;
    typedef _Compare                                 value_compare;
    typedef typename container_type::value_type      value_type;
    typedef typename container_type::reference       reference;
    typedef typename container_type::const_reference const_reference;
    typedef typename container_type::size_type       size_type;
    static_assert((is_same<_Tp, value_type>::value), "" );

protected:
    container_type c;
    value_compare comp;

public:
    _LIBCPP_INLINE_VISIBILITY
    priority_queue()
        _NOEXCEPT_(is_nothrow_default_constructible<container_type>::value &&
                   is_nothrow_default_constructible<value_compare>::value)
        : c(), comp() {}

    _LIBCPP_INLINE_VISIBILITY
    priority_queue(const priority_queue& __q) : c(__q.c), comp(__q.comp) {}

    _LIBCPP_INLINE_VISIBILITY
    priority_queue& operator=(const priority_queue& __q)
        {c = __q.c; comp = __q.comp; return *this;}

#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    priority_queue(priority_queue&& __q)
        _NOEXCEPT_(is_nothrow_move_constructible<container_type>::value &&
                   is_nothrow_move_constructible<value_compare>::value)
        : c(_VSTD::move(__q.c)), comp(_VSTD::move(__q.comp)) {}

    _LIBCPP_INLINE_VISIBILITY
    priority_queue& operator=(priority_queue&& __q)
        _NOEXCEPT_(is_nothrow_move_assignable<container_type>::value &&
                   is_nothrow_move_assignable<value_compare>::value)
        {c = _VSTD::move(__q.c); comp = _VSTD::move(__q.comp); return *this;}
#endif  // _LIBCPP_CXX03_LANG

    _LIBCPP_INLINE_VISIBILITY
    explicit priority_queue(const value_compare& __comp)
        : c(), comp(__comp) {}
    _LIBCPP_INLINE_VISIBILITY
    priority_queue(const value_compare& __comp, const container_type& __c);
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    explicit priority_queue(const value_compare& __comp, container_type&& __c);
#endif
    template <class _InputIter>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(_InputIter __f, _InputIter __l,
                       const value_compare& __comp = value_compare());
    template <class _InputIter>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(_InputIter __f, _InputIter __l,
                       const value_compare& __comp, const container_type& __c);
#ifndef _LIBCPP_CXX03_LANG
    template <class _InputIter>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(_InputIter __f, _InputIter __l,
                       const value_compare& __comp, container_type&& __c);
#endif  // _LIBCPP_CXX03_LANG
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        explicit priority_queue(const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0);
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(const value_compare& __comp, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0);
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(const value_compare& __comp, const container_type& __c,
                       const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0);
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(const priority_queue& __q, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0);
#ifndef _LIBCPP_CXX03_LANG
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(const value_compare& __comp, container_type&& __c,
                       const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0);
    template <class _Alloc>
        _LIBCPP_INLINE_VISIBILITY
        priority_queue(priority_queue&& __q, const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type* = 0);
#endif  // _LIBCPP_CXX03_LANG

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
    bool            empty() const {return c.empty();}
    _LIBCPP_INLINE_VISIBILITY
    size_type       size() const  {return c.size();}
    _LIBCPP_INLINE_VISIBILITY
    const_reference top() const   {return c.front();}

    _LIBCPP_INLINE_VISIBILITY
    void push(const value_type& __v);
#ifndef _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    void push(value_type&& __v);
    template <class... _Args>
    _LIBCPP_INLINE_VISIBILITY
    void emplace(_Args&&... __args);
#endif  // _LIBCPP_CXX03_LANG
    _LIBCPP_INLINE_VISIBILITY
    void pop();

    _LIBCPP_INLINE_VISIBILITY
    void swap(priority_queue& __q)
        _NOEXCEPT_(__is_nothrow_swappable<container_type>::value &&
                   __is_nothrow_swappable<value_compare>::value);
};

template <class _Tp, class _Container, class _Compare>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const _Compare& __comp,
                                                          const container_type& __c)
    : c(__c),
      comp(__comp)
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

#ifndef _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const value_compare& __comp,
                                                          container_type&& __c)
    : c(_VSTD::move(__c)),
      comp(__comp)
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

#endif  // _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
template <class _InputIter>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(_InputIter __f, _InputIter __l,
                                                          const value_compare& __comp)
    : c(__f, __l),
      comp(__comp)
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

template <class _Tp, class _Container, class _Compare>
template <class _InputIter>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(_InputIter __f, _InputIter __l,
                                                          const value_compare& __comp,
                                                          const container_type& __c)
    : c(__c),
      comp(__comp)
{
    c.insert(c.end(), __f, __l);
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

#ifndef _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
template <class _InputIter>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(_InputIter __f, _InputIter __l,
                                                          const value_compare& __comp,
                                                          container_type&& __c)
    : c(_VSTD::move(__c)),
      comp(__comp)
{
    c.insert(c.end(), __f, __l);
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

#endif  // _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
template <class _Alloc>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type*)
    : c(__a)
{
}

template <class _Tp, class _Container, class _Compare>
template <class _Alloc>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const value_compare& __comp,
                                                          const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type*)
    : c(__a),
      comp(__comp)
{
}

template <class _Tp, class _Container, class _Compare>
template <class _Alloc>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const value_compare& __comp,
                                                          const container_type& __c,
                                                          const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type*)
    : c(__c, __a),
      comp(__comp)
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

template <class _Tp, class _Container, class _Compare>
template <class _Alloc>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const priority_queue& __q,
                                                          const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type*)
    : c(__q.c, __a),
      comp(__q.comp)
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

#ifndef _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
template <class _Alloc>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(const value_compare& __comp,
                                                          container_type&& __c,
                                                          const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type*)
    : c(_VSTD::move(__c), __a),
      comp(__comp)
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

template <class _Tp, class _Container, class _Compare>
template <class _Alloc>
inline
priority_queue<_Tp, _Container, _Compare>::priority_queue(priority_queue&& __q,
                                                          const _Alloc& __a,
                       typename enable_if<uses_allocator<container_type,
                                                         _Alloc>::value>::type*)
    : c(_VSTD::move(__q.c), __a),
      comp(_VSTD::move(__q.comp))
{
    _VSTD::make_heap(c.begin(), c.end(), comp);
}

#endif  // _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
inline
void
priority_queue<_Tp, _Container, _Compare>::push(const value_type& __v)
{
    c.push_back(__v);
    _VSTD::push_heap(c.begin(), c.end(), comp);
}

#ifndef _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
inline
void
priority_queue<_Tp, _Container, _Compare>::push(value_type&& __v)
{
    c.push_back(_VSTD::move(__v));
    _VSTD::push_heap(c.begin(), c.end(), comp);
}

template <class _Tp, class _Container, class _Compare>
template <class... _Args>
inline
void
priority_queue<_Tp, _Container, _Compare>::emplace(_Args&&... __args)
{
    c.emplace_back(_VSTD::forward<_Args>(__args)...);
    _VSTD::push_heap(c.begin(), c.end(), comp);
}

#endif  // _LIBCPP_CXX03_LANG

template <class _Tp, class _Container, class _Compare>
inline
void
priority_queue<_Tp, _Container, _Compare>::pop()
{
    _VSTD::pop_heap(c.begin(), c.end(), comp);
    c.pop_back();
}

template <class _Tp, class _Container, class _Compare>
inline
void
priority_queue<_Tp, _Container, _Compare>::swap(priority_queue& __q)
        _NOEXCEPT_(__is_nothrow_swappable<container_type>::value &&
                   __is_nothrow_swappable<value_compare>::value)
{
    using _VSTD::swap;
    swap(c, __q.c);
    swap(comp, __q.comp);
}

template <class _Tp, class _Container, class _Compare>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if<
    __is_swappable<_Container>::value
    && __is_swappable<_Compare>::value,
    void
>::type
swap(priority_queue<_Tp, _Container, _Compare>& __x,
     priority_queue<_Tp, _Container, _Compare>& __y)
    _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y)))
{
    __x.swap(__y);
}

template <class _Tp, class _Container, class _Compare, class _Alloc>
struct _LIBCPP_TEMPLATE_VIS uses_allocator<priority_queue<_Tp, _Container, _Compare>, _Alloc>
    : public uses_allocator<_Container, _Alloc>
{
};

_LIBCPP_END_NAMESPACE_STD

#endif  // _LIBCPP_QUEUE