23 Containers library [containers]

23.6 Container adaptors [container.adaptors]

23.6.4 Class template priority_queue [priority.queue]

Any sequence container with random access iterator and supporting operations front(), push_back() and pop_back() can be used to instantiate priority_queue. In particular, vector ([vector]) and deque ([deque]) can be used. Instantiating priority_queue also involves supplying a function or function object for making priority comparisons; the library assumes that the function or function object defines a strict weak ordering ([alg.sorting]).

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

  public:
    priority_queue(const Compare& x, const Container&);
    explicit priority_queue(const Compare& x = Compare(), Container&& = Container());
    template <class InputIterator>
      priority_queue(InputIterator first, InputIterator last,
             const Compare& x, const Container&);
    template <class InputIterator>
      priority_queue(InputIterator first, InputIterator last,
             const Compare& x = Compare(), Container&& = Container());
    template <class Alloc> explicit priority_queue(const Alloc&);
    template <class Alloc> priority_queue(const Compare&, const Alloc&);
    template <class Alloc> priority_queue(const Compare&,
      const Container&, const Alloc&);
    template <class Alloc> priority_queue(const Compare&,
      Container&&, const Alloc&);
    template <class Alloc> priority_queue(const priority_queue&, const Alloc&);
    template <class Alloc> priority_queue(priority_queue&&, const Alloc&);

    bool      empty() const       { return c.empty(); }
    size_type size()  const       { return c.size(); }
    const_reference   top() const { return c.front(); }
    void push(const value_type& x);
    void push(value_type&& x);
    template <class... Args> void emplace(Args&&... args);
    void pop();
    void swap(priority_queue& q) noexcept(
        noexcept(swap(c, q.c)) && noexcept(swap(comp, q.comp)))
      { using std::swap; swap(c, q.c); swap(comp, q.comp); }
  };
  // no equality is provided
  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)));

  template <class T, class Container, class Compare, class Alloc>
    struct uses_allocator<priority_queue<T, Container, Compare>, Alloc>
      : uses_allocator<Container, Alloc>::type { };
}

23.6.4.1 priority_queue constructors [priqueue.cons]

priority_queue(const Compare& x, const Container& y); explicit priority_queue(const Compare& x = Compare(), Container&& y = Container());

Requires: x shall define a strict weak ordering ([alg.sorting]).

Effects: Initializes comp with x and c with y (copy constructing or move constructing as appropriate); calls make_heap(c.begin(), c.end(), comp).

template <class InputIterator> priority_queue(InputIterator first, InputIterator last, const Compare& x, const Container& y); template <class InputIterator> priority_queue(InputIterator first, InputIterator last, const Compare& x = Compare(), Container&& y = Container());

Requires: x shall define a strict weak ordering ([alg.sorting]).

Effects: Initializes comp with x and c with y (copy constructing or move constructing as appropriate); calls c.insert(c.end(), first, last); and finally calls make_heap(c.begin(), c.end(), comp).

23.6.4.2 priority_queue constructors with allocators [priqueue.cons.alloc]

If uses_allocator<container_type, Alloc>::value is false the constructors in this subclause shall not participate in overload resolution.

template <class Alloc> explicit priority_queue(const Alloc& a);

Effects: Initializes c with a and value-initializes comp.

template <class Alloc> priority_queue(const Compare& compare, const Alloc& a);

Effects: Initializes c with a and initializes comp with compare.

template <class Alloc> priority_queue(const Compare& compare, const Container& cont, const Alloc& a);

Effects: Initializes c with cont as the first argument and a as the second argument, and initializes comp with compare.

template <class Alloc> priority_queue(const Compare& compare, Container&& cont, const Alloc& a);

Effects: Initializes c with std::move(cont) as the first argument and a as the second argument, and initializes comp with compare.

template <class Alloc> priority_queue(const priority_queue& q, const Alloc& a);

Effects: Initializes c with q.c as the first argument and a as the second argument, and initializes comp with q.comp.

template <class Alloc> priority_queue(priority_queue&& q, const Alloc& a);

Effects: Initializes c with std::move(q.c) as the first argument and a as the second argument, and initializes comp with std::move(q.comp).

23.6.4.3 priority_queue members [priqueue.members]

void push(const value_type& x);

Effects:

c.push_back(x);
push_heap(c.begin(), c.end(), comp);

void push(value_type&& x);

Effects:

c.push_back(std::move(x));
push_heap(c.begin(), c.end(), comp);

template <class... Args> void emplace(Args&&... args)

Effects:

c.emplace_back(std::forward<Args>(args)...);
push_heap(c.begin(), c.end(), comp);

void pop();

Effects:

pop_heap(c.begin(), c.end(), comp);
c.pop_back();

23.6.4.4 priority_queue specialized algorithms [priqueue.special]

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

Effects: x.swap(y).