<queue>

Include the STL standard header <queue> to define the template classes priority_queue and queue, and several supporting templates.

namespace std {
template<class Ty, class Container>
    class queue;
template<class Ty, class Container, class Pr>
    class priority_queue;

        // TEMPLATE FUNCTIONS
template<class Ty, class Container>
    bool operator==(const queue<Ty, Container>& left,
        const queue<Ty, Container>&);
template<class Ty, class Container>
    bool operator!=(const queue<Ty, Container>& left,
        const queue<Ty, Container>&);
template<class Ty, class Container>
    bool operator<(const queue<Ty, Container>& left,
        const queue<Ty, Container>&);
template<class Ty, class Container>
    bool operator>(const queue<Ty, Container>& left,
        const queue<Ty, Container>&);
template<class Ty, class Container>
    bool operator<=(const queue<Ty, Container>& left,
        const queue<Ty, Container>&);
template<class Ty, class Container>
    bool operator>=(const queue<Ty, Container>& left,
        const queue<Ty, Container>&);
    };

operator!=

template<class Ty, class Container>
    bool operator!=(const queue <Ty, Container>& left,
        const queue <Ty, Container>& right);

The template function returns !(left == right).

operator==

template<class Ty, class Container>
    bool operator==(const queue <Ty, Container>& left,
        const queue <Ty, Container>& right);

The template function overloads operator== to compare two objects of template class queue. The function returns left.c == right.c.

operator<

template<class Ty, class Container>
    bool operator<(const queue <Ty, Container>& left,
        const queue <Ty, Container>& right);

The template function overloads operator< to compare two objects of template class queue. The function returns left.c < right.c.

operator<=

template<class Ty, class Container>
    bool operator<=(const queue <Ty, Container>& left,
        const queue <Ty, Container>& right);

The template function returns !(right < left).

operator>

template<class Ty, class Container>
    bool operator>(const queue <Ty, Container>& left,
        const queue <Ty, Container>& right);

The template function returns right < left.

operator>=

template<class Ty, class Container>
    bool operator>=(const queue <Ty, Container>& left,
        const queue <Ty, Container>& right);

The template function returns !(left < right).

priority_queue

template<class Ty,
    class Container = vector<Ty>,
    class Pr = less<typename Container::value_type> >
    class priority_queue {
public:
    typedef Container container_type;
    typedef typename Container::value_type value_type;
    typedef typename Container::size_type size_type;
    priority_queue();
    explicit priority_queue(const Pr& pred);
    priority_queue(const Pr& pred,
        const container_type& cont);
    priority_queue(const priority_queue& right);
    template<class InIt>
        priority_queue(InIt first, InIt last);
    template<class InIt>
        priority_queue(InIt first, InIt last,
            const Pr& pred);
    template<class InIt>
        priority_queue(InIt first, InIt last,
            const Pr& pred, const container_type& cont);
    bool empty() const;
    size_type size() const;
    const value_type& top() const;
    void push(const value_type& val);
    void pop();
protected:
    Container c;
    Pr comp;
    };

The template class describes an object that controls a varying-length sequence of elements. The object allocates and frees storage for the sequence it controls through a protected object named c, of class Container. The type Ty of elements in the controlled sequence must match value_type.

The sequence is ordered using a protected object named comp. After each insertion or removal of the top element (at position zero), for the iterators P0 and Pi designating elements at positions 0 and I, comp(*P0, *Pi) is false. (For the default template parameter less<typename Container::value_type> the top element of the sequence compares largest, or highest priority.)

An object of class Container must supply random-access iterators and several public members defined the same as for deque and vector (both of which are suitable candidates for class Container). The required members are:

    typedef Ty value_type;
    typedef T0 size_type;
    typedef T1 iterator;
    Container();
    template<class InIt>
        Container(InIt first, InIt last);
    template<class InIt>
        void insert(iterator where, InIt first, InIt last);
    iterator begin();
    iterator end();
    bool empty() const;
    size_type size() const;
    const value_type& front() const;
    void push_back(const value_type& val);
    void pop_back();

Here, T0 and T1 are unspecified types that meet the stated requirements.

priority_queue::container_type

typedef typename Container::container_type container_type;

The type is a synonym for the template parameter Container.

priority_queue::empty

bool empty() const;

The member function returns true for an empty controlled sequence.

priority_queue::pop

void pop();

The member function removes the first element of the controlled sequence, which must be non-empty, then reorders it.

priority_queue::priority_queue

priority_queue();
explicit priority_queue(const Pr& pred);
priority_queue(const Pr& pred,
    const container_type& cont);
priority_queue(const priority_queue& right);
template<class InIt>
    priority_queue(InIt first, InIt last);
template<class InIt>
    priority_queue(InIt first, InIt last,
        const Pr& pred);
template<class InIt>
    priority_queue(InIt first, InIt last,
        const Pr& pred, const container_type& cont);

All constructors with an argument cont initialize the stored object with c(cont). The remaining constructors initialize the stored object with c, to specify an empty initial controlled sequence. The last three constructors then call c.insert(c.end(), first, last).

All constructors also store a function object in comp. The function object comp is the argument pred, if present. For the copy constructor, it is right.comp. Otherwise, it is Pr().

A non-empty initial controlled sequence is then ordered by calling make_heap(c.begin(), c.end(), comp).

priority_queue::push

void push(const Ty& val);

The member function inserts an element with value val at the end of the controlled sequence, then reorders it.

priority_queue::size

size_type size() const;

The member function returns the length of the controlled sequence.

priority_queue::size_type

typedef typename Container::size_type size_type;

The type is a synonym for Container::size_type.

priority_queue::top

const value_type& top() const;

The member function returns a reference to the first (highest priority) element of the controlled sequence, which must be non-empty.

priority_queue::value_type

typedef typename Container::value_type value_type;

The type is a synonym for Container::value_type.

queue

template<class Ty,
    class Container = deque<Ty> >
    class queue {
public:
    typedef Container container_type;
    typedef typename Container::value_type value_type;
    typedef typename Container::size_type size_type;
    queue();
    explicit queue(const container_type& cont);
    bool empty() const;
    size_type size() const;
    value_type& back();
    const value_type& back() const;
    value_type& front();
    const value_type& front() const;
    void push(const value_type& val);
    void pop();
protected:
    Container c;
    };

The template class describes an object that controls a varying-length sequence of elements. The object allocates and frees storage for the sequence it controls through a protected object named c, of class Container. The type Ty of elements in the controlled sequence must match value_type.

An object of class Container must supply several public members defined the same as for deque and list (both of which are suitable candidates for class Container). The required members are:

    typedef Ty value_type;
    typedef T0 size_type;
    Container();
    bool empty() const;
    size_type size() const;
    value_type& front();
    const value_type& front() const;
    value_type& back();
    const value_type& back() const;
    void push_back(const value_type& val);
    void pop_front();
    bool operator==(const Container& cont) const;
    bool operator!=(const Container& cont) const;
    bool operator<(const Container& cont) const;
    bool operator>(const Container& cont) const;
    bool operator<=(const Container& cont) const;
    bool operator>=(const Container& cont) const;

Here, T0 is an unspecified type that meets the stated requirements.

queue::back

value_type& back();
const value_type& back() const;

The member function returns a reference to the last element of the controlled sequence, which must be non-empty.

queue::container_type

typedef Container container_type;

The type is a synonym for the template parameter Container.

queue::empty

bool empty() const;

The member function returns true for an empty controlled sequence.

queue::front

value_type& front();
const value_type& front() const;

The member function returns a reference to the first element of the controlled sequence, which must be non-empty.

queue::pop

void pop();

The member function removes the first element of the controlled sequence, which must be non-empty.

queue::push

void push(const Ty& val);

The member function inserts an element with value val at the end of the controlled sequence.

queue::queue

queue();
explicit queue(const container_type& cont);

The first constructor initializes the stored object with c(), to specify an empty initial controlled sequence. The second constructor initializes the stored object with c(cont), to specify an initial controlled sequence that is a copy of the sequence controlled by cont.

queue::size

size_type size() const;

The member function returns the length of the controlled sequence.

queue::size_type

typedef typename Container::size_type size_type;

The type is a synonym for Container::size_type.

queue::value_type

typedef typename Container::value_type value_type;

The type is a synonym for Container::value_type.

See also the Table of Contents and the Index.

Copyright © 1994-2002 by P.J. Plauger. Portions derived from work copyright © 1994 by Hewlett-Packard Company. All rights reserved.