queue

template<class T,
    class Cont = deque<T> >
    class queue {
public:
    typedef Cont::allocator_type allocator_type;
    typedef Cont::value_type value_type;
    typedef Cont::size_type size_type;
    explicit queue(const allocator_type& al = allocator_type()) const;
    bool empty() const;
    size_type size() const;
    allocator_type get_allocator() const;
    value_type& top();
    const value_type& top() const;
    void push(const value_type& x);
    void pop();
protected:
    Cont 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 Cont. The type T of elements in the controlled sequence must match value_type.

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

    typedef T value_type;
    typedef T0 size_type;
    Cont(const allocator_type& al);
    bool empty() const;
    size_type size() const;
    allocator_type get_allocator() const;
    value_type& front();
    const value_type& front() const;
    value_type& back();
    const value_type& back() const;
    void push_back(const value_type& x);
    void pop_front();

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