User's Guide to the GNU C++ Class Library

Chapter 30: Queues

Queues are declared as an ``abstract'' class. They are currently implemented in any of three ways.

VQueue

implement fixed sized Queues via arrays.

XPQueue

implement dynamically-sized Queues via XPlexes.

SLQueue

implement dynamically-size Queues via linked lists.

All possess the same capabilities; they differ only in constructors. VQueue constructors require a fixed maximum capacity argument. XPQueue constructors optionally take a chunk size argument. SLQueue constructors take no argument.

Assume the declaration of a base element x.

Queue q; or Queue q(int capacity);

declares a queue.

q.empty()

returns true if queue q is empty.

q.full()

returns true if queue q is full. XPQueues and SLQueues are never full.

q.length()

returns the current number of elements in the queue.

q.enq(x)

enqueues x on queue q.

x = q.deq()

dequeues and returns the front of queue

q.front()

returns a reference to the front of queue.

q.del_front()

dequeues, but does not return the front of queue

q.clear()

removes all elements from the queue.