Dispensers all have the property that they can "dispense" their
  contained items in some order.

    dispenser.sa -has dispenser.sa $DISPENSER -- Dispensers abstraction
					      -- for containers such as stacks
    queue.sa -has queue.sa $QUEUE 
    a_queue.sa -has a_queue.sa A_QUEUE QUEUE 

    stack.sa -has stack.sa $STACK 
    nr_stack.sa -has nr_stack.sa $NR_STACK
    a_stack.sa -has a_stack.sa A_STACK STACK 
    nr_a_stack.sa -has nr_a_stack.sa NR_A_STACK STACK 

    pq.sa -has pq.sa  $PQ -- Priority queue
    a_pq.sa -has a_pq.sa  A_PQ PQMIN PQWT PQMINWT

    queue_test.sa -has queue_test.sa TEST_QUEUE 
    stack_test.sa -has stack_test.sa TEST_STACK 
    pq_test.sa -has pq_test.sa  TEST_PQ