Re: Decent datastructure for queue operations

Oops.. I was mistaken with the `last' function which of course does not
jump in no time to the end of a list.

Glenn: thanks for the chapter, it's helpful.

To Kaz: the idea of using a hash table along side a list is not a bad
idea, indeed. The only problem I encountered was the data structures
became too big when many queues were in use.

It doesn't have to be a priority queue, but the items should never be
enqueued once they are there.

.