Group 1: MakeEmptyQueue and Enqueue

Recall:

A 'Queue' is a 'First-In-First-Out' list where you insert new elements at the tail and remove existing elements from the head. The operations on a queue are MakeEmptyQueue, Enqueue, Serve, IsEmpty, IsFull.

Your Task:

Impelement the MakeEmptyQueue and the Enqueue procedures, as detailed below. Start with the MakeEmptyQueue procedure, which is basically only two lines. Then discuss the Enqueue routine, which is a little more complicated. When you are done, post both routines as two seperate postings on our bulletin board and we will discuss the routines together.

Details:

You have 15 minutes to come up with the two routines. Select one person as speaker of the group. When you have come up with your answer, the speaker should post the solutions on the bulletin board. Each of you might want to bring up Notepad for taking notes, if you like.

StdElement = Char;
NodePointer = ^Node;
Node = Record
             Data: StdElement;
             Next: NodePointer;
       end;
Queue = Record
              Head, Tail : NodePointer;
        end;

procedure MakeEmptyQueue(var Q: Queue);
{ PRE:  none }
{ POST: Creates a valid, empty queue                       }
procedure Enqueue(var Q: Queue; el: StdElement);
{ PRE:  The queue is not full }
{ POST: Q includes el as its most recently arrived element }