Thread: Data Structures

are these correct:

void ClearQueue(Queue *q)
{
q->count = 0;
q->front = 0;
q->rear = - 1;
}



void QueueFront(QueueEntry *x, Queue *q)
{
if (QueueEmpty(q))
Error('Queue is empty.");
else{
q->entry[q->front] = x;
}
}

void TraverseQueue(Queue(Queue *q, void (*Visit)(QueueEntry x));
{
int i;
for(i = 0; i < q->entry; i++)
*visit(q->entry[i];
}

Code:

void QueueFront (QueueEntry *x, Queue *q) 
{ 
    if (QueueEmpty (q)) 
        Error('Queue is empty."); 
    else
        q->entry[q->front] = x; 
}

If QueueEntry is an integer, and q->entry [i] is also an integer, then q->entry[q->front]=x should be q->entry[q->front]=*x;

Can you give the specifications of the functions? To me it seems that x is in output variable. So I would expect:

Code:

void QueueFront (QueueEntry *x, Queue *q) 
{ 
    if (QueueEmpty (q)) 
        Error('Queue is empty."); 
    else
        *x = q->entry[q->front]; 
}

It's just a matter of interpretation. But what I mean is: please make clear what your programs do, perhaps using pre- and postconditions, and show us what your datatypes are. Queue doesn't tell us very much. Though I guess it's a structure with an array and some variables in it.