Exercises 3.3 E7

E7    Rewrite the methods for queue processing from the text ,using a flag to indicate a full queue  instead of keeping a count of the entries in the queue

 

The class definition for this Queue implementation is as follows.
const  int maxqueue=10;    //small value for testing
class Queue {
Public:
   Queue();
   bool empty()const;
   Error_code serve();
   Error_code append(const Queue_entry &item);
   Error_code retrieve(Queue_entry &item) const;
Protected;
   int front,rear;
   Queue_entry entry[maxqueue];
   Bool is_empty;
}
The method implementations follow
Queue::Queue()
{
  Rear=-1;
  Front=0;
  Is_empty=true;
}
bool Queue::empty()const
{
  return is_empty;
}
Error_code Queue::append(const Queue_entry&item)
{
   if {!empty()&&(rear+1)%maxqueue==front}return overflow;
   is_empty=false;
   rear =((rear+1)==maxqueue)?0:(rear+);
   entry[rear]=item;
   return success;
}
Error_code Queue::serve()
{
if(empty())return undeflow;
if(rear==front)is_empty=true;
front=((front+1)==maxqueue)?0:(front+1);
return success;
}
Error_code Queue::retrieve(Queue_entry&item)const
{
  if(empty())return undflow;
   Item=entry[front];
return success
}