Exercise 3.3E7

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

}3.3