queue.h

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//顺序循环队列的模板类接口定义以及基本运算的实现代码
#include<iostream.h>
enum Error_code{ success, overflow, underflow, can_land, can_depart, fail };
const int maxqueue = 10; // small value for testing
template <class Queue_entry> class Queue
{ public:
    Queue( );
    bool empty( ) const { return count==0;  }
    Error_code serve( );
    Error_code append(const Queue_entry &item);
    Error_code retrieve(Queue_entry &item) const;
  protected:
    int count;
    int front, rear;
    Queue_entry entry[maxqueue];
    friend class Runway; 
};

template <class Queue_entry>class Extended_queue:public Queue<Queue_entry>
{ public:
  bool full( ) const {  return  count==int_maxqueue; }
  int size( ) const {  return count;  }
  void clear( ) { count=0;  rear=maxqueue-1;  front=0; }
  Error_code serve_and_retrieve(Queue_entry &item) { retrieve(); }
  friend class Runway; 
};

template <class Queue_entry>Queue<Queue_entry>::Queue( )
// Post: TheQueue is initialized to be empty. 
{ count=0;
  rear=maxqueue-1;
  front=0;
}

template <class Queue_entry>Error_code Queue<Queue_entry>::append(const Queue_entry &item)
// Post: item is added to the rear of the Queue . If the Queue is full return an
// Error_code of over flow and leave the Queue unchanged.
{ if(count>=maxqueue) return overflow;
  count++;
  rear=((rear+1)==maxqueue)? 0: (rear+1);
  entry[rear]=item;
  return success;
}
template <class Queue_entry>Error_code Queue<Queue_entry>::serve( )
// Post: The front of the Queue is removed. If the Queue is empty return an Error_code of underflow.
{ if(count<=0) return underflow;
  count--;
  front=((front+1)==maxqueue)? 0 : (front+1);
  return success;
}
template <class Queue_entry>Error_code Queue<Queue_entry>::retrieve(Queue_entry &item) const
// Post: The front of theQueue retrieved to the output parameteritem . If theQueue is empty return anError_code ofunderflow.
{
  if(count<=0) return underflow;
  item = entry[front];
  return success;
}