#ifndef _APQUEUE_H  #define _APQUEUE_H    // uncomment line below if bool not built-in type  // #include "bool.h"    // *******************************************************************  // Last Revised: 8-14-98  //  //  - commented out the #include "bool.h", dhj  //  - updated comments for constructor/descructor, dhj  //  // APCS queue class  // *******************************************************************    #include "apvector.h"                       // used to implement queue    template   class apqueue  {    public:      // constructors/destructor        apqueue( );                                 // construct empty queue      apqueue( const apqueue & q );               // copy constructor      ~apqueue( );                                // destructor      // assignment        const apqueue & operator = ( const apqueue & rhs );      // accessors        const itemType & front( )   const;    // return front (no dequeue)      bool             isEmpty( ) const;    // return true if empty else false      int              length( )  const;    // return number of elements in queue      // modifiers        void enqueue( const itemType & item );    // insert item (at rear)      void dequeue( );                          // remove first element      void dequeue( itemType & item );          // combine front and dequeue      void makeEmpty( );                        // make queue empty       private:           int mySize;                    // # of elts currently in queue      int myFront;                   // index of first element      int myBack;                    // index of last element      apvector myElements; // internal storage for elements            // private helper functions      void DoubleQueue();              // double storage for myElements      void Increment(int & val) const; // add one with wraparound   };    // *******************************************************************  // Specifications for queue functions  //  // Any violation of a function's precondition will result in an error   // message followed by a call to exit.  //  // constructors/destructor  //  //  apqueue( )  //     postcondition: the queue is empty  //  //  apqueue( const apqueue & q )  //     postcondition: queue is a copy of q  //  //  ~apqueue( )  //     postcondition: queue is destroyed  //  // assignment  //  //  const apqueue & operator = ( const apqueue & rhs )  //     postcondition: normal assignment via copying has been performed  //  // accessors  //  //  const itemType & front( ) const  //     precondition: queue is [e1, e2, ..., en] with n >= 1  //     postcondition: returns e1  //  //  bool isEmpty( ) const  //     postcondition: returns true if queue is empty, false otherwise  //  //  int length( ) const  //     precondition: queue is [e1, e2, ..., en] with n >= 0  //     postcondition:  returns n  //  // modifiers:  //  //  void enqueue( const itemType & item )  //     precondition: queue is [e1, e2, ..., en] with n >= 0  //     postcondition: queue is [e1, e2, ..., en, item]  //  //  void dequeue( )  //     precondition: queue is [e1, e2, ..., en] with n >= 1  //     postcondition: queue is [e2, ..., en]  //  //  void dequeue( itemType & item )  //     precondition: queue is [e1, e2, ..., en] with n >= 1  //     postcondition:  queue is [e2, ..., en] and item == e1  //  //  void makeEmpty( )  //     postcondition: queue is empty  //  // Examples for use:  //  //    apqueue iqueue;             // creates empty queue of integers  //    apqueue dqueue           // creates empty queue of doubles    #include "apqueue.cpp"      #endif