#ifndef _APSTACK_H  #define _APSTACK_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  //  - abort -->> exit  //  // APCS stack class  // *******************************************************************    #include "apvector.h"                  // used for stack implementation    template   class apstack  {    public:          // constructors/destructor        apstack( );                            // construct empty stack      apstack( const apstack & s );          // copy constructor      ~apstack( );                           // destructor      // assignment        const apstack & operator = ( const apstack & rhs );      // accessors        const itemType & top( )      const;   // return top element (NO pop)      bool             isEmpty( )  const;   // return true if empty, else false      int              length( )   const;   // return number of elements in stack      // modifiers        void push( const itemType & item );   // push item onto top of stack      void pop( );                          // pop top element      void pop( itemType & item );          // combines pop and top      void makeEmpty( );                    // make stack empty (no elements)      private:        int myTop;                            // index of top element      apvector myElements;        // storage for stack  };      // **********************************************************************    //    // Specifications for stack functions    //    // Any violation of a function's precondition will result in an error message    // followed by a call to exit.    //    //    // constructors/destructor    //    //  apstack( )    //    postcondition: the stack is empty    //    //  apstack( const apstack & s )    //    postcondition: stack is a copy of s    //    //  ~apstack( )    //    postcondition: stack is destroyed    //    // assignment    //    //  const apstack & operator = ( const apstack & rhs )    //    postcondition: normal assignment via copying has been performed    //    // accessors    //    //  const itemType & top( ) const    //    precondition: stack is [e1, e2, ... en] with n >= 1    //    postcondition: returns en    //    //  bool isEmpty( ) const    //     postcondition: returns true if stack is empty, false otherwise    //    //  int length( ) const    //     postcondition: returns # of elements currently in stack    //    // modifiers    //    //  void push( const itemType & item )    //     precondition: stack is [e1, e2...en] with  n >= 0    //     postcondition: stack is [e1, e2, ... en, item]    //    //  void pop( )    //     precondition: stack is [e1, e2, ... en] with n >= 1    //     postcondition: stack is [e1, e2, ... e(n-1)]    //    //    //  void pop(itemType & item )    //     precondition: stack is [e1,e2,...en] with n >= 1    //     postcondition: stack is [e1,e2,...e(n-1)] and item == en    //    //  void makeEmpty( )    //     postcondition:  stack is empty    //    //  Examples of variable definition     //    //    apstack istack;                    // creates empty stack of integers    //    apstack dstack;                 // creates empty stack of doubles    //    #include "apstack.cpp"    #endif