class Stac {
  // default is private access
  static int MAXVAL;    // maximum size of stack
  int _sp;              // next free stack position
  double **_val;        // array stack
  
 public:
  Stac();
  Stac(int);
  ~Stac(void);
  
  void push(double *a);
  double *pop(void);
  void maxval(int max);
  void maxval(void);
};