//  Acceleration class 
//  -----------

#ifndef ACCELERATION
#define ACCELERATION const Acceleration
class Mass;                         //  Interacting
class Force;                        //    classes
class Velocity;                       
class Time;

//  This class supports 3-dimensional force quantities

#include <math.h>                  /*  (for sqrt)                        */

 class Acceleration {

   double value[3];               

 public:
   
//  Constructors and accessors
//  --------------------------

  Acceleration(DOUBLE x=0, DOUBLE y=0, DOUBLE z=0)  
    {value[0]=x; value[1]=y; value[2]=z;}       

//  The compiler will provide an acceptable copy constructor,
//  destructor, and assignment operator.

  double magnitude() const 
    {return sqrt(value[0]*value[0] + value[1]*value[1] + value[2]*value[2]);}

  double x()       const {return value[0];}
  double y()       const {return value[1];}
  double z()       const {return value[2];}


//  

//  Operations on Acceleration quantities
//  -------------------------------------

    Acceleration operator-() const
    {return Acceleration(-value[0], -value[1], -value[2]);}

    bool operator==(ACCELERATION rs) const
    {return value[0] == rs.value[0] 
         && value[1] == rs.value[1]
         && value[2] == rs.value[2];
    }
    bool operator <(ACCELERATION rs) const
    {return magnitude() < rs.magnitude();}
   
//  Operations on mixed quantities

    Force        operator*(const Mass  rs) const; 
    Velocity     operator*(const Time  rs) const;
    

};                          //  *****  End of class definition


 inline ostream& operator<<(ostream& ls, ACCELERATION rs) // Output stream insertion
 {return ls << '(' << rs.x() << ',' 
                   << rs.y() << ',' 
                   << rs.z() << ") cm/secē";}
     
#undef Class
#endif