/* University College London Dept of Physics Course in C++ 3C59 
| all rights reserved 1999 
|
| Utility: DECLARATION of the ThreeVector class
|
| This is the second attempt which now includes some methods, 
| (but is still incomplete as there are no constructors)
|
| Author: P.Clarke 
*/

#ifndef  _threevec_secondgo_h
#define  _threevec_secondgo_h 1

#include <cmath>
#include <iostream>

class ThreeVector 
{

  private: 
    float px ; 
    float py ;
    float pz ;

  public:

  // To initialise the vector with 3 cartesian momentum components
  // Note:  this method should NOT be used after we have covered constructors
  void initialise( float qx, float qy, float qz ) 
  {
    px = qx ;
    py = qy ;
    pz = qz ;
  }

  // To return the square of the magnitude 
  float magnitudesq( ) 
  {
     return ( px*px + py*py + pz*pz ) ;
  }

  // To return the magnitude 
  float magnitude( ) 
  {
    return sqrt( magnitudesq( ) );
  }

  // To return the phi angle in the x-y plane 
  float phi( ) 
  {
    return acos( px / sqrt(px*px + py*py) ) ;
  }


  // To perform the dot product of two vectors 
  float dotProduct( ThreeVector t2 ) 
  {
    return ( px*t2.px + py*t2.py + pz*t2.pz ) ;
  }



  // To calculate the angle between two vectors in radians
  float angle( ThreeVector t2 ) 
  {
    float angle ;
    angle = dotProduct( t2 ) / magnitude( ) / t2.magnitude(  ) ;
    angle = acos(angle) ;
    return angle ;
  }


  // To dump out the contents to cout
  void dump( )
  {
    std::cout << " The vector contents are " 
              << " px= " << px  
              << " py= " << py  
              << " pz= " << pz
              << std::endl ;
  }
 
};

#endif