/* University College London dept of physics course in C++ 3C59 
| all rights reserved 1999 
|
| Example: Dot Product
|
| "First First use of ThreeVector class 
|   Used to make 3-vector dot product simpler "
|
| Author: P.Clarke 
*/

#include <iostream>
#include <cmath>

#include "../util/ThreeVector_firstgo.h"



///.......................................
// Here is the new  dot product function 

float dotProduct( ThreeVector v, ThreeVector w )
{
  return (v.px*w.px) + (v.py*w.py) + (v.pz*w.pz) ;
}




//......................................
// Here is the new magnitude function   

float magnitude( ThreeVector v  )
{
  return sqrt( (v.px*v.px) + (v.py*v.py) + (v.pz*v.pz) ) ;
}



//..............
// Main program 

int main() 
{

  // Declare some  3-vectors 
  ThreeVector vec1 ;
  ThreeVector vec2 ;


  // Set them to something 
  vec1.px = 1. ;
  vec1.py = 1.5 ;
  vec1.pz = 1.6 ;

  vec2.px = -0.3 ;
  vec2.py = 1.2 ;
  vec2.pz = 1. ;

  // .... wouldnt it be a good idea to write an initialise(..)
  // .... funtion to do the above......

  // Take the dot product 

  float prod ;

  prod =  dotProduct( vec1, vec2 )  ;



  // Calculate the magnitude of each vector 

  float mag1, mag2 ;

  mag1 = magnitude( vec1 ) ;
  mag2 = magnitude( vec2 ) ;



  // Calculate the cosine of the angle between the vectors,
  // and then find the angle itself 

  float cosTheta, theta ;

  cosTheta = prod / mag1 / mag2 ;

  theta = acos( cosTheta ) ;



  // Finally print it out 


  std::cout << "TTTTTTTTTTTTTTTT 3C59 example TTTTTTTTTTTTTTTT" << std::endl ;

  std::cout << " dprod3: This is the (slightly more) improved version " << std::endl ;

  std::cout << " The angle is " 
            << theta 
            << " radians "
            << std::endl ;

  std::cout << "LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL" << std::endl ;




  return 1 ;

}