Here are my suggestions for this exercise
Enjoy !!!


I give the class, then the methods i think it needs below.


ComptonDatum
------------

// This method is to initialise it from the values in the file
// This is just like ThreeVector
initialise( float angle, float energy, float error )

// This method is to calculate the chisq contribution from this datum
float chiSquared( float mass )


Histogram
----------

// Do this later




DataReader
--------------

// Only needs one method, 
// Its job is to go to the specified file, read it and for each line
// create a new ComptonDatum. These should be pushed into a vector
// which is then returned to the caller of the method

vector<ComptonDatum> getData( string filename ) 


Minimiser
---------

// To set the initial guess at the mass, and the chisq change for convergence
initialise( float initialParameter, float convergence ) 

// gives the client the current guess at the mass 
float getCurrentParameter( )

// You use this to give the minimiser the chisq corresponding to the mass
// it gave you
void setChiSquared( float chisq )


//--------------------------------------------------------
// Here is some (incomplete) code to outline how it might all work together.

int main()
{

  // Read file and create datum objects 

  vector<ComptonDatum> measurements ;

  DataReader myReader ;

  measurements = myReader.getFromFile( "filename" ) ;


  // Make a minimiser and intialise it
  Minimiser massFitter ;
    
  float mass = 500 ;
  massFitter.initialise( mass )  

  while( massFitter.isMinimising() )
  {

    mass = massFitter.getCurrentParameter( ) ;

    float chisq = 0 ;

    for( ............. )
    {
      chisq += measurements[ind].chiSquared( mass ) ;
    }

    massFitter.setChiSquared( chisq ) ;

  }  

  // print out final mass

  mass = massFitter.getCurrentParameter( ) ;

  cout << ......