#include <iostream.h>
#include <math.h>
#include <cfortran/cfortran.h>

extern "C" {
  void  fcn(int npar, double grad[2], double * fcnval,
          double xval[2], int iflag, void * futil);
           }

FCALLSCSUB6(fcn,FCN,fcn,INT,DOUBLEV,PDOUBLE,DOUBLEV,INT,ROUTINE)

extern "C" void fcn(int npar, double grad[2], double * fcnval, 
double par[2], int iflag, void * futil)
{

  extern int num_points;
  extern double x[], y[], dy[];

  double alpha = par[0];
  double beta  = par[1];
  double chi2 = 0.;
  for(int i =0; i<num_points; i++)
  {
    double f = alpha * pow(x[i],beta);
    chi2 = chi2 + pow(y[i] - f,2) / pow(dy[i],2);
  }
  *fcnval = chi2;

}