result* calc_zeros(const function* &, int size, error* &);

int size = 3;
function* fkt = new function[size];
fkt[0] = f1;
fkt[1] = f2;
fkt[2] = f3;

result* calc_zeros(const function* & fkts, int size, error* & errors)
{
   if(size <= 1) return NULL;

   result* rs = new result[size];
   errors = new error[size];

   for(int i = 0; i < size; i++)
   {
   /* in result[i] wird die nullstelle der function fkts[i] gespeichert
       in errors[i] eventuell eine Fehlermeldung */   
   }
   return rs;
}

typedef double[] (*fp) (double a[], int n);

fp* fkt = new fp[3];

fkt[0] = f1;
fkt[1] = f2;
fkt[2] = f3;

//Aufruf:
ptrd = newton(fkt,3,&error);

double* newton(fp fkts[], int anzahl, int *error)
   {
      double * rs = new double[anzahl];
      error = new int[anzahl];

   for (int i=0; i<anzahl, i++)
         {...}

return rs;
}