Call:   result = evalPoly(x0,a)
    

float evalPoly(float x0, PolyPointer ptr)
{/*evaluate the polynomial at point x */
  PolyPointer temp;
  float result = 0;
  for (temp = ptr; temp; temp= temp->link) 
    result = result + temp->coef * pow(x0,temp->expon);
  return result;
}