/* deriv.h  compute formulas for numerical derivatives          */
/*          returns  npoints  values in  a  or  c               */
/*          0 <= polong < npoints                                */
/*          define 'digits' before use                          */
void deriv(long order, long npoints, long point, long *a, long *bb);
/* c[point][] = (1.0/((double)bb*h^order))*a[]                  */
void rderiv(long order, long npoints, long point, double h, double c[]);
/* c includes bb and h^order                                    */
/* derivative of f(x)    = c[0]*f(x+(0-point)*h) +              */
/*                         c[1]*f(x+(1-point)*h) +              */
/*                         c[2]*f(x+(2-point)*h) + ... +        */
/*                 c[npoints-1]*f(x+(npoints-1-point)*h         */