-- rderiv.adb  compute coefficients for numerical derivatives a(0)...
--             order is order of derivative, 1 = first derivative, 2 = second
--             npoints is number of points where value of function is known
--             f(x1), f(x2), f(x3) ... f(x npoints)
--             xi+1 = xi + h
--             term is the point where derivative is computed
--             f'(xt) =  aa(1) * f(x1) + aa(2) * f(x2)
--                      + ... + aa(points) * f(x points)
--             see nuderiv for unequally spaced points

with Ada.text_io;
use  Ada.text_io;
with Real_Arrays;
use Real_Arrays;
with Nuderiv;

procedure rderiv(order   : integer;
                 npoints : integer;
                 point   : integer;
                 hx      : Real;
                 C       : out Real_Vector) is

  xg : Real_Vector(1..npoints);
  a : Real_Vector(1..npoints);
  hpower : Real;
begin
  for i in 1..npoints loop
    xg(i) := Real(i-1);
  end loop;
  Nuderiv(order, npoints, point, xg, a);
  hpower := hx;
  for i in 2..Order loop
    hpower := hpower * hx;
  end loop;
  for i in 1..npoints loop
    c(i) := a(i)/hpower;
  end loop;
end rderiv;