PROGRAM d3r3 (input,output);
(* driver for routine SPLINE *)
CONST
   n=20;
   pi=3.1415926;
TYPE
   glnarray = ARRAY [1..n] OF real;
VAR
   i : integer;
   yp1,ypn : real;
   x,y,y2 : glnarray;

(*$I MODFILE.PAS *)
(*$I SPLINE.PAS *)

BEGIN
   writeln ('second-derivatives for sin(x) from 0 to pi');
(* generate array for interpolation *)
   FOR i := 1 to 20 DO BEGIN
      x[i] := i*pi/n;
      y[i] := sin(x[i])
   END;
(* calculate 2nd derivative with spline *)
   yp1 := cos(x[1]);
   ypn := cos(x[n]);
   spline(x,y,n,yp1,ypn,y2);
(* test result *)
   writeln ('spline':23,'actual':16);
   writeln ('number':11,'2nd deriv':14,'2nd deriv':16);
   FOR i := 1 to n DO BEGIN
      writeln (i:8,y2[i]:16:6,-sin(x[i]):16:6)
   END
END.