USES SPLIN;
{ Porovnava 1. derivaci funkce cos x s hodnotou ziskanou pomoci splinu
  zadavaji se derivace na okraji jako okraj. podm.
  vysledek se pise do souboru SPL1.DAT}
const
  pi = 3.141592;
{  nbod = 51;
  ndel = 501;}
var
   X,Y, Y2, Y1kon, y1spl : RealArrayNP;
   xmax,xmin,xr,yp1,ypn,dx,y21,xh,ygs,yfs,dx1: Real;
   i,nbod : integer;
   f1 : text;
BEGIN
   ASSIGN(f1,'spl1.dat');
   REWRITE(f1);
   Writeln('ZADEJ xmin,xmax,nbod');
   Readln(xmin,xmax,nbod);
   dx := (xmax - xmin)/(nbod - 1);
   FOR i := 1 to nbod DO BEGIN
      x[i] := xmin + (i-1)*dx;
      y[i] := cos(x[i]);
      y1kon[i] := -sin(x[i])
   END;
   Writeln (' Zadej derivaci y pro xmin, xmax');
   Readln(yp1,ypn);
   Spline(X,Y,nbod,yp1,ypn,Y2);
   FOR i:= 1 TO nbod-1 DO BEGIN
       xr := (x[i+1]-x[i]);
       y1spl[i]:= (y[i+1]-y[i])/xr - xr*(y2[i]/3 + y2[i+1]/6)
       END;
   y1spl[nbod] := (y[nbod]-y[nbod-1])/xr + xr*(y2[nbod-1]/6+y2[nbod]/3);
   WRITELN('   x        y        d1teor       d1spl');
   FOR i := 1 TO nbod DO BEGIN
       writeln(x[i],y[i],y1kon[i],y1spl[i]);
       writeln(f1,x[i],y[i],y1kon[i],y1spl[i])
       END;
   CLOSE(f1)
END.