Расчет введенной формулы

Code:

uses Recognition;

procedure TForm1.Button1Click(Sender: TObject);

const

left = -10;

right = 10;

YScale = 50;

k = 10;

var

i: integer;

Num: extended;

s: String;

XScale: single;

col: TColor;

begin

s := Edit1.Text;

preparation(s, ['x']);

XScale := PaintBox1.Width / (right - left);

randomize;

col := RGB(random(100), random(100), random(100));

for i := round(left * XScale * k) to round(right * XScale * k) do

   if recogn(ChangeVar(s, 'x', i / XScale / k), Num) then

     PaintBox1.Canvas.Pixels[round(i / k - left * XScale),

       round(PaintBox1.Height / 2 - Num * YScale)] := col;

end;