macintosh_cookbook/examples/julia.pas

program ExampleJulia;

 const
  scale = 0.01;
  R = 10;

 type
  complex = record
    r: Real;
    i: real
   end;

 var
  i, j, k, n, row, col, Nit: Integer;
  x, y: Real;
  z, znew, c: complex;
  done, gone: Boolean;
  drawingRect: Rect;

 procedure prod (a, b: complex; var c: complex);
 begin
  c.r := a.r * b.r - a.i * b.i;
  c.i := a.r * b.i + a.i * b.r;
 end;

 procedure add (a, b: complex; var c: complex);
 begin
  c.r := a.r + b.r;
  c.i := a.i + b.i;
 end;

 procedure plot (c, r: integer);
 begin
  Moveto(c, r);
  Lineto(c, r);
 end;

begin

 ShowText;
 Writeln('Value of Nit,Cr,Ci?');
 ReadLn(Nit, c.r, c.i);

 Showdrawing;
 SetRect(drawingRect, 200, 40, 600, 400);
 SetDrawingRect(drawingRect);

 ForeColor(blackColor);
 n := 0;
 for col := 1 to 400 do
  for row := 1 to 400 do
   begin
    z.r := (col - 200) * scale;
    z.i := (row - 200) * scale;
    repeat
     prod(z, z, znew);
     add(znew, c, z);
     gone := (z.r * z.r + z.i * z.i > R);
     n := n + 1;
     done := (n > Nit);
    until done or gone or button;
    if done then
     plot(col, row);
    n := 0;
   end;

end.

{ note: Interesting fractals }
{ 10 0   1 }
{ 50 0.3 -0.5 }