Oberon10.Scn.Fnt
Syntax10.Scn.Fnt
Syntax10b.Scn.Fnt
(* ETH Oberon, Copyright 2000 ETH Zuerich Institut fuer Computersysteme, ETH Zentrum, CH-8092 Zuerich.
Refer to the "General ETH Oberon System Source License" contract available at: http://www.oberon.ethz.ch/ *)
MODULE IFS; (** portable *)
(* Iterated Function System, page 92 *)
IMPORT RandomNumbers, In, Out, XYplane;
	a1, b1, c1, d1, e1, f1, p1: REAL; (* IFS parameters *)
	a2, b2, c2, d2, e2, f2, p2: REAL; (* IFS parameters *)
	a3, b3, c3, d3, e3, f3, p3: REAL; (* IFS parameters *)
	a4, b4, c4, d4, e4, f4, p4: REAL; (* IFS parameters *)
	X, Y: REAL;		(* the position of the pen *)
	x0: INTEGER;	(* Distance of origin fm left edge[pixels] *)
	y0: INTEGER;	(* Distance of origin from bottom edge[pixels] *)
	e: INTEGER;	(* Size of unit interval [pixels] *)
	initialized: BOOLEAN;	(* Are parameters initialized? *)
PROCEDURE Draw*;	(* command marked for export *)
	x, y: REAL; (* new position *)
	xi, eta: INTEGER; (* pixel coordinates of pen *)
	rn: REAL;
BEGIN
IF initialized THEN
	REPEAT
		rn := RandomNumbers.Uniform();
		IF rn < p1 THEN
			x := a1 * X + b1 * Y + e1;	y := c1 * X + d1 * Y + f1
		ELSIF rn < (p1 + p2) THEN
			x := a2 * X + b2 * Y + e2;	y := c2 * X + d2 * Y + f2
		ELSIF rn < (p1 + p2 + p3) THEN
			x := a3 * X + b3 * Y + e3;	y := c3 * X + d3 * Y + f3
		ELSE
			x := a4 * X + b4 * Y + e4;	y := c4 * X + d4 * Y + f4
		END;
		X := x; xi := x0 + SHORT(ENTIER(X*e));
		Y := y; eta := y0 + SHORT(ENTIER(Y*e));
		XYplane.Dot(xi, eta, XYplane.draw)
	UNTIL "s" = XYplane.Key()
END Draw;
PROCEDURE Init*;	(* command marked for export *)
BEGIN
	X := 0; Y := 0; (* Initial position of pen *)
	initialized := FALSE;
	In.Open;
	In.Int(x0); In.Int(y0); In.Int(e);
	In.Real(a1); In.Real(a2); In.Real(a3); In.Real(a4);
	In.Real(b1); In.Real(b2); In.Real(b3); In.Real(b4);
	In.Real(c1); In.Real(c2); In.Real(c3); In.Real(c4);
	In.Real(d1); In.Real(d2); In.Real(d3); In.Real(d4);
	In.Real(e1); In.Real(e2); In.Real(e3); In.Real(e4);
	In.Real(f1); In.Real(f2); In.Real(f3); In.Real(f4);
	In.Real(p1); In.Real(p2); In.Real(p3); In.Real(p4);
	IF In.Done THEN XYplane.Open; initialized := TRUE
	ELSE Out.String("Parameter error"); Out.Ln
END Init;
BEGIN initialized := FALSE
END IFS. (* Copyright M. Reiser, 1992 *)
IFS.Init 200 50 40
0.0 0.85 0.2 -0.15
0.0 0.04 -0.26 0.28
0.0 -0.04 0.23 0.26
0.16 0.85 0.22 0.24
0.0 0.0 0.0 0.0 
0.0 1.6 1.6 0.44
0.01 0.85 0.07 0.07 ~
IFS.Draw