> restart:


> ifs:=proc(imax)
> # original program 'Chaos-Spiel fuer ein Farnblatt' written by 
> # Heinz-Otto Peitgen, Hartmut Juergens and Dietmar Saupe  
> # in BASIC 
>    local e1, e2, e3, e4, f1, f2, f3, f4, x, y, xn, yn, z, i, pts;
>    x:=e1;
>    y:=0;
>    pts:=NULL;
>    e1:=0.5; e2:=0.57; e3:=0.408; e4:=0.1075;
>    f1:=0; f2:=-0.036; f3:=0.0893; f4:=0.27;
>    x:=e1;
>    y:=0;
>    for i from 1 to imax do
>       z:=rand()/1e12;
>       if z<=0.02 then 
>          xn:=e1;
>          yn:=0.27*y+f1;
>          goto(100);
>       fi;
>       if z<=0.17 then
>          xn:=-0.139*x+0.263*y+e2;
>          yn:=0.246*x+0.224*y+f2;
>          goto(100);
>       fi;
>       if z<=0.3 then 
>          xn:=0.17*x-0.215*y+e3;
>          yn:=0.222*x+0.176*y+f3;
>          goto(100);
>       fi;
>       xn:=0.781*x+0.034*y+e4;
>       yn:=-0.032*x+0.739*y+f4;
>       100:
>       pts:=pts, [xn, yn];
>       x:=xn;
>       y:=yn;
>    od;
>    [pts];
> end:


> plot(ifs(10000), axes=NONE, style=point, symbol=POINT, scaling=constrained);


>