/*Source*/
import Lsystem;

size(8cm,0);
Lsystem Koch=Lsystem("+F--F--F",
                     new string[][]{{"F","F+F--F+F"}},
                     La=60, Lai=0);
Koch.iterate(4);
filldraw(Koch.paths()[0]&cycle, paleyellow, 1bp+black);
shipout(bbox(2mm, Fill(lightyellow)));

    
/* Source */
import Lsystem;
size(10cm,0);

Lsystem SierpinskiCarpet=
  Lsystem("F+F+F+F",
          new string[][]{{"F","FF+F+F+F+FF"}},
          La=90, Lai=0);
SierpinskiCarpet.iterate(4);
draw(SierpinskiCarpet.paths(), bp+0.2*green);

shipout(bbox(Fill(paleyellow)));

    
import Lsystem;
size(10cm,0);

Lsystem SierpinskiCurve=
  Lsystem("YF",
          new string[][]{{"X","YF+XF+Y"},{"Y","XF-YF-X"}},
          La=60, Lai=0);
SierpinskiCurve.iterate(7);
draw(SierpinskiCurve.paths(), bp+0.2*green);

shipout(bbox(Fill(paleyellow)));

    
import Lsystem;
size(10cm);

string[][] rules={{"F","FF"}, {"X","--FXF++FXF++FXF--"}};
Lsystem Sierpinski=Lsystem("FXF--FF--FF", rules, La=60, Lai=0);
Sierpinski.iterate(5);
draw(Sierpinski.paths(), bp+0.2*green);

shipout(bbox(Fill(paleyellow)));