Task
Produce a graphical or ASCII-art representation of a  Sierpinski arrowhead curve  of at least order  3.




USING: accessors L-system ui ;
 
: arrowhead ( L-system -- L-system )
    L-parser-dialect >>commands
    [ 60 >>angle ] >>turtle-values
    "XF" >>axiom
    {
        { "X" "YF+XF+Y" }
        { "Y" "XF-YF-X" }
    } >>rules ;
 
[ <L-system> arrowhead "Arrowhead" open-window ] with-ui