(define hilbert
'((to hilbert (size level parity)
(if (> level 0)
((left (* parity 90))
(hilbert size (- level 1) (- parity))
(forward size)
(right (* parity 90))
(hilbert size (- level 1) parity)
(forward size)
(hilbert size (- level 1) parity)
(right (* parity 90))
(forward size)
(hilbert size (- level 1) (- parity))
(left (* parity 90))
)
)
)
(hilbert 10 4 1)
))