make "factor 1/sqrt 2

to a :depth :size
    if :depth = 0 [forward :size stop]
    left 45
    a :depth-1 :size*:factor
    right 90
    b :depth-1 :size*:factor
    left 45
end

to b :depth :size
   if :depth = 0 [forward :size stop]
   a :depth-1 :size/2
   jump :size/2
   left 180
   a :depth-1 :size/2
   right 180
   jump :size/2
end

to jump :length
   penup
   forward :length
   pendown
end

to boundary :depth :size
   a :depth :size
   penup
   back :size
   pendown
   b :depth :size
end

to heighway :depth :size :parity
        if :depth = 0 [forward :size stop]
        left :parity*45
        heighway :depth-1 :size*:factor 1
        right :parity*90
        heighway :depth-1 :size*:factor (-1)
        left :parity*45
end

to heighway2 :depth :size
        if :depth = 0 [forward :size stop]
        left 45
        heighway2 :depth-1 :size*:factor
        right 90
        jump :size*:factor
        left 180
        heighway2 :depth-1 :size*:factor 
        right 180
        jump :size*:factor
        left 45
end