Ndtyjky

I'm trying to implement an L-System generated Hilbert curve ,making use of python turtle graphics and recursion. My code seems to be working for the first two levels of recursion n=1 and n=2 but beyond that , the graphics just entangled (although I´m able to observe further modules within them), and I can´t seem to grasp what might be wrong here, do I need some intermediate steps to regenerate the Hilbert modules for deeper levels of recursion? Please see my code below , its relatively simple:

import turtle



def Hilbert_curve(A,rule,t,n):



    if n>=1:

        if rule:

            t.left(90)

            Hilbert_curve(A,not rule,t, n-1)

            t.forward(A)

            t.right(90)

            Hilbert_curve(A, rule,t, n-1)

            t.forward(A)

            Hilbert_curve(A,rule,t, n-1)

            t.right(90)

            t.forward(A)

            Hilbert_curve(A,not rule,t, n-1)

            t.left(90)

        else:

            t.right(90)

            Hilbert_curve(A,rule,t, n-1)

            t.forward(A)

            t.left(90)

            Hilbert_curve(A,not rule,t, n-1)

            t.forward(A)

            Hilbert_curve(A,not rule,t, n-1)

            t.left(90)

            t.forward(A)

            Hilbert_curve(A, rule,t, n-1)

            t.right(90)



def main():

    A=10

    t=turtle.Turtle()

    my_win=turtle.Screen()

    n=2

    rule=True

    Hilbert_curve(A,rule,t,n)

    my_win.exitonclick()



main()

Hilbert n=2

Hilbert n=3

The problem is with your else clause. The rule is already inverted coming in to the function, so you need to treat the rule the same as the then clause:

    else:

        t.right(90)

        Hilbert_curve(A, not rule, t, n - 1)

        t.forward(A)

        t.left(90)

        Hilbert_curve(A, rule, t, n - 1)

        t.forward(A)

        Hilbert_curve(A, rule, t, n - 1)

        t.left(90)

        t.forward(A)

        Hilbert_curve(A, not rule, t, n - 1)

        t.right(90)

However, if we change rule from a boolean to a number, parity, that's either 1 or -1, and then multiply parity by the angle, we can eliminate one of the two clauses of the orignal if statement:

from turtle import Screen, Turtle



def hilbert_curve(turtle, A, parity, n):



    if n < 1:

        return



    turtle.left(parity * 90)

    hilbert_curve(turtle, A, - parity, n - 1)

    turtle.forward(A)

    turtle.right(parity * 90)

    hilbert_curve(turtle, A, parity, n - 1)

    turtle.forward(A)

    hilbert_curve(turtle, A, parity, n - 1)

    turtle.right(parity * 90)

    turtle.forward(A)

    hilbert_curve(turtle, A, - parity, n - 1)

    turtle.left(parity * 90)



screen = Screen()



yertle = Turtle()

yertle.speed('fastest')  # because I have no patience



hilbert_curve(yertle, 10, 1, 4)



screen.exitonclick()