#!/usr/bin/python

"""      turtle-example-suite:

             tdemo_tree.py

Displays a 'breadth-first-tree' - in contrast

to the classical Logo tree drawing programs,

which use a depth-first-algorithm.

Uses:

(1) a tree-generator, where the drawing is

quasi the side-effect, whereas the generator

always yields None.

(2) Turtle-cloning: At each branching point the

current pen is cloned. So in the end there

are 1024 turtles.

"""

from turtle import Turtle, mainloop

from time import clock

def tree(plist, l, a, f):

    """ plist is list of pens

    l is length of branch

    a is half of the angle between 2 branches

    f is factor by which branch is shortened

    from level to level."""

    if l > 3:

        lst = []

        for p in plist:

            p.forward(l)

            q = p.clone()

            p.left(a)

            q.right(a)

            lst.append(p)

            lst.append(q)

        for x in tree(lst, l*f, a, f):

            yield None

def maketree():

    p = Turtle()

    p.setundobuffer(None)

    p.hideturtle()

    p.speed(0)

    p.tracer(30,0)

    p.left(90)

    p.penup()

    p.forward(-210)

    p.pendown()

    t = tree([p], 200, 65, 0.6375)

    for x in t:

        pass

    print len(p.getscreen().turtles())

def main():

    a=clock()

    maketree()

    b=clock()

    return "done: %.2f sec." % (b-a)

if __name__ == "__main__":

    msg = main()

    print msg

    mainloop()