jpayne@68: #!/usr/bin/env python3
jpayne@68: """      turtle-example-suite:
jpayne@68: 
jpayne@68:              tdemo_tree.py
jpayne@68: 
jpayne@68: Displays a 'breadth-first-tree' - in contrast
jpayne@68: to the classical Logo tree drawing programs,
jpayne@68: which use a depth-first-algorithm.
jpayne@68: 
jpayne@68: Uses:
jpayne@68: (1) a tree-generator, where the drawing is
jpayne@68: quasi the side-effect, whereas the generator
jpayne@68: always yields None.
jpayne@68: (2) Turtle-cloning: At each branching point
jpayne@68: the current pen is cloned. So in the end
jpayne@68: there are 1024 turtles.
jpayne@68: """
jpayne@68: from turtle import Turtle, mainloop
jpayne@68: from time import perf_counter as clock
jpayne@68: 
jpayne@68: def tree(plist, l, a, f):
jpayne@68:     """ plist is list of pens
jpayne@68:     l is length of branch
jpayne@68:     a is half of the angle between 2 branches
jpayne@68:     f is factor by which branch is shortened
jpayne@68:     from level to level."""
jpayne@68:     if l > 3:
jpayne@68:         lst = []
jpayne@68:         for p in plist:
jpayne@68:             p.forward(l)
jpayne@68:             q = p.clone()
jpayne@68:             p.left(a)
jpayne@68:             q.right(a)
jpayne@68:             lst.append(p)
jpayne@68:             lst.append(q)
jpayne@68:         for x in tree(lst, l*f, a, f):
jpayne@68:             yield None
jpayne@68: 
jpayne@68: def maketree():
jpayne@68:     p = Turtle()
jpayne@68:     p.setundobuffer(None)
jpayne@68:     p.hideturtle()
jpayne@68:     p.speed(0)
jpayne@68:     p.getscreen().tracer(30,0)
jpayne@68:     p.left(90)
jpayne@68:     p.penup()
jpayne@68:     p.forward(-210)
jpayne@68:     p.pendown()
jpayne@68:     t = tree([p], 200, 65, 0.6375)
jpayne@68:     for x in t:
jpayne@68:         pass
jpayne@68: 
jpayne@68: def main():
jpayne@68:     a=clock()
jpayne@68:     maketree()
jpayne@68:     b=clock()
jpayne@68:     return "done: %.2f sec." % (b-a)
jpayne@68: 
jpayne@68: if __name__ == "__main__":
jpayne@68:     msg = main()
jpayne@68:     print(msg)
jpayne@68:     mainloop()