1 files changed, 63 insertions, 0 deletions
diff --git a/Lib/turtledemo/tree.py b/Lib/turtledemo/tree.py
new file mode 100644
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+++ b/Lib/turtledemo/tree.py
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+#!/usr/bin/env python3
+"""      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.getscreen().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()