Hi all,
when I try
for d in DyckWords(3):
print "--------------"
t = d.to_binary_tree()
s = t.left_rotate()
print ascii_art(t)
print ascii_art(s)
I get "IndexError: list index out of range".
What am I doing wrong?
The documentation of the left_rotate method starts with:
Left rotation on binary trees is defined as follows: Let T be a
binary tree such that the right child of the root of T is a node.
In the error happens when the following tree shows up:
sage: t
[[., [., .]], .]
sage: ascii_art(t)
o
/
o
\
o
So, indeed the right child of the root of t is not a node:
sage: ascii_art(t.left_rotate())
...
IndexError: list index out of range
sage: ascii_art(t.right_rotate())
o
\
o
/
o
I agree that the error could be more explicit.
What I find more misleading is the description in the docs: "Left rotation on binary trees is defined as follows:" I think it would be much better to say: "Left rotation is only defined for binary trees where the right child of the root is a node, as follows:"
Asked: 2016-08-26 10:26:24 +0100
Seen: 218 times
Last updated: Aug 26 '16
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