Q: sort's key and cmp parameters

[Paul Rubin]

Raymond Hettinger <python at rcn.com> writes:
> I'm not sure what you mean by this.  What are the semantics of
> sorting a tree?  Can you outline an example of tree that
> could be sorted easily with a cmp function but not a key function?

The idea was that you have a list of trees that you want to sort, and
an ordering relation between trees:

   def gt(tree1, tree2): ...

where you recursively descend both trees until you find an unequal
pair of nodes.  You're not trying to sort the nodes within a single
tree.