On Wed, Oct 5, 2011 at 3:13 PM, Edward K. Ream <[email protected]> wrote:
> next = p.copy() if after and after == p.next() else after
>
> Yes, this is a hack, but it's a really great hack :-)
Well, it's not great yet. My first attempt at the undo failed with
this message::
badUnlink **can not happen: children[0] != p.v
We can fix this and clean up the code (make the hack official) this way:
next = p.nodeAfterTreeAfterDelete()
I just realized that nodeAfterTree should be called positionAfterTree,
but I digress :-)
The point is that the new method can create the proper position, with
the proper p.v, in a "relaxed" manner--it doesn't have to be a
one-liner. The name clarifies the code's intention. Much better
style.
I really like the new vnode-oriented approach. It may take a bit of
work to get right, but it should be worth it.
Ironically, the command simply appends a copy of each deleted
*position* to an undo list. That is, copying the position is the easy
way to get all the (vnode-oriented) undo information: parent_v is in
p.stack[-1], the vnode is p.v, and the childIndex is p._childIndex.
In short, all is going well :-)
Edward
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