On Friday, July 5, 2013 6:07:04 PM UTC-5, Edward K. Ream wrote:
> Happily, there is a simple strategy that sidesteps all the difficulties:
>
> Step 1. Verify, *before* making any changes to the outline, that all the
> positions passed to p.deletePositionsInList *initially* make sense.
>
> Step 2. Treat each position as a "request" to delete *some* vnode from the
> children array in the *position's* parent vnode.
>
And here is the corresponding code, with traces and asserts removed:
def deletePositionsInList (self,aList,callback=None):
c = self
# Verify all positions *before* altering the tree.
aList2 = [p for p in aList if c.positionExists(p)]
# Delete p.v, **if possible** for all positions p in aList2.
if callback:
for p in aList2:
callback(p)
else:
for p in aList2:
v = p.v
parent_v = p.stack[-1][0] if p.stack else c.hiddenRootNode
if v in parent_v.children:
childIndex = parent_v.children.index(v)
v._cutLink(childIndex,parent_v)
A slight complication: the code must call the low-level v._cutLink method
to properly remove v from parent_v.children.
This code passes the unit test that revealed the fatal problems with all
previous versions.
Edward
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