Tree Algorithm

ian londonperlmongers at
Thu Dec 31 20:55:57 GMT 2009

Yes thats the ticket!

I especially like the description at the top of the first link.

'Nested sets rely on a demoralization of parts of the hierarchy'

There's probably something witty I could say about this concerning 
politics but I don't want to start a flame war!

'modified preorder tree traversal' is a bit of a mouthfull and I am not 
sure that 'nested sets' is the correct term either but at least the 
descriptions make sense.

Thanks for those links.

Now to create a module!


James Coupe wrote:
> ian <londonperlmongers at> wrote:
>> * Every node has a left and a right value and a level
>> * For any given node, all of it's descendents left values lie between
>> the nodes left and right values.
>> * For a leaf node, it's right value equals it's left value + 1
>> * All children of a parent will therefore be those with node numbers
>> between the parents left and right values and one level deeper.
> Nested Sets?
> Some discussion here, although without giving a proper name to the
> structure.

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