Wow.

The idea of unique, stable node id's is interesting. If the tree is stored on a disk, then you maintain the mapping from id's to file offsets as an additional invariant, for example by using the node id as a btree key to the actual node contents. The big advantage is that clients don't have to worry about a node id ever changing.

I was recently looking at something where I might need this. Thanks, raph, for the links and adding the recent entries link.

(Can't say what. I might not do it and I don't want to get too many hopes up. ;-)