[Python-Dev] gc ideas -- sparse memory (original) (raw)

Stephen J. Turnbull stephen at xemacs.org
Sun Dec 5 09:17:37 CET 2010

"Martin v. Löwis" writes:

Why is useful to expose an identity hash? AFAICS it is only useful in building an identity hash table. If so, why not just provide id() or the is operator or both and be done with it?

That's precisely James' point: Java provides the identity hash instead of the id() function (i.e. it does not have an equivalent of id()). Doing so gives greater liberties in implementing Java.

Yes, we understand that it makes the implementer's job easier. Why bother having an identity hash at all? Having taken away id() and provided maximum leisure to the implementer via

def identity_hash(object): return 42

is there any benefit left for the user/developer? All I see is costs: costs in implementation, costs in debugging. And AFAICS this is a problem that can be solved once and reused by everybody who needs id(); why does every developer need to write his own id() function?

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