Dr. Thomas Fischbacher wrote:
> The OCaml manual gives no guarantee that Hashtbl.hash does not cons, so
> I cannot assume this.

Indeed, Hashtbl.hash can cons, but this does not contradict my point: 
its result does not depend on the physical location of objects in memory
(if it did, it would be impossible to use this function at all).

> Now, without that guarantee, there is a nasty race
> condition in which the determination of the hash bucket causes objects
> to move in memory.

Yes, objects can move in memory, but what is wrong with that? Their new 
hash value will remain the same.

-- Alain