Am Samstag, den 23.04.2016, 11:16 +0200 schrieb Christophe Raffalli:
> By the way what I really need is a hash function for arrays that I can
> update when I update one entry in the array.  Does anyone known of
> such a hash function ?

It would have to be commutative then (you need to remove the old version
and add the new one, for any element for the array). You could use XOR
or + of the hashes of the individual elements.

If this doesn't work good enough, I'd try to define larger hash blocks.
E.g. consider 4 consecutive elements as a block, and compute the hash of
the block, and take the XOR of all blocks you have. Quality depends a
little bit on what is in the elements.

Gerd
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Gerd Stolpmann, Darmstadt, Germany    gerd@gerd-stolpmann.de
My OCaml site:          http://www.camlcity.org
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Company homepage:       http://www.gerd-stolpmann.de
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