Comment #1 on issue 738 by alexandr...(a)gmail.com: bugs in EyeSee
http://code.google.com/p/moose-technology/issues/detail?id=738
A plausible implementation of hash:
ESMalMatrix>>hash
^(self dimension hash bitXor: (self at: 1 and: 1) hash)
bitXor: (self at: self dimension x and: self dimension y) hash