Ian Bicking: the old part of his blog

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CLOS - the object system of Common Lisp - solved these update problems quite early on. You have many ways to update instances on the fly when classes change. Sure, it's not fully automatic - it can't be fully automatic. But it is very easy to do. Erlang goes even further. Of course that's because of it's primary use that _needs_ hotfixing.
Comment on PyCon and all that jazz
by Georg Bauer