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Re: comment/question...

    On page 1-15 of the concepts draft of March 88 there is a
    statement that "...redefining a class may cause slots to be added
    or deleted.  If a class is redefined in such a way that the set of
    local slots accessible in an instance is the same and the order of
    slots in storage is unchanged, no instances are updated."

    Does this mean that if I change the :allocation of a slot from
    :instance to :class while leaving everything else about the class
    unchanged, that the existing instances of the class will keep their
    local slot values?
If you change the allocation of a slot from :instance to :class then the set of
local slots (those with allocation :instance) will be changed in all instances
of that class.  The default method for update-instance-for-redefined-class will
keep the local slot values for the remaining slots, but the slot whose
allocation has changed will have a new value computed for the class, and that
value will be the one accessible from each updated instance.