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    Date: 23 May 1983 1922-EDT (Monday)
    From: David.Dill@CMU-CS-A (L170DD60)
    I have been operating under the assumption
    that the only legitimate reason to do this is during debugging or
    development, to recover from a mistake in setting up a package or
    to "remove the back" from a package in order to poke around inside
    conveniently.  Does everyone else believe this (Moon in particular)?

Also to alter a package that has already been created in a suspended
environment, when it would be too expensive to re-create the suspended
environment from the ground up.  The terminal behind my back is connected
to a machine containing such an environment that was made more than
six months ago and would take a couple of weeks effort to reconstruct.

    If this is the case, then saying so in the manual could simplify some
    of the explanations of lookup rules, and also allow more flexibility
    in individual implementations (e.g. copy vs. search rules).
But it's important that no matter how it is implemented, and no matter
whether it is fast or slow, it works.  If the implementation has a separate
hash table for every package, and USE-PACKAGE makes entries in that hash
table, so that INTERN never does more than one hash lookup, then EXPORT
must make multiple hash insertions--one in every package on the
package-used-by list, except for those that shadow.