Comments on Array Summary.

["Scott E. Fahlman" <Fahlman@CMU-CS-C.ARPA>]

I see no compelling reason to do array-copying when a previously
displaced array is undisplaced.  If you change displacement to a
different array you get new contents; by analogy, if you change
displacement to no existing array, it seems perfectly reasonable that
you would get a fresh array, observing :initial-contents or
:initial-element if they are specified, and with the default emptiness
otherwise.  What we want to do is handle this odd case without leaving
an ugly scar in the language, and it seems to me that this behavior is
no more surprising or illogical any other.  If people want to copy the
target array and displace to that, that is easy enough to do.

-- Scott