Circular structure printing

[Dave Dyer <DDYER at USC-ISIB>]

 I believe the Interlisp "HORRIBLEPRINT" package works as you
describe.  Interlisp's solution to the "problem" of having to do
two passes is that it only uses horribleprint where the user
has declared it necessary.  The code is common to all Interlisp
implementations, and is public domain as far as I know.
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