&REST

[Daniel L. Weinreb <DLW@ALDERAAN.SCRC.Symbolics.COM>]

    Date: 13 May 1987 1424-PDT (Wednesday)
    From: berman@vaxa.isi.edu (Richard Berman)
								 My feelings are
    that the above efficiency hack is a bug, even though it may be "supported by
    hardware".  

    Can anyone show me a valid justification for the above behavior?

There isn't any justification.  It's a bug.  It's among the list of
documented non-conformances of the Symbolics implementation, most of
which are a whole lot less severe than this one.  Unfortunately, it is
extremely difficult to fix without an unacceptable impairment of
performance in this implementation.  "No excuse, sir."