From ...
From: Erik Naggum <erik@naggum.no>
Subject: Re: What does this mean?  Error: Attempt to set the value of nil to nil.
Date: 1999/11/28
Message-ID: <3152777464420731@naggum.no>#1/1
X-Deja-AN: 554022909
References: <Pine.SOL.3.96L.991123052256.7930D-100000@titania.phil.cmu.edu> <ekv66ymg91r.fsf@lizard.pvv.ntnu.no>
mail-copies-to: never
X-Complaints-To: newsmaster@eunet.no
X-Trace: oslo-nntp.eunet.no 943788710 11027 195.0.192.66 (28 Nov 1999 11:31:50 GMT)
Organization: Naggum Software; +47 8800 8879 or +1 510 435 8604; fax: +47 2210 9077; http://www.naggum.no
NNTP-Posting-Date: 28 Nov 1999 11:31:50 GMT
Newsgroups: comp.lang.lisp

* Stig Hemmer <stig@pvv.ntnu.no>
| NIL is a constant.  It should not be changed.  The system isn't smart
| enough to see that you "change" it to the same value, NIL.

  that would be too smart for its own good.  it's the setting of a constant
  that is an error, not the value you attempt to set it to.  (the error
  message is thus a wee bit confusing in allowing that interpretation.)

#:Erik