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- To: Robert.Frederking@CMU-CS-CAD.ARPA
- Subject: Painful retraction
- From: "David A. Moon" <Moon@SCRC-QUABBIN.ARPA>
- Date: Thu, 23 Aug 84 14:32 EDT
- Cc: guy.steele@CMU-CS-A.ARPA, common-lisp@SU-AI.ARPA, alan@MIT-MC.ARPA
- In-reply-to: <19188.8.131.52.25.12.Robert.Frederking@cmu-cs-cad.arpa>
Date: Thursday, 23 August 1984 11:34:34 EDT
I made the mental equivalent of a typo in my original question to
Guy Steele, thus inadvertantly slandering DEC.
What I meant to inquire about was that the *access functions* give
fatal errors if handed nil, which is a more reasonable behavior (if still
personally annoying). Thus, (ship-name nil) blows up, whereas I would
prefer it to just return nil. I.e., it would be nice if nil were the "null
structure", even though structures aren't (in VaxLisp) implemented as lists.
So, I'll make a corrected version of my original question: would it
be against the CommonLisp standard for an implementor to allow nils to pass
through the automatically-defined access functions, even if structures are
not implemented as lists? (A much less exciting question, I'm afraid.)
Sounds like a bad idea to me. And why single out NIL?
If this were done, it certainly should be an option to DEFSTRUCT that is not
turned on by default, because only specialized applications would want it, and
everyone else would prefer not to lose the error-checking.