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Small omission in Chap 2
- To: Richard Fritzson <fritzson@PRC.Unisys.COM>
- Subject: Small omission in Chap 2
- From: Gregor.pa@Xerox.COM
- Date: Wed, 9 Mar 88 09:40 PST
- Cc: firstname.lastname@example.org
- Fcc: BD:>Gregor>mail>outgoing-mail-1.text
- In-reply-to: <8803091703.AA28687@bigburd.PRC.Unisys.COM>
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Date: 9 Mar 88 12:01 EST (Wednesday)
From: fritzson@PRC.Unisys.COM (Richard Fritzson)
The description of the standard-generic-function SLOT-MISSING
indicates that it is called when an attempt is made to access a
non-existent slot of an object, if the object's metaclass is
standard-class. This is a reasonable restriction (although I hate what
happens when I mistakenly apply an accessor function to NIL).
However, the description of the function SLOT-VALUE doesn't include
the restriction to objects whose metaclasses are standard-class. It
seems to say that slot-missing will always be called (even for objects
whose metaclass is built-in-class).
I expect that the former was the intended meaning, but they should
both say the same thing.
Thanks for catching this and sending us a message.
I believe the reason this bug happened in the document is that we tried
to finesse the issue that slot-value actually called the
generic-function slot-value-using-class. This means that we tried to
put too much of the description of the effect of calling slot-value in
the actual section on slot-value and got tripped up.
I suppose this will be easier to fix now that we actually have chapter
three and can feel free to reference it from chapter 2.