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Re: Class redefinition and class-changed.
- To: DUSSUD%Jenner%ti-csl.CSNet@relay.cs.net
- Subject: Re: Class redefinition and class-changed.
- From: Danny Bobrow <Bobrow.pa@Xerox.COM>
- Date: 24 Jul 87 08:48 PDT
- Cc: Bobrow.pa@Xerox.COM, common-lisp-object-system@SAIL.STANFORD.EDU
- In-reply-to: Patrick H Dussud <DUSSUD%Jenner@ti-csl.CSNET>'s message of Fri, 24 Jul 87 07:34:54 CDT
- Sender: Bobrow.pa@Xerox.COM
I think we should specify that instance updating will
not occur before the first method on an obsolete instance is
I see two problems with this approach:
- How would the environment guess that a class-changed method
will (or will not) be defined?
It doesn't have to guess. If the class changed method is defined before
any any method is called on an obsolete instance, it will be used.
Otherwise not. Hence users should define such class-changed methods
immediately (soon) after redefining the class.
- Even if you see it as an environment support, we need to
specify this support at the metaclass level since class
redefinition will be specified. I don't think we can afford to
leave holes like that in the metaclass protocol.
The meta-object support necessary is to provide a mechanism to obtain
the obsolete class so that class-changed methods can be defined, and to
specify when these methods can be defined in order to effect all
instances that need to be updated.