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Re: eql-specialized methods and before
- To: "Mark A. Tapia" <email@example.com>
- Subject: Re: eql-specialized methods and before
- From: kab (Kim Barrett)
- Date: Fri, 11 Feb 94 16:38:06 EST
- Cc: firstname.lastname@example.org, email@example.com
> From: "Mark A. Tapia" <firstname.lastname@example.org>
> Subject: Re: eql-specialized methods and before
> On Fri Feb 111994 Bob Hall writes:
> > Is the following a bug, or am I doing something wrong? It works okay
> > if I don't define the :BEFORE method.
> > (DEFMETHOD ZOG ((X (EQL :NORJ))) (print "Zognorj!"))
> > (DEFMETHOD ZOG ((X (EQL :BLID))) (PRINT "Zogblid!"))
> > (DEFMETHOD ZOG :BEFORE ((X T)) (PRINT "Before zog"))
> > (ZOG :NORJ)
> >> Error: No applicable primary methods for #<STANDARD-GENERIC-FUNCTION ZOG
> >> Applicable methods: (#<STANDARD-METHOD ZOG :BEFORE (T)>)
> >> While executing: CCL::%METHOD-COMBINATION-ERROR
> >> Type Command-. to abort.
> If you're going to use a before, after, or around methods (e.g.
> (defmethod zog :before ...
> (defmethod zog :after ...
> (defmethod zog :around ...
> you'll need to define a primary method The :before method is invoked before
> any other method, the after method after.
> The problems disappear if you add the following
> (defmethod zog ((x t))
> (declare (ignore x)
Actually, the behavior Bob Hall is seeing is in fact a bug, and there's a patch
for it. It's a bug because the two EQL specialized methods are both primary
methods. The relevant patch is a post 2.0p2 patch called
"eql-method-comb-patch". I'm not sure if this patch has been released or if you
will need to request it. In the meantime, the workaround of defining a method
on T might work in the particular application, though it might be better to make
the dummy default method to signal an error, since presumably it's never
supposed to actually be reached.