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Re: "fall-through" generic function args plus &context


From: Eric Abrahamsen
Subject: Re: "fall-through" generic function args plus &context
Date: Mon, 26 Dec 2016 14:48:08 -0800
User-agent: Gnus/5.130014 (Ma Gnus v0.14) Emacs/26.0.50 (gnu/linux)

Eric Abrahamsen <address@hidden> writes:

> I have a few defmethods that use the &context construct to dispatch on
> the value of major mode:
>
> (cl-defmethod my-make-buffer-name (&context (major-mode gnus-summary-mode))
>   ;; etc...
>   )
>
> I need a catch-all method, for default behavior when we're in other
> modes that aren't targeted by an existing method.
>
> I've tried things like:
>
> (&context _major-mode)
> (&context (major-mode t))
> (&context (major-mode nil))
> (&context (major-mode (eql _nuthin))
>
> And a few other things. Everything raises cl-no-applicable-method.
>
> What's the correct way to do this? Or do I need to override
> `cl-no-applicable-method' and catch the error?

Come to think of it, how does one override `cl-no-applicable-method' for
a specific generic? The defgeneric looks like:

(cl-defgeneric cl-no-applicable-method (generic &rest args)
  "Function called when a method call finds no applicable method."
  (signal 'cl-no-applicable-method `(,(cl--generic-name generic) ,@args)))

How do I specialize on "generic"?

Thanks,
Eric




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