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;;; What I want is to be able to define two top-level flavors that
;;; differ *only* in a macro that is written in (or near) their
;;; respective base flavors. I.e. the macro expansion in an
;;; intermediate flavor should depend on *complete* definition of the
;;; top-level flavor.
;;; As an example considering the following:
;;; I have a FROB object which is an instance of a large, hairy
;;; flavor. It has an instance-variable SWITCH? that turn off parts
;;; of the functionality of the Frob. Now the stuff that this Switch
;;; affects is used all over the place, so I want it to be fast and
;;; clean (hence the macro).
;;; Basic Flavor that allows Switching.
(DEFFLAVOR BASIC-SWITCHABLE-FROB ((SWITCH?))
(DEFMETHOD (:SET-SWITCH BASIC-SWITCHABLE-FROB) (ON?)
(SETQ SWITCH? ON?))
(DEFMACRO-IN-FLAVOR (WHEN-SWITCH BASIC-SWITCHABLE-FROB) (&BODY BODY)
;;; Mid-level mixin that uses the Switch.
(DEFFLAVOR INTERMEDIATE-FROB-MIXIN ()
(DEFMETHOD (:FROBIZE INTERMEDIATE-FROB-MIXIN) ()
;;; Complete, usable FROB flavor (with Switch)
(DEFFLAVOR FULLBLOWN-SWITCHABLE-FROB ()
;;; OK; So far so good.
;;; Now, in certain applications of FROBS, I know that I will *never*
;;; want the Switch to be off and, because this is used a lot, I want
;;; to avoid the when-branch. In particular, I want to the
;;; WHEN-SWITCH macro to act as a No-op (i.e. so that I can leave its
;;; many calls in place).
;;; I.e., what I would *like* to be able to do is to define a
;;; base-flavor like the following:
(DEFFLAVOR BASIC-NON-SWITCHABLE-FROB ()
(DEFMACRO-IN-FLAVOR (WHEN-SWITCH BASIC-NON-SWITCHABLE-FROB) (&BODY BODY)
;;; This would allow me to write the non-switchable top-level flavor
;;; (which uses the common, intermediate flavor INTERMEDIATE-FROB-MIXIN).
(DEFFLAVOR FULLBLOWN-NON-SWITCHABLE-FROB ()
;;; But this loses because the WHEN-SWITCH in the :FROBIZE method gets
;;; the wrong macro definition. (Juggling the :REQUIRED-METHODS and
;;; changing the flavor dependencies just moves the basic problem
;;; somewhere else.)
;;; (Now, clearly this is a toy case, but for a real object I'd want
;;; the common intermediate mixins to call --some version of-- the
;;; WHEN-SWITCH macro, without their definitions being changed.)
;;; The only (brute-force) way I can figure to do this is to define
;;; two complete, parallel *identical* (except for their names) sets
;;; of mixins.