Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!usc!rutgers!njin!princeton!phoenix!eliot
From: eliot@phoenix.Princeton.EDU (Eliot Handelman)
Newsgroups: comp.lang.lisp
Subject: Re: Question about Macros (Common Lisp)
Message-ID: <13537@phoenix.Princeton.EDU>
Date: 3 Feb 90 08:09:39 GMT
References: <31480@shemp.CS.UCLA.EDU>
Reply-To: eliot@phoenix.Princeton.EDU (Eliot Handelman)
Distribution: usa
Organization: Princeton University, NJ
Lines: 33

In article <31480@shemp.CS.UCLA.EDU> srt@maui.cs.ucla.edu (Scott Turner) writes:
;
;	`(setf (structure-test foo)
;	       #'(lambda (*spec*) ,@test-part))
;
;Let's say that I define this macro in the RULE package.  Later on, I go to 
;use this in the USER package, and looking at the macro-expansion I see 
;this:
;
;	(lambda (rule::*spec*) (eql *spec* 'hyper))

Well, if *spec* is special, as I maybe was your intention from using the
stars, then you don't need the lambda list at all, so that's one solution.

A second is to let the rule specify its parameters, something like this:

(defmacro defrule (name params . test-part)
  `(setf (structure-test ',name)
	 #'(lambda ,params ,@test-part)))

Then you say:

(rule::defrule big-rule (x)
  (:test   (eql x 'foo))
  (:action (cons x 'foo)))

It might eventually be handy to generalize in this way, supposing you decide
that the rules are interested in more than one parameter.

Humbly offered,

--Eliot Handelman
  Princeton U., Music