Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!execu!sequoia!meritaus!dan
From: dan@meritaus.UUCP (Daniel Haug)
Newsgroups: comp.lang.lisp
Subject: Re: Question about Macros (Common Lisp)
Message-ID: <377@meritaus.UUCP>
Date: 5 Feb 90 16:48:17 GMT
References: <31480@shemp.CS.UCLA.EDU>
Distribution: usa
Organization: Merit Technology Austin Div.
Lines: 38

From article <31480@shemp.CS.UCLA.EDU>, by srt@maui.cs.ucla.edu (Scott Turner):
> 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))
> 
> Not what I expected.  What's happened?  Well, during the reading of the list 
> that forms the backquote structure in my macro, the reader found "*spec*" and
> turned that into an atom in the RULE package, hence rule::*spec*.
> 

If I were writing this, and wanted to have some lexical variables available
to the user of RULE, I would export these symbols from RULE.  Then the
user of the RULE system would either have to USE the RULE package, or
explicitly reference the variables with a RULE: prefix:

So, your rule system would define this:

  (in-package :rule)
  (export '(define *spec*) :rule)

and the user would do the following from his/her own package (a.k.a USER):

  (use-package :rule)
  (define some-rule ()
    (eql *SPEC* 'hyper)
    ...)

Also humbly offered...
-- 
dan haug
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