Path: utzoo!mnetor!uunet!husc6!hao!gatech!mcnc!decvax!ima!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: Structure editors in common lisp
Message-ID: <14165@think.UUCP>
Date: 22 Dec 87 19:58:38 GMT
References: <1487@orstcs.CS.ORST.EDU> <464@cresswell.quintus.UUCP> <215@aiva.ed.ac.uk>
Sender: usenet@think.UUCP
Reply-To: barmar@sauron.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge, MA
Lines: 34

In article <215@aiva.ed.ac.uk> jeff@uk.ac.ed.aiva (Jeff Dalton) writes:
>The book discusses the consistencey rules on page 173.  You will note
>that it specifies the conditions under which these rules remain true
>and the sorts of "explicit action" that can cause them to become false.

Unfortunately, these rules only exist when *PACKAGE* doesn't change.
This means that you can't maintain consistency if you use IN-PACKAGE.
And if you can't use IN-PACKAGE much of the value of the package
system is lost.

Here's an example.

file1 contains:
	(in-package "p1")
	(export 's1)

file2 contains:
	(in-package "p2" :use '("p1"))
	(setq s1 t)

CLtL says that the order of loading files shouldn't matter, but the
effect of the SETQ in file2 depends on whether file1 was loaded before
or after it.  If file1 is loaded first then it sets p1::s1; if file2
is loaded without loading file1 it sets p2::s1, and if file1 is later
loaded the EXPORT will signal an error because it would create a name
conflict.


---
Barry Margolin
Thinking Machines Corp.

barmar@think.com
seismo!think!barmar