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From: Dirk Herrmann <dirk@sallust.ida.ing.tu-bs.de>
Cc: Gary Houston <ghouston@arglist.com>,
	guile-devel@gnu.org, guile-user@gnu.org
Subject: Re: macros, procedure->macro
Date: Mon, 8 Jul 2002 22:23:22 +0200 (CEST)	[thread overview]
Message-ID: <Pine.GSO.4.05.10207082202540.12632-100000@sallust.ida.ing.tu-bs.de> (raw)
In-Reply-To: <87n0t376c9.fsf@zagadka.ping.de>

On 7 Jul 2002, Marius Vollmer wrote:

> Dirk Herrmann <dirk@sallust.ida.ing.tu-bs.de> writes:
> 
> > So what is so special about the uses of procedure->macro at the places
> > above?  
> >
> > [checking for redefinitions.]
> 
> We need to restrict this redefining behavior of 'define-class' et all
> to the top-level.  Local class definitions should not redefine classes
> outside of their scope (that would lead to a funny version of dynamic
> scoping of classes, eew), and redefinitions directly in one scope
> should be an error, just like any other definitions.

OK, I have changed the definitions of define-generic and define-accessor
to only show their re-defining behaviour if executed on top-level.  I also
changed all three (define-class, define-generic and define-accessor) to
use mmacros, which then would not change their behaviour at all.  Finally,
I changed define-class in stklos.scm to also use a mmacro, which is also
safe if no other 'define-class' code uses macros any more.

That means, after I have checked these changes in, guile itself will be
clean of using the built-in so called "macros", which are not really
macros in the scheme sense.

> Redefinitions on the top-level do make sense and can be supported by a
> normal macro via explicit module manipulations, i.e.
[...]

I am not sure I like the way, goops is based on names instead of objects
at a lot of places.  For example, it is not possible to do the following:
  (use-modules (oop goops))
  (define-generic G)
  (define (get-generic) G)
  (define-class <foo> () (x #:accessor (get-generic)))
because instead of a value, define-class expects a symbol after the
#:accessor keyword.

Automatic redefinition of classes is IMO a critical issue:
Redefinition of a class means to change the structure of all objects
of the class that already exist.  This should be a well considered
step and should not happen automatically (I am not even sure whether
it is a good idea at all).  It is not too inconvenient to request the user
to call class-redefinition instead of define-class.  It will inhibit
accidential redefinitions.

Just my opinion...

Best regards
Dirk Herrmann


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       reply	other threads:[~2002-07-08 20:23 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <87n0t376c9.fsf@zagadka.ping.de>
2002-07-08 20:23 ` Dirk Herrmann [this message]
2002-07-09 18:13   ` macros, procedure->macro Marius Vollmer
2002-07-10 21:54 ` Dirk Herrmann
2002-07-13  9:53   ` Dirk Herrmann
2002-07-13 18:38     ` Marius Vollmer
     [not found] <m3lm8e5o69.fsf@laruns.ossau.uklinux.net>
2002-07-14 21:35 ` Dirk Herrmann
2002-07-15 20:48   ` Marius Vollmer
2002-07-15 22:42   ` Neil Jerram
2002-07-16 22:00     ` Dirk Herrmann
     [not found] <200207012220.PAA08054@onyx.he.net>
2002-07-03 20:08 ` Dirk Herrmann
2002-07-04 20:16   ` Dirk Herrmann
2002-07-07 18:15     ` Marius Vollmer
2002-07-01 19:56 Dirk Herrmann
2002-07-01 21:30 ` Rob Browning
2002-07-03 20:24   ` Dirk Herrmann
2002-07-01 22:14 ` Marius Vollmer
2002-07-03 20:11   ` Dirk Herrmann
2002-07-07 17:54     ` Marius Vollmer
2002-07-08 20:31       ` Dirk Herrmann
2002-07-09 18:22         ` Marius Vollmer
2002-07-10  5:21           ` Dirk Herrmann
2002-07-10 19:31             ` Marius Vollmer
2002-07-10 19:57               ` Dirk Herrmann
2002-07-10 20:08                 ` Marius Vollmer
2002-07-01 22:17 ` Gary Houston
2002-07-09 21:16 ` Neil Jerram
2002-07-10  5:46   ` Dirk Herrmann
2002-07-10 10:15     ` Neil Jerram
2002-07-10 20:03       ` Dirk Herrmann
2002-07-13  0:09         ` Neil Jerram
2002-07-13  2:36           ` Clinton Ebadi
2002-07-14 15:23             ` Neil Jerram
2002-07-14 16:26               ` Marius Vollmer
2002-07-15  6:03                 ` Rob Browning
2002-07-13  6:53           ` Dirk Herrmann
2002-07-14 15:23             ` Neil Jerram

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