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: Wed, 10 Jul 2002 23:54:18 +0200 (CEST) [thread overview]
Message-ID: <Pine.GSO.4.05.10207102338290.16926-100000@sallust.ida.ing.tu-bs.de> (raw)
In-Reply-To: <87n0t376c9.fsf@zagadka.ping.de>
On 7 Jul 2002, Marius Vollmer wrote:
> 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.
>
> For example,
>
> (let ((foo (find-class "<moo>")))
> (define-class foo ...)
> ...)
>
> should not try to redefine the class that is the value of the location
> bound to foo by the let. It should simply shadow the outer foo.
Just a side note: define-class cannot be used other than on top-level.
The reason is, that define-class will define generic functions for
accessors that are not defined yet. Getting this right in non-top-level
scopes seems quite difficult (if not impossible) to do cleanly.
> Redefinitions on the top-level do make sense and can be supported by a
> normal macro via explicit module manipulations, i.e.
>
> (define-class foo ...)
> =>
> (module-define-class (current-module) 'foo ...)
>
> with
>
> (define (module-define-class mod sym ...)
> (let* ((var (module-ensure-local-variable! mod 'foo))
> (class (make-class ...)))
> (if (variable-bound? var)
> (redefine-class (variable-ref var) class))
> (variable-set! var class)))
I am currently changing the definition of define-class accordingly.
However, I am not sure which of the following solutions to choose:
* use a helper function module-define-class. This would have to be
exported. And, it could not be used like define-class, since you
would not be able to pass an empty combination for an empty list
of supers: (module-define-class some-module some-name () ...)
would not be allowed, since you would have to quote the ().
* use a helper macro module-define-class. This would have to be
exported as syntax.
* change the expanded code of define-class to hold all necessary
instructions to do the module manipulations. In this case, the
mmacro would return the following:
`(begin
;; define accessors
,@(pre-definitions (slots exp) env)
;; update the current-module
(let ((class (class ,@(cddr exp) #:name ',name)))
(let* ((var (module-ensure-local-variable!
(current-module) ',name))
(old (and (variable-bound? var)
(variable-ref var))))
(if (and old
(is-a? old <class>)
(memq <object> (class-precedence-list old)))
(variable-set! var (class-redefinition old class))
(variable-set! var class))))))))))))
Which solution should be used? I will try to update define-generic and
define-accessor accordingly.
Best regards,
Dirk Herrmann
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next prev parent reply other threads:[~2002-07-10 21:54 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 ` macros, procedure->macro Dirk Herrmann
2002-07-09 18:13 ` Marius Vollmer
2002-07-10 21:54 ` Dirk Herrmann [this message]
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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