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Re: goops proposal: proper struct classes
From: |
Ludovic Courtès |
Subject: |
Re: goops proposal: proper struct classes |
Date: |
Thu, 05 May 2011 18:35:54 +0200 |
User-agent: |
Gnus/5.110017 (No Gnus v0.17) Emacs/24.0.50 (gnu/linux) |
Hi Andy,
Andy Wingo <address@hidden> writes:
> If you know GOOPS, then you know that we have classes, rooted at
> <class>. And indeed <class> shows up a lot in documentation and in
> code. But that's not how it is in CLOS: our <class> corresponds to
> their `standard-class'. They have a superclass, called `class', which
> is the real root, and from which e.g. structure classes are derived.
>
> We need to do this. Currently, class-of on a struct/record data type
> gives a useless class that can't instantiate instances, doesn't know its
> slots, and does not reflect the vtable hierarchy.
Here’s an illustration:
--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (use-modules (oop goops) (srfi srfi-9))
scheme@(guile-user)> (define-record-type <foo> (make-foo x) foo? (x foo-x))
scheme@(guile-user)> (make-foo 2)
$3 = #<<foo> x: 2>
scheme@(guile-user)> (class-of $3)
$4 = #<<class> <> 148a4b0>
scheme@(guile-user)> (class-slots $4)
$5 = ()
scheme@(guile-user)> (class-of $4)
$6 = #<<class> <class> 8e7a50>
--8<---------------cut here---------------end--------------->8---
> So we need a <basic-class>, interposed between <class> and <object>,
> which will be the real root of our class meta-object hierarchy.
Why?
Couldn’t ‘scm_i_define_class_for_vtable’ build a full-blown class,
populating its CPL, its ‘slots’ slot, etc.?
Thanks,
Ludo’.