Re: goops proposal: proper struct classes

[Ludovic Courtès]

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’.