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Re: A mess with GOOPS

From: Panicz Maciej Godek
Subject: Re: A mess with GOOPS
Date: Mon, 5 Sep 2011 23:35:28 +0200

I've been trying to add the superclass.
Adding it to <vector> and <bytevector> turned out
to be extremely simple, but the problem emerged
when I was trying to generalize the <array> class.

The thing is that <array> is implemented as a smob,
and that there is no easy way to add a superclass
to a class created from smob.

I can think of a number of ways of making
a workaround, but all of them are nasty. Each
of them will require the modification of
goops.c: create_smob_classes.

The first way would be to check whether
!strcmp (SCM_SMOBNAME (i), "array")
and to behave appropriately when it happens.

But that would be just ugly.

The other two ways that come to my mind would be:
1. to modify the type `scm_smob_descriptor', adding
SCM supers; /* list of superclasses */

or, equivalently
2. to add a new global array,
SCM_API SCM smob_supers[MAX_SMOB_COUNT], such
that their default would either be SCM_EOL, or

The other idea would be to mess with
scm_sys_inherit_magic_x and add a superclass
after the creation of "<array>", but that doesn't
sound too sound (at least for as long as this action
is undocumented)

So to me it seems that adding the <generalized-array>
(or however should it be called) that would be the
ancestor of "array" requires some changes in the
guile API. I wouldn't do it without the overall approval.

Best regards

2011/9/3, Andy Wingo <address@hidden>:
> Hi Panicz,
> On Fri 02 Sep 2011 21:53, Panicz Maciej Godek <address@hidden>
> writes:
>> In other words, classes <vector>, <uvec> and <array> have nothing in
>> common, which requires me to triple the number of methods that could
>> accept any of these types.
> We should fix this.  We can probably do it in 2.0.  Interested in
> sending a patch?
> Currently this stuff is in C, unfortunately.  Perhaps it should move to
> Scheme at some point, but if you just wanted to add an <array> or
> <generalized-vector> superclass, see goops.c.  Look for the <uvec> stuff
> and follow the patterns.
> Andy
> --

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