NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/comp/lang/scheme/2030

Internet Message Format | 1992-08-14 | 1.9 KB

Path: sparky!uunet!sun-barr!ames!agate!anarres.CS.Berkeley.EDU!bh
From: [e-mail] (Brian Harvey)
Newsgroups: comp.lang.scheme
Subject: Re: R^4RS Authors Comments on Dylan
Date: 14 Aug 1992 13:59:59 GMT
Organization: University of California at Berkeley
Lines: 28
Message-ID: <[e-mail]>
References: <[e-mail]>
NNTP-Posting-Host: anarres.cs.berkeley.edu

[e-mail] writes:
>o Dylan's use of generic functions, derived directly from CLOS, fit
>  into the language in a particularly elegant manner.  If the Scheme
>  community does decide to adopt a modest object system, we should
>  study Dylan's subset of CLOS to make an informed choice between this
>  approach and the more traditional object-dispatch mechanism.

As a teacher, I incline toward object-dispatch.  I know that the
generic function idea makes it easier to talk about an operation
that applies to more than one object (although not easier enough,
because of the combinatorial explosion of the number of possible
types of all the operands), but I think that for a learner the
whole idea of objects (smart data) is lost.  It's only in a very
attenuated sense that Dylan has objects at all, compared to how
I've learned to think about objects.  It just has data with
manifest type.

I know that the metaphor of asking an object to do something
doesn't make any difference in terms of the ability of the
language to get work done.  But I think it does make a difference
for the person learning the language; it gives rise to a very
different mental model.

I can see arguments on the other side, and maybe it's premature to
argue when there isn't even agreement on putting any kind of object
system in Scheme.  But I want to try to get educational concerns
into the picture, so that the eventual decision isn't made entirely
in terms of what's easy to implement efficiently and so on.