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At Wed, 29 Oct 2003 08:25:39 -0600, scgmille@xxxxxxxxxxxxxxxxxx wrote:
>
> [1 <text/plain; us-ascii (quoted-printable)>]
> On Wed, Oct 29, 2003 at 03:12:27PM +0900, Alex Shinn wrote:
> > At Tue, 28 Oct 2003 21:37:26 -0600, scgmille@xxxxxxxxxxxxxxxxxx wrote:
> > You don't, however, need a full-blown, mother-of-all object systems for
> > this SRFI. You just need single-dispatch for an single-inheritance
> > hierarchy, which could be done in a very simple SRFI.
>
> I know. I note this in the Issues section, stating:
>
> "At the same time it is hoped that a future SRFI will specify a
> mechanism which will allow a portable and efficient implementation of
> collections to exist."
>
> I hope you'll agree that it is ultimately an implementation issue to get
> the dispatch right, but its not that difficult since it is a very simple
> form of dispatch. Bugs will exist in implementations of anything, they
> can be fixed.
True, it is very simple, which is why I think it would be better to
specify it clearly first. If you break things into small pieces there's
less confusion (and less to argue about).
A Scheme that implements this SRFI would end up using either their
native object system, a portable object system like TinyCLOS, or a
miniature dispatch system like bear suggested. I'm worried that these
are not semantically compatible. In the absence of a dispatch SRFI I'd
like to see the exact semantics specified in detail in SRFI-44 to avoid
future problems (and if it truly is simple then this will be a short
addition). Items that seem to need clarifying:
1) single vs. multiple inheritance
- just say single!
- if multiple, what CPL do you use?
2) single vs. multiple dispatch
- multiple is probably needed for *-union, etc.
- if multiple, how do you resolve conflicts?
3) abstract vs. concrete
- can concrete classes be sub-classed?
- can new abstract classes be made?
- can abstract classes sub-class concrete classes?
In the absence of these we don't have clear guidelines for extensions to
this SRFI, and future extensions are likely to have conflicts with each
other and/or specific implementations of the dispatch mechanism.
--
Alex