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Generic interfaces Daphne Preston-Kendal (23 Jul 2021 11:34 UTC)
Re: Generic interfaces Lassi Kortela (23 Jul 2021 11:48 UTC)
Against hierarchy Lassi Kortela (23 Jul 2021 11:56 UTC)
Re: Against hierarchy Marc Nieper-Wißkirchen (23 Jul 2021 12:04 UTC)
Re: Against hierarchy Lassi Kortela (23 Jul 2021 12:08 UTC)
Re: Against hierarchy Marc Nieper-Wißkirchen (23 Jul 2021 12:26 UTC)
R6RS exception hierarchy Lassi Kortela (23 Jul 2021 12:39 UTC)
Re: R6RS exception hierarchy Marc Nieper-Wißkirchen (23 Jul 2021 13:09 UTC)
Re: R6RS exception hierarchy Lassi Kortela (23 Jul 2021 16:05 UTC)
Re: R6RS exception hierarchy Marc Nieper-Wißkirchen (23 Jul 2021 16:24 UTC)
Re: R6RS exception hierarchy Arthur A. Gleckler (23 Jul 2021 17:19 UTC)
Re: R6RS exception hierarchy Marc Nieper-Wißkirchen (23 Jul 2021 17:49 UTC)
Re: R6RS exception hierarchy Arthur A. Gleckler (23 Jul 2021 19:28 UTC)
Re: R6RS exception hierarchy John Cowan (26 Jul 2021 21:32 UTC)
Re: R6RS exception hierarchy Marc Nieper-Wißkirchen (27 Jul 2021 05:46 UTC)
Re: Generic interfaces Daphne Preston-Kendal (23 Jul 2021 17:47 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (23 Jul 2021 18:17 UTC)
Re: Generic interfaces Adam Nelson (23 Jul 2021 18:55 UTC)
Re: Generic interfaces Per Bothner (24 Jul 2021 19:31 UTC)
Re: Generic interfaces John Cowan (24 Jul 2021 04:27 UTC)
Re: Generic interfaces John Cowan (24 Jul 2021 04:26 UTC)
Re: Generic interfaces Daphne Preston-Kendal (25 Jul 2021 09:08 UTC)
Re: Generic interfaces Amirouche (25 Jul 2021 14:36 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (23 Jul 2021 12:18 UTC)
Re: Generic interfaces Daphne Preston-Kendal (23 Jul 2021 17:49 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (23 Jul 2021 17:51 UTC)
Re: Generic interfaces Daphne Preston-Kendal (23 Jul 2021 18:12 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (23 Jul 2021 18:39 UTC)
Re: Generic interfaces John Cowan (24 Jul 2021 03:56 UTC)
Re: Generic interfaces John Cowan (24 Jul 2021 02:22 UTC)
Re: Generic interfaces Jeremy Steward (24 Jul 2021 03:38 UTC)
Re: Generic interfaces Amirouche (25 Jul 2021 06:19 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (25 Jul 2021 08:39 UTC)
Re: Generic interfaces Daphne Preston-Kendal (25 Jul 2021 09:28 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (25 Jul 2021 10:04 UTC)
Re: Generic interfaces Daphne Preston-Kendal (25 Jul 2021 10:47 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (25 Jul 2021 12:16 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (29 Jul 2021 08:18 UTC)
Re: Generic interfaces John Cowan (26 Jul 2021 00:04 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (26 Jul 2021 06:25 UTC)
Re: Generic interfaces John Cowan (26 Jul 2021 12:26 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (26 Jul 2021 13:00 UTC)
Re: Generic interfaces Ray Dillinger (26 Jul 2021 19:28 UTC)
Re: Generic interfaces John Cowan (26 Jul 2021 19:53 UTC)
Re: Generic interfaces Arthur A. Gleckler (26 Jul 2021 22:15 UTC)
Re: Generic interfaces John Cowan (25 Jul 2021 23:37 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (26 Jul 2021 06:10 UTC)
Re: Generic interfaces John Cowan (26 Jul 2021 11:43 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (26 Jul 2021 12:09 UTC)
Re: Generic interfaces John Cowan (26 Jul 2021 13:14 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (26 Jul 2021 13:37 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (16 Nov 2021 18:52 UTC)
Re: Generic interfaces John Cowan (25 Jul 2021 23:00 UTC)
Re: Generic interfaces Marc Nieper-Wißkirchen (26 Jul 2021 05:44 UTC)

Re: Generic interfaces Daphne Preston-Kendal 23 Jul 2021 18:12 UTC

On 23 Jul 2021, at 19:51, Marc Nieper-Wißkirchen <xxxxxx@gmail.com> wrote:

> Can you explain this to me (a CL-noob)?

(type-of x) gives you a datum, in CL land usually a symbol, that tells you what kind of thing x is. That’s the name of a type, vaguely corresponding to a record-type descriptor in R6RS terms (but applicable to every object in the system, not just user-defined records).

If we had type-of in Scheme-land, we’d likely want to return type descriptors rather than symbols. But R7RS small has no real concept of type descriptors, except whatever the first argument to define-record-type is bound to. We have no type descriptors for lists, numbers, strings, etc. And crucially, there's no portable way in R7RS small, even in the case of record types, to get a record type descriptor from a record type instance. The only way to find out what type something is is to call predicates in turn until you get a #t answer.

This means you can’t portably implement polymorphic dispatch by storing type descriptors in a table (or similar) to avoid having to call every predicate in turn. This is also what I meant with Scheme generic functions being inherently incompatible with the CLOS/JVM/CLR approaches, which all use dispatch based on type descriptors (whatever those look like in the relevant runtimes) rather than predicates.

Daphne