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how to subtype a handle by contents of handle
- To: firstname.lastname@example.org
- Subject: how to subtype a handle by contents of handle
- From: email@example.com (Richard Lynch)
- Date: 26 Jul 1994 00:58:21 GMT
- Newsgroups: comp.lang.lisp.mcl
- Organization: ILS
Ok, maybe I'm just being stupid about how to do this, or maybe it's just
an inherently bad idea, but for some time now, I've been considering
writing a macro that do some fancy type-like stuff for handle-based data
Basically, I want to store a type-byte in the first byte of a handle, so I
want something like (def-datatype foo) to:
(defun foop (x)
(and (handlep x)
(>= (#_GetHandleSize x) 1)
(= (%hget-byte x) <auto-increment-counter>)))
(deftype foo '(satisfies foop))
Now I realize that there is a chance that some arbitrary handle [say a
PICT] would be misconstrued as a foo, but I'm not real worried about it.
I'm more interested in a good way to type-check among my own data-types.
My first attempts at writing def-datatype are failing miserably.
-- "TANSTAAFL" Rich firstname.lastname@example.org