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From: | Tobia Conforto |
Subject: | [Chicken-users] New immediate values (was: DBI) |
Date: | Fri, 29 Feb 2008 01:31:38 +0100 |
Graham Fawcett wrote:
There does seem to be a good case for an immediate value that *can* be tested this way, though. John et. al. wouldn't have used (void) in eggs if there weren't.
What about providing a utility to create new immediate values, disjoint from anything else?
The immediate value space is far from cramped, if I'm not mistaken. Such a new-immediate-value function (which could benefit from a better name) would return a new value every time it's called, using for example an internal counter. One could write:
(define sql-null (new-immediate-value)) (define (sql-null? x) (eq? x sql-null))With the certainty that sql-null won't be eq? to anything else at all, won't be a list, a record, nothing at all except itself.
I think this could have a few uses. (Unless it's terribly broken in a way I can't see, which is quite possible :-)
Tobia
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