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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