[Chicken-users] New immediate values (was: DBI)

[Tobia Conforto]

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