Re: (cond (else => display))

[Martin Grabmueller]

> From: Dirk Herrmann <address@hidden>
> Date: Sat, 13 Oct 2001 17:33:01 +0200 (MEST)
> 
> what should the result of (cond (else => display)) be?  Currently it is
> #t, which is because memoization transforms the else to #t.
> 
> IMO:
> 
> (define => 'foo)
> (cond (else =>))
>  --> 'foo
> (cond (else => display))
>  --> #<primitive-procedure display>
> 
> This would require to change the memoization not to transform the else to
> #t (in order to be able to distinguish it from a user given clause 
> (#t => display), and to change the evaluator accordingly.
> 
> Opinions?

I think that behind-the-scenes transformations which affect the
semantics of a syntactic form in a strange way (such as else => #t)
should be avoided.  In Sizzle, I had implemented it the way Dirk
suggests, but it will require an additional test/conditional jump in
the evaluator.  I think this is worth it and we should change it that
way, but other opinions are welcome.

Best regards,
  'martin