David Rush  <kumo@bellsouth.net> wrote:
+---------------
| Or perhaps more to the point in c.l.s, What can you say about
| the return value of
| 	(define (void) (if #f #f))
| Mostly, I'm curious about how the various implementations handle this
| value. So far I've looked at Scheme48, Bigloo, and Guile, and they all
| return a singleton value which is EQ? to itself.
+---------------

Add MzScheme to that list. It defines "void" as a primitive procedure,
gives most R5RS "unspecified" values -- such as (if #f #f) -- the
value "#<void>", and the top-level REPL suppresses printing the
result of an expression evaluation if the value is "#<void>" (hence
the need below for using "display" to print it):

	> void
	#<primitive:void>
	> (void)
	> (begin (display (void)) (newline))
	#<void>
	> (if #f #f)
	> (eq? (void) (if #f #f))
	#t
	> (define foo 123)
	> (set! foo 456)
	> (eq? (void) (set! foo 789))
	#t
	> foo
	789
	> 


-Rob

-----
Rob Warnock, 41L-955		rpw3@sgi.com
Applied Networking		http://reality.sgi.com/rpw3/
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