[r6rs-discuss] "Unspecified"

[Per Bothner]

Carl Eastlund wrote:
> I think "void" can still be a reasonable name, meaning "a value devoid
> of content", even if the meaning "no value here" isn't quite right.  I
> think "unit" can be confusing to anyone not brushed up on type theory,
> but everyone knows that "void" means some variation on "nothing".

Kawa has the literal #!void, and it is equivalent to (values) - i.e.
zero values.

There is actually one good reason to specify the semantics of
"unspecified", and that is to suppress printing:

#|kawa:1|# #!void
#|kawa:2|# (define x 10)
#|kawa:3|# x
10
#|kawa:4|# (if #f 3)
#|kawa:5|#

It is a niceity for a REPL to not print anything when the "value
to be printed" is #!void.
-- 
	--Per Bothner
per at bothner.com   http://per.bothner.com/