[racket] Void expression found

On Mon, Jan 05, 2015 at 05:58:31PM -0500, Sean Kanaley wrote:
> I see "void" as a tangible value specifying no information, whereas
> "undefined" is literally no information. So void is more like an empty
> universe and undefined is no universe at all.

Algol 68 had a void value, called 'empty' in the defining report, but 
it didn't need a name in the language itself, because there were too 
many easy ways of geerating it.

I always considered void to be a type with exactly one value, which 
would need log2(1) bits to reprresent it, i.e., zero.

The report also left a number of things undefined.  An early draft of 
the report went on to specify 'undefined' as meaning anything from a 
reasonable continuation of the computation to 'indescribable chaos'.

-- hendrik