Here's what Jay is trying to say: Welcome to Racket v6.1.1.6.
This works: > (define (none) (values)) > (let-values ([() (none)]) 42) 42 This doesn't: > (let-values ([(x) (none)]) 21) result arity mismatch; expected number of values not received expected: 1 received: 0 values...: context...: /Users/matthias/plt/racket/collects/racket/private/misc.rkt:87:7 [No, return arity mismatch isn't a particularly explanatory error message.] -- Matthias On Jan 6, 2015, at 6:56 AM, Jay McCarthy wrote: > They CAN return no values: (values) > > It is just awkward because you get an error in the binding forms if you try > to name the result (because there is none.) > > Jay > > On Monday, January 5, 2015, Jack Firth <[email protected]> wrote: > Given that racket has multiple return values, what sort of issues would arise > if functions were allowed to return no values at all instead of opting to > return the single value void when they have nothing to return? Is it purely a > backwards compatibility thing, or are there more fundamental problems with > that? > > On Mon, Jan 5, 2015 at 4:46 PM, Hendrik Boom <[email protected]> wrote: > 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 > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > > > > -- > Jay McCarthy > http://jeapostrophe.github.io > > "Wherefore, be not weary in well-doing, > for ye are laying the foundation of a great work. > And out of small things proceedeth that which is great." > - D&C 64:33 > ____________________ > Racket Users list: > http://lists.racket-lang.org/users
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