Now my example typechecks, but effectively I can't do anything with the function :-( so it is very unpractical
(: f ((Nothing -> Any) -> True)) (define (f g) #t) (f (lambda: ([x : Integer]) #t)) is there any way to make the typechecker happy, but being able to apply functions? For me, it would be something like: (: f ((Bottom -> True) -> True)) (define (f g) (g 1)) (f (lambda: ([x : Integer]) #t)) ?? or any other workaround? should I instead use an untyped module? Thanks 2011/11/28 Sam Tobin-Hochstadt <[email protected]> > On Mon, Nov 28, 2011 at 10:35 AM, Ismael Figueroa Palet > <[email protected]> wrote: > > As Any is supertype of all values, what is the equivalent type for > function > > types? > > > > (Any -> Any) does not work because of the contra-variant requirement of > the > > argument. > > > > (: f ((Any -> Any) -> True)) > > (define (f g) #t) > > > > (f (lambda (x) x) #t) ;; works > > (f (lambda: ([x : Integer]) #f)) ;; does not work > > > > The error is: > > > > Type Checker: Expected (Any -> Any), but got (Integer -> Any) in: > (lambda: > > ((x : Integer)) #f) > > > > If I understand it correctly, the type I'm looking for is (Bottom -> > Any), > > which satisfies the contra-variant and variant requirements for function > > subtyping. However, the Bottom type doesn't seem to exist (at least at > the > > user-level, because I remember seeing some error messages that mentioned > Top > > and Bottom). > > You're probably looking for the type `Nothing'. Note that functions > of type `(Nothing -> T)' are very hard to apply, though. > > -- > sam th > [email protected] > -- Ismael
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