What is the type of `ops-hash` intended to be here? Sam
On Sat, Feb 9, 2013 at 9:27 PM, Neil Toronto <[email protected]> wrote: > I'd like to play around with implementing generics or type classes in Typed > Racket, but without changing its internals, just to see what it takes. I > think I could get something pretty decent working if I could get the > following program to type: > > > (define ops-hash (make-hasheq)) > > (: set-ring-ops! (All (A) (Symbol (ring-ops A) -> Void))) > (define (set-ring-ops! name ops) > (hash-set! ops-hash name ops)) > > (: get-ring-ops (All (A) ((ring-member A) -> (ring-ops A)))) > (define (get-ring-ops x) > (define name (ring-member-ops-name x)) > (hash-ref ops-hash name (λ () (error 'get-ring-ops > "unregistered ring ~a" > name)))) > > > Of course, I can't. In fact, I can't get this to work by writing > `set-ring-ops!' and `get-ring-ops' in untyped Racket and importing them > using `require/typed', because the contract system can't prove that the `A' > in `get-ring-ops' is the same as the `A' in `set-ring-ops!'. > > Is there a secret, hidden escape hatch that would allow me to get functions > with these types and behaviors? > > Neil ⊥ > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev _________________________ Racket Developers list: http://lists.racket-lang.org/dev
