Are you sure you meant "hash-ref!" and not just "hash-ref”?
Because even with (hash-ref! my-hash size (lambda () #f)), it would expect the #f to be of type (Listof String), which it isn’t. On Jun 27, 2014, at 3:32 PM, Manfred Lotz <[email protected]> wrote: > I tried this: > > #lang typed/racket/base > > (: my-hash (HashTable Nonnegative-Integer (Listof String))) > (define my-hash (make-hash)) > > > > (: my-hash-add (-> Nonnegative-Integer String Void)) > (define (my-hash-add size s) > (let* ([val (hash-ref! my-hash size #f)]) > (if val > (hash-set! my-hash size (cons s val)) > (hash-set! my-hash size (list s))))) > > and got: > > test.rkt:10:14: Type Checker: Polymorphic function `hash-ref!' could > not be applied to arguments: Argument 1: > Expected: (HashTable a b) > Given: (HashTable Nonnegative-Integer (Listof String)) > Argument 2: > Expected: a > Given: Nonnegative-Integer > Argument 3: > Expected: (-> b) > Given: False > > in: (hash-ref! my-hash size #f) > context...: > > /home/manfred/racket/share/pkgs/typed-racket-lib/typed-racket/typecheck/tc-toplevel.rkt:249:0: > type-check > /home/manfred/racket/share/pkgs/typed-racket-lib/typed-racket/tc-setup.rkt:40:0: > tc-setup > /home/manfred/racket/share/pkgs/typed-racket-lib/typed-racket/typed-racket.rkt:25:4 > standard-module-name-resolver > > > What can I do to make this work? > > > -- > Manfred > > > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
