On 3/24/20, mmcdan <mmcdani...@gmail.com> wrote: > Hello, > > I'm trying to use occurrence typing for (Vectorof Symbol) or (Boxof > Symbol). > > Creating a custom predicate for (Listof Symbol) seems to work: > --- > #lang typed/racket > > (: los? (-> Any Boolean : (Listof Symbol))) > (define los? > (lambda (seq) (and (list? seq) (andmap symbol? seq)))) > --- > > However I haven't been able to create one for vectors or boxes. None of the > things I've tried will typecheck. Any pointers?
Typed Racket can't be sure that untyped code won't change whats inside a mutable vector or box --- #lang racket (define v (vector 'A)) (define (set-v!) (vector-set! v 0 0)) (provide v set-v!) #lang typed/racket (require/typed "path-to-untyped.rkt" (v : (Vectorof Any)) (set-v! : (-> Void))) ;; suppose this worked (: vos (-> Any Boolean : (Vectorof Symbol))) (define (vos x) ....) (cond [(vos? v) ;; v : (Vectorof Symbol) (set-v!) ;; v now contains an integer! ....])) --- I don't know a work-around. I was hoping it could work for (Immutable-Vectorof Symbol), but I don't know what to use in place of `andmap`. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAFUu9R6nYVHoKCFGbjD8Q%2Bs__z2Cep9rwvqRL6HyZCE5GnzyhA%40mail.gmail.com.