Hi all, I think I must be missing something about how Typed Racket predicates work. If I define a predicate for an instantiated polymorphic structure, my programs type check fine, but I get runtime errors when I try to use the predicate, which boil down to "expected procedure, given: #<make-contract>".
Here's a couple of examples: #lang typed/racket (struct: (A) poly ([n : A])) (define-type Foo (poly Integer)) (define-predicate foo? Foo) (: foo (Integer -> Foo)) (define (foo i) ((inst poly Integer) i)) ;; this type checks, but errors when evaluated ;(foo? (foo 3)) ; => procedure application: expected procedure, given: #<make-contract>; ; arguments were: #<poly> (define-type Bar (poly String)) (define-predicate bar? Bar) (: bar (String -> Bar)) (define (bar s) ((inst poly String) s)) (define: mixed : (Listof (U Foo Bar)) (list (foo 1) (bar "x") (foo -2) (bar "y"))) ;; this type checks, but errors if called (: filter-foos ((Listof (U Foo Bar)) -> (Listof Foo))) (define (filter-foos l) (filter foo? l)) ;(filter-foos mixed) ; => filter: expected argument of type <procedure (arity 1)>; given #<make-contract> So, what am I missing? Thanks, as always, Richard _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
