16:27 <samth> skeemer: you would need to search on pkgs.racket-lang.org

21:14 <kengruven> i've got a function in typed/racket which takes Any, and does something of the form: (and (my-type? x) (fn-which-takes-my-type x)). how can i make this pass the type checker?

21:14 <kengruven> i tried simply wrapping the 2nd x with (cast x MyType), but it says "Unable to protect opaque type". i'm not sure what ann does (or how it's different from cast) but it doesn't seem to do anything here.

22:09 <samth> kengruven: is my-type? a predicate for your type?

22:12 <kengruven> samth: yes, but it's just a racket function. i just saw there's also a "make-predicate" in typed/racket and it's not clear if that's special to the type checker somehow.

22:12 <samth> kengruven: what is your type?

22:13 <samth> does the type checker know that my-type? and your type are connected in some way?

22:14 <kengruven> probably not? besides having a similar name, i don't know how to suggest to it that when this function returns #t, it's of that type.

22:16 <kengruven> i'm representing quaternions as math/array col-matrix of size 4. i've got (define-type Quaternion (Matrix Real)), and a function (quaternion? [q : Any]) : Boolean which also checks the size. i haven't figured out how to encode the size in the t/r Type.