There is a typed/json module in the snapshot build. But for that they just use ‘null instead of an arbitrary type.
On Jan 17, 2015, at 9:20 PM, Jordan Johnson <j...@fellowhuman.com> wrote: > Hi all, > > In playing with TR this evening, I found > >> (define-type (Foo A) >> (U A >> (List 'foo (Foo A)))) >> >> (define-predicate foo? Foo) > > generates the error “Type Foo could not be converted to a contract: cannot > generate contract for non-function polymorphic type”. I’ve read the page with > caveats about inference and polymorphic types, but since the example is about > using a function rather than defining a predicate, I’m not clear on how (if > at all) the technique could be adapted for this. > > (What I was actually doing, by the way, was seeing if I could port the JSON > library to TR. I ran into the problem of the null element being of arbitrary > type.) > > Best, > jmj > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
