I recommend doing the mutation yourself, and not using `shared`. That's the most obvious solution.
The reason that your `require/typed` doesn't work is that it creates new versions of the placeholder functions, but those aren't the ones that `shared` uses internally, so Typed Racket doesn't use the types you've given. Note also that the types you gave aren't safe -- the way shared uses placeholders expects particular types for particular ones (this would result in a contract error at runtime if `shared` used your bindings). Sam On Mon, Sep 29, 2014 at 12:10 PM, Konrad Hinsen <[email protected]> wrote: > Hi everyone, > > I am trying to port code creating a cyclic data structure to Typed > Racket, but notice that this is not as straightforward as I expected. > > Here is the untyped code I start from: > > #lang racket > > (struct foo (x) #:mutable) > (struct bar (x)) > > (define-values (f b) > (shared ([f (foo b)] > [b (bar f)]) > (values f b))) > > (eq? (bar-x b) f) > (eq? (foo-x f) b) > > Switching to Typed Racket and annotating the struct definitions, I get > an error message saying that make-placeholder and placeholder-set! > from racket/base are lacking type annotations. I also get the recommendation > to use require/typed for importing them. OK, let's try: > > #lang typed/racket > > (require/typed racket/base > [#:opaque Placeholder placeholder?] > [make-placeholder (-> Any Placeholder)] > [placeholder-set! (-> Placeholder Any Void)]) > > (struct foo ([x : bar]) #:mutable) > (struct bar ([x : foo])) > > (define-values (f b) > (shared ([f (foo b)] > [b (bar f)]) > (values f b))) > > (eq? (bar-x b) f) > (eq? (foo-x f) b) > > Same error message... which is not really surprising. I suppose typed/racket > already requires racket/base, so my additional require/typed has no effect. > But how can I fix this? I don't see any way to exclude items from > typed/racket. > > Konrad. > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
