On Fri, Dec 2, 2011 at 5:38 PM, Ismael Figueroa Palet <ifiguer...@gmail.com> wrote: > > > I'm trying to implement a function wrapper, that given any function returns > a function of the same type, but that maybe applies a different argument. So > far I haven't been successful, and based on previous questions to the mail > list it seemed that I needed to go to an untyped module because I couldn't > constraint values to a given type.
In general, I don't think that any solution is going to work here. You can't take arbitrary functions and apply them to specific arguments (such as the string "blabla") in a type-safe way. In you particular example, the function `f' is a constant function. But what if it expected `Integer' as its argument? Then your untyped code would be violating the type invariants. However, you can make your program work just by removing the parameterization over `A', and replacing that with `Any'. Then your program is safe, and your untyped module can safely call the function with any value it wants. However, you have to guarantee that the typed function can accept any kind of value (which `f' does, but other functions might not). As an additional note, the `CAST' operation you describe below, can't do exactly what you expect, because it's runtime semantics depends on how you instantiate `B'. But that would mean that you'd have to generate code for the `CAST' without knowing what `B' is. Typed Racket, like ML or Haskell, doesn't pass type parameters around as values, so you can't do this. > Module2 > #lang typed/racket > (struct: (A) T ([value : A])) > > (require/typed "untyped-wrap.rkt" > [untyped-wrap (Procedure Any -> (T Any))]) > (: wrap (All (A B) ((A -> (T B)) A -> (T B)))) > (define (wrap fun value) > [CAST (untyped-wrap fun value) (T B)]) > > (: f (Any -> (T One))) > (define (f x) (T 1)) -- sam th sa...@ccs.neu.edu _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
