Thanks, Sam -- Éric
On Nov 2, 2011, at 7:54 PM, Sam Tobin-Hochstadt wrote: > On Wed, Nov 2, 2011 at 12:56 PM, Eric Tanter <etan...@dcc.uchile.cl> wrote: >> Hi, >> >> Looking at the ICFP'10 paper on logical types, I tried the following: >> >> (: carnum? ((Pairof Any Any) -> Boolean : (Pairof Number Any))) >> (define (carnum? p) >> (number? (car p))) >> >> Type Checker: Expected result >> with filter (((Pairof Complex Any) @ p) | (! (Pairof Complex Any) @ p)), >> got filter ((Complex @ (car) p) | (! Complex @ (car) p)) >> in: (number? (car p)) >> >> To me, the filters seem to match, though. Any idea what is wrong here? > > What's going on here is that Typed Racket isn't smart enough to tell > that if it knows (car p) is Complex, then it should also know that p > is (Pairof Complex ...). This is something I've wanted to do for a > long time, but haven't gotten done yet. > >> I want to be able to use carnum? to discriminate <Number,Any> as in: > > The best thing to do here is to use `define-predicate': > > (define-predicate carnum? (Pairof Number Any)) > -- > sam th > sa...@ccs.neu.edu > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
