Thank you for the speedy fix, and thank goodness I'm not just crazy On Mon, Oct 20, 2014 at 2:45 PM, Vincent St-Amour <[email protected]> wrote:
> Thanks for the report! > > I pushed a fix earlier today. > > Vincent > > > > At Sun, 19 Oct 2014 23:16:11 -0700, > Jack Firth wrote: > > > > I think there may be a mistake in the type definition of foldl for the > case > > that accepts an initial value and three lists and a function of four > values > > to fold them over. The following untyped code runs correctly: > > > > #lang racket > > (define (f a b c d) d) > > (define ns '(0 1 2)) > > (define vs '(a 2 "b")) > > (foldl f 'ok ns ns vs) > > > > However, the typed form of this code gives a type error: > > > > #lang typed/racket > > (define: (f [a : Natural] [b : Natural] [c : Any] [d : Symbol]) : Symbol > d) > > (: ns (Listof Natural)) > > (define ns '(0 1 2)) > > (: vs (Listof Any)) > > (define vs '(a 2 "b")) > > (foldl f 'ok ns ns vs) > > > > Specifically, the type checker outputs: > > > > Type Checker: Polymorphic function `foldl' could not be applied to > arguments: > > Types: (-> a b c d d) d (Listof a) (Listof b) (Listof d) -> d > > (-> a b c c) c (Listof a) (Listof b) -> c > > (-> a b b) b (Listof a) -> b > > Arguments: (-> Nonnegative-Integer Nonnegative-Integer Any Symbol > > Symbol) 'ok (Listof Nonnegative-Integer) (Listof Nonnegative-Integer) > > (Listof Any) > > Expected result: AnyValues > > in: (foldl f (quote ok) ns ns vs) > > > > I think the issue may be in that first line of the type definition, (-> > a b > > c d d) d (Listof a) (Listof b) (Listof d) -> d. Shouldn’t that last > > argument type be (Listof c) instead of (Listof d)? > > > > [1.2 <text/html; UTF-8 (quoted-printable)>] > > > > [2 <text/plain; us-ascii (7bit)>] > > ____________________ > > Racket Users list: > > http://lists.racket-lang.org/users >
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