This version with `for/fold` works for me: (for/fold : (U Index #f) ([k : (U Index #f) #f]) ([i : Index (ann (in-range 5) (Sequenceof Index))]) i)
Sam On Sun, Jul 13, 2014 at 11:15 PM, Alexander D. Knauth <alexan...@knauth.org> wrote: > > On Jul 13, 2014, at 8:23 PM, Sam Tobin-Hochstadt <sa...@cs.indiana.edu> wrote: > >> Probably, what's going on here is that `for/last` has a hidden loop >> variable that starts off as `#f` and Typed Racket infers that to have >> type `False`. > > I thought that was the whole point of adding the : (U Index #f), right? To > provide a type for that loop variable? > >> >> If that's the case, there's nothing you can really do other than >> rewrite this as `for/fold`. > > Well, I tried to use for/fold, but it kept telling me to add more type > annotations even when I had annotated every > little thing that I could. > Then I tried reversing the sequences and using for/first (which would work > for what I’m doing but not in general), > but if I remember correctly that seemed to have the same problem. > Then I tried using the reversed sequences with for/or instead of for/first > and that worked fine. > But If there’s a hidden loop variable starting of as `#f`, then for/or should > have the same problem, but for/or works fine. > >> >> Sam >> >> On Sun, Jul 13, 2014 at 7:57 PM, Alexander D. Knauth >> <alexan...@knauth.org> wrote: >>> For some reason this: >>> (for/last : (U Index #f) >>> ([i : Index (ann (in-range 5) (Sequenceof Index))]) >>> i) >>> Is giving me this error: >>> . Type Checker: type mismatch >>> expected: False >>> given: Index in: (for/last : (U Index #f) ((i : Index (ann (in-range 5) >>> (Sequenceof Index)))) i) >>> >>> Why is it expecting False? >>> And is there some type annotation I can put somewhere to fix it or anything? >>> >>> >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users > ____________________ Racket Users list: http://lists.racket-lang.org/users
