Add types for indexes-of and indexes-where.

[NoahStoryM]

length just returns the length of a list, it should have nothing to do with the type of the list.

[capfredf]

I would say (All (a) (-> (Listof a) Index)) is 1. more accurate 2. in line with types for other list functions, though (-> (Listof Any) Index) won't be wrong for length. As to typed-untyped interaction, I need to sleep on it. By the way, do you have any programs that the polymorphic type gets in your way?

I'll take another look at the types for indexes-of and indexes-where later this week. Thanks

[NoahStoryM]

I think that length should be in line with types for length functions.

For example, I want to implement a generic function for finding the length of a data structure:

#lang typed/racket


(: make-length (All (A) [-> (pred A) [-> A Index] [-> Any * Index]]))
(define make-length
   (λ (pred len)
     (λ args
       (match args
         [`(,arg) #:when (pred arg) (len arg)]))))


(make-length bytes?  bytes-length)
(make-length string? string-length)
(make-length vector? vector-length)
(make-length list?   length)

Although that (inst length Any) can be used to solve the problem of this code, but I compared the types of length and vector-length, I can't get the meaning of defining length as a polymorphic type -- After all, it just returns the length of a list, it has nothing to do with the specific type of the list, I think this is also the reason why the argument type of vector-length is VectorTop.

[capfredf]

That seems a valid point. Note that in your example only vector and list are containers. Since length has been assumed to have a polymorhic type, for back -compatibility, I think we should keept it that way. (All (a) (-> (Listof Any) Index) looks a bit weird to me
a does not appear in the body and the whole type is actually mormorphic.

[NoahStoryM]

I also feel that (All (A) (-> (Listof Any) Index)) looks weird. I thought maybe TR will give warnings for these usages in the future, and eventually TR may no longer be compatible with them. So that (All (A) (-> (Listof Any) Index)) is a solution that allows me to avoid (inst length Any) now.

And it won't be a big problem for me to change the code back if that day comes. I agree to keep the current type of length.

[samth]

@capfredf are you ok with this now?

[capfredf]

lgtm