singletons VS containers

In Haskell, you can do this with various trickery involving GADTs/constraints/singletons.

Note that the list index operator has O(n) complexity. Ideally you'd want to use something like Seq from the containers package

Edison and containers both have sequence types that support efficient, cons, snoc, viewL, viewR, append, map, and length.

containers

Calling linked lists Haskell's "primary data structure" seems off-base to me. Yes, there's String, yes, there's built-in syntax for List... but there's also everything in containers, and vector is pretty easy to use in practice, though it would probably be good for more learning material to mention it more prominently.

Haskell has much more sophisticated immutable data structures, you can find them in the "containers" package: https://hackage.haskell.org/package/containers

I asked this on the libraries mailing list but thought posting here would bring in potentially more responses. I made a recent change to the behaviour of lookup and find (see here for more details: https://github.com/haskell/containers/pull/800).

Rust has nothing on Haskell. containers, which might as well be considered part of the standard library, has been out for almost 14 years and is still 0.x

When I was first learning I did a bunch of leetcode/codewars to get familiar with the containers library and GHCI repl workflow. Then using Real World Haskell as a reference I implemented a few coreutils to play with IO.