Additionally, on cases where you’re not specifying the data of the type itself, you can use static type constraints on members. This doesn’t give you a default implementation like Haskell but you can always provide one as a function.
Btw the monadic threading is still very useful, especially when mixing impure code and mutation (when appropriate). The async and result monads, in F# computation expression form, are particularly useful.
For a good example of async + impure code, check out MailboxProcessor, which is part of the standard F# lib. Works similar to CSP/goroutine + channels/actor models; makes parallelized concurrency and message passing easy. You can also make pure mailboxes easily by recursively passing data forward, but sometimes you don’t want to for memory / gc & alloc reasons.