[jlturner]

I use F# daily, and to get around this limitation I use hacky custom code generation an F# script (fsx) to generated specific types.

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.

[danite]

Oh, for sure I still love monads. I miss Haskell's do syntax in every other language. I think it's a great design pattern that starts popping up constantly once you know where to look. My objection is being forced to use monads due to the language's lazy by default semantics. You get this problem with haskell where the IO monad eventually just pollutes a huge chunk of your code because you can't safely sequence side effects without it. Sometimes I just wanted an escape hatch that would let me do side effects that I knew to be safe/harmless. Haskell has unsafePerformIO but it truly is unsafe because you can't guarantee the execution order of your side effects, which makes it useless as an escape hatch for a lot of purposes.

[dean177]

Ocaml is getting something similar to ‘do’ syntax very soon (but for applicatives too!):

http://jobjo.github.io//2019/04/24/ocaml-has-some-new-shiny-...