On: Roc Lang – Elm but for everywhere [video]

[fire_lake]

Can someone explain where Roc sits in terms of monads vs effects?

[chuckadams → fire_lake]

Firmly on the side of effects: Roc doesn’t have higher-kinded types, which makes it practically impossible to express monads. It’s covered somewhere in https://www.roc-lang.org/faq.html

[mjaniczek → chuckadams]

How do you need HKTs for monads?

[chuckadams → mjaniczek]

You need them to express a type constraint that’s generic for all monads. I might have gone a bit too far saying monads would be impossible without HKTs, but a single Monad type class would be, and you lose a lot of the power of monads if you don’t have that.

[fire_lake → chuckadams]

You can do monads without HKT but it is much more manual. You need to compose monad transformers yourself, for example.

[fourteenminutes → fire_lake]

Side effects are monadic (the main side-effectful abstraction, Task, is the continuation monad). There are no algebraic effects.

[postepowanieadm → fire_lake]

I don't have a PhD but I would say effects.