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by jerf
348 days ago
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It can do it type-safely. Monad is a weird type that a lot of languages can't properly represent in their type system. However, if you do what dynamically-typed scripting languages do, you can do any fancy thing that Haskell does, because it is weakly typed in this sense. (The sense in which Python is "strongly typed" is a different one.) What you can't do is not do the things that Haskell blocks you from doing because it's type-unsafe, like, making sure that calling "bind" on a list returns a list and not a QT Window or an integer or something. |
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While true, a lot of FP-inspired libraries in the majority of languages that don't have HKT will just implement one or several specific monads as well as the common operations on them. This creates some redundancy and slight inconsistency, but often the shared vocabulary is still strong enough to carry around expectations more or less, even if it's not explicitly enforced by the type system. That's how you can have sequence(): List<Either<L,R>> -> Either<L, List<R>> in e.g. Kotlin, for example.
Even in Scala, where you actually can define a monad typeclass (trait), there are very popular libraries like ZIO that effectively give you a monad without actually adhering to any Monad trait. I believe they do this for type inference reasons.