Not grandparent, but let me try. ML (Ocaml, I should say, because that's my experience) is like a functional C. As a production language, I'd recommend it high

Not grandparent, but let me try. ML (Ocaml, I should say, because that's my experience) is like a functional C. As a production language, I'd recommend it highly. It has excellent garbage collection. It generates blazingly fast native code. I can't speak either way about Haskell's use in production. I'm sure that many people have made it work. I just don't know how hard it is in practice. Haskell is lazy, for one, which makes it hard to reason about performance. You can have production memory leaks that are a bitch to debug. It also has a much more powerful, but also more complex type system. Explicit functors (Ocaml) are replaced by implicit type classes, which make the language more attractive (I'll grant that) but also make it easier to hang yourself by the monads. Haskell's still a great language, and there are a million things that recommend it. However, I don't see it as occupying the same space as the ML family. The main similarity is that both use Hindley-Milner type inference, but there are a lot of differences, too. Finally, Haskell is pure (except in the IO Monad, and a couple others) while Ocaml's not. You have stateful arrays and ref cells in Ocaml, and use them all the time when you're writing high-performance production code. In Haskell, any IO is to be done "in the IO monad" (which means, "in the context of evaluating an IO a", the latter being a thunk that does IO and returns an a.)