What language to learn after Haskell? [closed]

Answer 1

If you want a strong(er)ly typed Prolog, Mercury is an interesting choice. I've dabbled in it in the past and I liked the different perspective it gave me. It also has moded-ness (which parameters need to be free/fixed) and determinism (how many results are there?) in the type system.

Clean is very similar to Haskell, but has uniqueness typing, which are used as an alternative to Monads (more specifically, the IO monad). Uniqueness typing also does interesting stuff to working with arrays.

Answer 2

I'm a bit late but I see that no one has mentioned a couple of paradigms and related languages that can interest you for their high-level of abstraction and generality:

• rewriting systems, like Maude or ELAN;
• Constraint Handling Rules (CHR).

Answer 3

As you didn't mention any restrictions besides your subjective interests and emphasize 'rewarding to learn' (well, ok, I'll ignore the static typing restriction), I would suggest to learn a few languages of different paradigms, and preferably ones which are 'exemplary' for each of them.

• A Lisp dialect for the code-as-data/homoiconicity thing and because they are good, if not the best, examples of dynamic (more or less strict) functional programming languages
• Prolog as the predominant logic programming language
• Smalltalk as the one true OOP language (also interesting because of its usually extremely image-centric approach)
• maybe Erlang or Clojure if you are interested in languages forged for concurrent/parallel/distributed programming
• Forth for stack oriented programming
• (Haskell for strict functional statically typed lazy programming)

Especially Lisps (CL not as much as Scheme) and Prolog (and Haskell) embrace recursion.

Although I am not a guru in any of these languages, I did spend some time with each of them, except Erlang and Forth, and they all gave me eye-opening and interesting learning experiences, as each one approaches problem solving from a different angle.

So, though it may seem as if I ignored the part about your having no time to try a few languages, I rather think that time spent with any of these will not be wasted, and you should have a look at all of them.

Answer 4

I'd advise you learn Coq, which is a powerful proof assistant with syntax that will feel comfortable to the Haskell programmer. The cool thing about Coq is it can be extracted to other functional languages, including Haskell. There is even a package (Meldable-Heap) on Hackage that was written in Coq, had properties proven about its operation, then extracted to Haskell.

Another popular language that offers more power than Haskell is Agda - I don't know Agda beyond knowing it is dependently typed, on Hackage, and well respected by people I respect, but those are good enough reasons to me.

I wouldn't expect either of these to be easy. But if you know Haskell and want to move forward to a language that gives more power than the Haskell type system then they should be considered.

Answer 5

Go with one of the main streams. Given the resources available, future marketability of your skill, rich developer ecosystem I think you should start with either Java or C#.