[jamwt]

I would say the two real barriers to writing effective Haskell projects are a.) "getting" monads, and b.) understanding the implications of laziness, especially with regard to space leaks and unconsumed thunks. Everything else isn't that big of a deal.

It's all much easier to digest, though, even for "really talented developers", if they have some experience with another functional language first. OCaml is a nice stepping stone before digging into the abstractions involved in understanding Haskell's powerful type system. Scala is good too, but having the object stuff mixed in there can lead you to rely on some patterns that aren't going to be available in a non-OOP language. I think the scheme/clojure path isn't bad either, but it's probably ideal to spend some time in the "statically typed" wing of the functional universe before going to Haskell.

[samstokes]

Could you say more about why "getting" monads was needed?

I came to Haskell with no understanding of monads, started writing code, and eventually used my knowledge of Haskell to learn about monads. Not understanding monads just meant I was lacking a useful design pattern, and found certain API docs confusing, but it didn't stop me from writing reasonable code in most circumstances.

On the other hand what you describe in your (awesome) blog post is a more significant Haskell project than any I've worked on, so I'd be interested to hear your experience.

I've not really written my own monad, or properly looked into monad transformer stacks, and I'm aware that I could probably clean up a lot of code using them - is that the sort of thing you mean?

[jamwt]

Sure, I can say more--put bluntly, and despite anything you might hear to the contrary, you basically do need to grok monads and monad transformers to tackle any nontrivial project in Haskell. Even if only to understand the code and APIs of libraries your application will interact with.

Basically, you can't swing a dead cat without hitting monads in the Haskell library ecosystem; therefore, you'll need to know what they are.

[mrshoe]

Catch phrase thief!

[jamwt]

You're just jealous I worked it in so naturally.

[grav1tas]

I agree. I dove into Haskell without doing any of the prior, and it was like running into a brick wall. However, persistence paid off in my case, but I do wonder how I would have handled it if I would have spent time with OCaml beforehand.