I'm always curious when devs us efunctioal languages. How have you found Haskell for development?
A blast. All good things they say about Haskell are true and of the bad things, it's true it's harder to reason about low level optimization issues --- the only things I struggle with is finding occasional memory leaks that occur due laziness and predicting compiler optimizations and prodding the compiler to generate optimal assembly in the few places where it matters. Oh, and compilation with all optimizations turned on is slow (many minutes). so I need to use the fast compilation mode for development.
People also complain about IDE situation, but I wouldn't use it anyway, I'm happy with emacs. I could also complain about the size and speed of generated JavaScript, but actually it's a miracle I can generate JavaScript from a language designed to compile to native CPU code at all. And it's improving slowly.
IMHO, the only language that could be better suited for a CPU-intensive roguelike is Rust, but it's still less mature and it requires more diligence, more effort to write decent code (Haskell requires smarts and persistence when learning, but then the absence of 90% of bugs and the ease of refactoring gives it an edge in dev speed).
