Hmm no, I can’t say that I’ve ever writen code like that. For one, it might be better to use loop :: (a -> Either a b) -> a -> b instead so that you don’t have to sort through the result afterwards with find.

Lol. Yep, I'm a lame Haskeller.

I’m not sure exactly what you’re trying to do, but maybe using the State monad could be a good idea?

This is a pattern that has repeated on different things, and the main reason I haven't done much Haskell in the past couple years. Maybe State is what I need, I'll have to look into it.

If performance is critical you might be better of using a different language anyway (Haskell performance is okay but not amazing) but otherwise I don’t think that this is really gonna slow down your code unacceptably much.

See, I come from a maths background, and I have a bit of perfectionism going even if it's not a big deal. Maybe the processor can do a stupid thing and get away with it, but why should it?

What's that? Valuable programmer time you say? Pffft. I'll be over here designing a chess predicament with a multiply-infinite but well-defined solution to reach check (Yes, I've seen it done).