[Haskell-beginners] Idiomatic way of working with Either and lists

[Emmanuel Surleau]

Hi,

I'm trying to figure out the best way to work with Either and lists.

I have a function f which goes:

f :: a -> Either SomeError b

Now, I'd like to do:

applyF :: [a] -> (a -> Either SomeError b) -> Either SomeError [b]

That is, map f over a list and return either a list or the first error found.
The function should stop at the first error. I have implemented applyF with a
fold, but I'm sure there must be something like this already, being a fairly
generic pattern.

Thanks,

Emm