Is there a standard Haskell function like iterate that stops for Nothing?

Question

I am wondering if there is a standard function that iterates a function that returns a (Maybe value) over an initial value, collecting the values in a list, but ending the list when it gets to Nothing. This function can be implemented for example like so:

iterateMaybe f a = a : iterMaybe (f a) where
  iterMaybe Nothing = []
  iterMaybe (Just a) = a : iterMaybe (f a)

or slightly differently like so:

iterateMaybe' f Nothing = []
iterateMaybe' f (Just a) = a : iterateMaybe' f (f a)

None of the functions that Hoogle finds match.

Answer 1

It's a special case of unfoldr.

iterateMaybe f = unfoldr (fmap (\s -> (s,s)) . f)

The difference is list returned by unfoldr won't include the initial element.