Gregory Crosswhite
Or even better,
filter isJust
To make it worse again the original function can be generalized in a few ways. Here is a generalization from the inner Maybe type: import Data.Foldable as F catFoldables :: Foldable t => [t a] -> [a] catFoldables = concatMap F.toList Here is a generalization from the outer list type: joinMaybes :: (Alternative m, Monad m) => m (Maybe a) -> m a joinMaybes = (>>= maybe empty pure) And finally the generalization from everything: import Data.Foldable as F joinFoldables :: (Alternative m, Foldable t, Monad m) => m (t a) -> m a joinFoldables = (>>= F.foldr (\x _ -> pure x) empty) The final function looks a bit scary, but is actually surprisingly easy to understand, once you realize that 'foldr' is just a generalization of the 'maybe' function. The structure of Maybe is a list structure with at most one element after all. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/ -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/