I think an easier to understand definition uses fmap and join. Example: f x = [x, x*2] f =<< [5, 3, 4] join (fmap f [5, 3, 4]) join ([[5, 10],

I think an easier to understand definition uses fmap and join. Example: f x = [x, x*2] f =<< [5, 3, 4] join (fmap f [5, 3, 4]) join ([[5, 10], [3, 6], [4, 8]]) [5, 10, 3, 6, 4, 8] So the pattern is fmap a function `a -> f b`; this leaves us with `f (f b)` so we flatten. You might notice that we could bind as often as we want since we always get a list of integers!