A Maybe instance should have a map function (or equivalent)

[timbuckley]

Something wrapped in a maybe should have a .map() method, which takes a function that will be applied to x if that Maybe contains a Just x, or just pass along Nothing.

For example, in Haskell:

addOneOrNah :: Maybe Int -> Maybe Int
addOneOrNah maybeInt = fmap (+1) maybeInt

addOneOrNah Nothing
-- -> Nothing
addOneOrNah (Just 3)
-- -> Just 4