Using Maybe type in Haskell

Solution 1:

Alternatively you can pattern match:

case maybeValue of
  Just value -> ...
  Nothing    -> ...

Solution 2:

You could use Data.Maybe.fromMaybe, which takes a Maybe a and a value to use if it is Nothing. You could use the unsafe Data.Maybe.fromJust, which will just crash if the value is Nothing. You likely want to keep things in Maybe. If you wanted to add an integer in a Maybe, you could do something like

f x = (+x) <$> Just 4

which is the same as

f x = fmap (+x) (Just 4)

f 3 will then be Just 7. (You can continue to chain additional computations in this manner.)