Using Maybe type in Haskell

Question

I\'m trying to utilize the Maybe type in Haskell. I have a lookup for key, value tuples that returns a Maybe. How do I access the data that was wrapped by Maybe? For exam

Answer 1

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.)