I wrote recently about the option type specifically (called Maybe in Haskell): http://asivitz.com/posts/learn_to_love_maybe_kick_null http://asivitz.com/posts/l

I wrote recently about the option type specifically (called Maybe in Haskell): http://asivitz.com/posts/learn_to_love_maybe_kick_null http://asivitz.com/posts/learn_to_love_maybe_kick_null Swift has it, but it lets you easily subvert its meaning ('trust me, it's not null'), so I don't think it's as useful as it is in the usual functional languages.