Re: [Haskell-cafe] There is no null; Maybe/Option types

On Fri, 22 Apr 2011, Christopher Done wrote:

Use of Fantom's save invoke and Maybe are more or less the same.

-- Hard way email = if userList /= Nothing            then let user = findUser "bob" (fromJust userList)                 in if user /= Nothing                       then getEmail (fromJust user)                       else Nothing            else Nothing

In idiomatic Haskell you would write case userList of Nothing -> Nothing Just plainUserList = let user = findUser "bob" plainUserList ... since (userList /= Nothing) requires an Eq instance without need and it requires fromJust. Or was there an educational purpose to write it with (/= Nothing) ?