4 ms·

Or just: fn (Just q) (Just z) = q + z fn _ _ = 0

• brabel 9y ago
  Wouldn't this let me call `fn true false` or `fn "hi" 2`? Or the second declaration takes the inferred type of the arguments from the first one?
  • andolanra 9y ago
    This isn't two functions: it's actually one function defined by cases. You can think of it as equivalent to fn x y = case (x, y) of (Just q, Just z) -> q + z (_, _) -> 0 but the case becomes implicit in the repetition of the function name at the top level of indentation.
    • dllthomas 9y ago
      > at the top level of indentation At the same level, really - it works in a let or a where as well.
• masklinn 9y ago
  Surely since you have monads you can just use the tools they give you? fn = liftM2 (+)
  • zenhack 9y ago
    That doesn't do quite the same thing; the original example gets rid of the Maybe, defaulting to 0.
    • masklinn 9y ago
      > That doesn't do quite the same thing You're missing the point entirely. > the original example gets rid of the Maybe, defaulting to 0. http://hackage.haskell.org/package/base-4.10.1.0/docs/Data-Maybe.html#v:fromMaybe http://hackage.haskell.org/package/base-4.10.1.0/docs/Data-M...