Option monad is a great expressive way to deal with something-or-nothing things in Scala. But what if one needs to log a message when "nothing" occurs? According to the Scala API documentation, The Either type is often used as an alternative to scala.Option where Left represents failure (by convention) and Right is akin to Some...
instance Monad (Either a) where return = Left fail = Right Left x >>= f = f x Right x >>= _ = Right x this code frag in 'baby.hs' caused the horrible compilation error: Prelude> :l baby [1 of 1] Compiling Main ( baby.hs, interpreted ) baby.hs:2:18: Couldn't match expected type `a1' against inferred typ...
if a scala function is def A(): Either[Exception, ArrayBuffer[Int]] = { ... } what should be the right way to process the returned result? val a = A() and ? ...