Summing up two options

Question

Let\'s say I have two optional Ints (both can be Some or None):

val one : Option[Int] = Some(1)
val two : Option[Int] = Some(2)

My question is

Answer 1

for (x <-one; y <- two) yield x+y

Or the less readable but strictly equivalent:

one.flatMap{x=>two.map(x+_)}

UPDATE: As your latest edit made quite clear, you only want a None as the result when both the input options are None. In this case I don't think you'll get anything better in terms of simplicity than what you already use. I could shorten it a bit but overall this is just the same:

(one ++ two).reduceOption(_ + _)

Answer 2

You could try this:

for( x <- one.orElse(Some(0)); y <- two.orElse(Some(0))) yield x+y

Answer 3

How about:

one.map(_ + two.getOrElse(0)).orElse(two)

Answer 4

obligatory scalaz answer is to use the scalaz Option monoid:

scala> one |+| two
res0: Option[Int] = Some(3)

It will do what you want with respect to None:

scala> two |+| None
res1: Option[Int] = Some(2)

scala> none[Int] |+| none[Int]
res2: Option[Int] = None

That none method is a method from scalaz which helps with type inference because instead of returning None <: Option[Nothing] it returns a Option[Int], there is a similar method from Some which returns an Option[A] for any given A instead of a Some[A]:

scala> 1.some |+| 2.some
res3: Option[Int] = Some(3)