Summing up two options
scala, scala-collections, scala-option
Solution
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)
Problem
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 the following: Are there any intelligent way to sum them op using Scalas brilliant collection-methods? I realize that I could merge them into a collection, `flatten` it and use `reduceLeftOption` like so: ``` (one :: two :: Nil).flatten.reduceLeftOption(_ + _) // Some(3) ``` But, the solution above means creating a new collection, and living in a rich and developed world that takes time from all the other first world activities I might immerse myself into. And in a world where programming gets more and more luxurious for programmers like us, there must be one or more luxurious first world answer(s) to this, right? Edit: So to spell things out, here are some examples: If `one = Some(1)` and `two = Some(2)` we should have Some(3) If `one = Some(1)` and `two = None` we should have Some(1) If `one = None` and `two = Some(2)` we should have Some(2) If both `one` and `two` are `None` we should have None, since neither `one` or `two` can be summed correctly. Hope that clarified things :-)