Using Scala 2.7.7:

If I have a list of Options, I can flatten them using a for-comprehension:

val listOfOptions = List(None, Some("hi"), None)
listOfOptions: List[Option[java.lang.String]] = List(None, Some(hi), None)

scala> for (opt <- listOfOptions; string <- opt) yield string
res0: List[java.lang.String] = List(hi)

I don't like this style, and would rather use a HOF. This attempt is too verbose to be acceptable:

scala> listOfOptions.flatMap(opt => if (opt.isDefined) Some(opt.get) else None)
res1: List[java.lang.String] = List(hi)

Intuitively I would have expected the following to work, but it doesn't:

scala> List.flatten(listOfOptions)
<console>:6: error: type mismatch;
 found   : List[Option[java.lang.String]]
 required: List[List[?]]
       List.flatten(listOfOptions)

Even the following seems like it should work, but doesn't:

scala> listOfOptions.flatMap(_: Option[String])
<console>:6: error: type mismatch;
 found   : Option[String]
 required: (Option[java.lang.String]) => Iterable[?]
       listOfOptions.flatMap(_: Option[String])
                          ^

The best I can come up with is:

scala> listOfOptions.flatMap(_.toList)         
res2: List[java.lang.String] = List(hi)

... but I would much rather not have to convert the option to a list. That seems clunky.

Any advice?