Flatten Scala Try

A little less verbose, and more type safe:

def sequence[T](xs : Seq[Try[T]]) : Try[Seq[T]] = (Try(Seq[T]()) /: xs) {
    (a, b) => a flatMap (c => b map (d => c :+ d))
}

Results:

sequence(l1)

res8: scala.util.Try[Seq[Int]] = Failure(java.lang.Exception: failed)

sequence(l2)

res9: scala.util.Try[Seq[Int]] = Success(List(1, 2, 3, 5, 6))

This is pretty close to minimal for fail-first operation:

def something[A](xs: Seq[Try[A]]) =
  Try(xs.map(_.get))

(to the point where you shouldn't bother creating a method; just use Try). If you want all the failures, a method is reasonable; I'd use an Either:

def something[A](xs: Seq[Try[A]]) =
  Try(Right(xs.map(_.get))).
  getOrElse(Left(xs.collect{ case Failure(t) => t }))