For comprehension over futures

gistfile1.scala

val f1 = future { 5 }
val f2 = future { "str" }
val f3 = (s: String) => future { s + "vap" }

val f4 = for {
  a <- f1
  b <- f2
  c <- f3(b)
} yield c * a

f4 onSuccess {
  case txt => println(txt)
}