The optimal way of performing different side effects depending on whether the Validation is Success or Failure

Question

I expect the solution not to be based on the obvious pattern matching of if-else. I'm sure there should be more natural ways to do it, like combination of map and getOrElse on Option.

Answer 1

Validation有一种fold方法，可以选择产生副作用：

v.fold(e => println("Ouch, we got "+e), a => println("Yay!!  We got "+a))

Answer 2

Validation.fold

用字符填写答案......

Answer 3

For completeness, you may wish to operate on the Validation after side-effecting with it:

object Test {
  import scalaz._
  import syntax.bifunctor._
  import syntax.validation._
  def f(s: String) = { println(s"Err ${s}"); s }
  def g(i: Int) = { println(s"Int ${i}"); i }
  def m(x: Validation[String, Int]) = x bimap (f, g)
  def n(x: Validation[String, Int]) = f _ <-: x :-> g _
  def main(args: Array[String]) {
    val v = 17.success[String]
    val w = "nope".failure[Int]
    println(m(v) map (i => i + 1))
    println(m(v)); println(m(w))
    println(n(v)); println(n(w))
  }
}

Or, you maybe just like operators with faces. Do emoticonic operators have a name in the functional community? Given my present mood, I'd try emoperator, as in mope, but that may be too narrow. Or "lolop"? But a usage like x :-> f is clearly a "facial expression."