cats either extensions 1

cats-either-extensions-1.scala

 def squareString(s: String, p: Int => Boolean): Either[String, Int] = {
    Either.fromTry( // Either from Try
      Try {
        val i = s.toInt
        i * i
      }
    ).leftMap { case _: NumberFormatException => "Boom - number format exception!" } // Left map
  }.ensure("result must not equal 9")(p) // Predicate to check with result satisfies a predicate

  val p: Int => Boolean = _ != 9

  squareString("2", p) // Right(4)
  squareString("2!", p) // Left(Boom - number format exception!!)
  squareString("3", p) // Left(must not equal 9)