object test {
  def multBylarge(input: Array[Int]): Int = {
    var result=0
    var lst: List[Int]=List()
    if(input.length == 0) result =1
    else
      for(elements <- input) {
        lst = lst :  elements
      }
    var newlst = lst.sortWith(_ > _)
    result  = newlst(0) * newlst(1)
    result
  }

  def check2(input: Array[_]) = input.foreach {
    case _:Int => multBylarge(_)
    case _:Double => "this is a double array"
    case _:Float => "this is a float array"
    case _=> "this is not a value"
  }

  def main(args: Array[String]): Unit = {
      println(check2(Array(1,3,5,1,3,4)))
  }
}

this is my code, I just have no idea. It will be appreciated if anyone can help me with it. And I am not familiar with scala code, so if there has any other problem, please let me know.

CodePudding user response：

Scaladoc is your friend. foreach has return type of scala.Unit (see also) which has only one value - ():

def foreach[U](f: (T) => U): Unit

Apply f to each element for its side effects.

So actual signature of your method is def check2(input: Array[_]): Unit

CodePudding user response：

You can do the following:

1. Update check2 match on input rather then foreach (since multBylarge requires a array input anyway, foreach wouldn't work here since it iterates over every item in the array then tries to apply it to multBylarge)
2. Wrap result in a Either (You can think if it as Left = Failure and Right = Successful result)
3. Then match on the result in the main function to pretty print the result/error

object test {
  def multBylarge(input: Array[Int]): Int = {
    var result=0
    var lst: List[Int]=List()
    if(input.length == 0) result =1
    else
      for(elements <- input) {
        lst = lst :  elements
      }
    var newlst = lst.sortWith(_ > _)
    result  = newlst(0) * newlst(1)
    result
  }

  def check2(input: Array[_]): Either[String, Int] = input match {
      case ints: Array[Int] => Right(multBylarge(ints))
      case _: Array[Double] => Left("this is a double array")
      case _: Array[Float]  => Left("this is a float array")
      case _.               => Left("this is not a value")
    }

  def main(args: Array[String]): Unit = {
      check2(Array(1,3,5,1,3,4)) match {
       case Right(result) => println(s"Result is $result")
       case Left(error)   => println(s"Failed with $error")
    }
  }
}