Why I get a () when I running my Scala code? - scala

Question

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.

Answer 1

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

Answer 2

You can do the following:
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)
Wrap result in a Either (You can think if it as Left = Failure and Right = Successful result)
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")
}
}
}