In Scala how do you reference index in List of Serializable?-CodePudding

I'm new to Scala, actually learning it. I'm trying to combine multiple Lists and print a table by passing the list into a function. However when I try referencing values by index I get the error

Serializable does not take parameters

println("%3s%3s%3s\n".formatted(elm(0),elm(1),elm(2))) val list1 = List("1","2","3") val list2 = List("1","1","5")

var newLst = List[Serializable]()

newLst : = list1
newLst : = list2

def display_table(a:List[Serializable]){

  println("%3s%3s%3s\n".formatted("A","B","C"))
  for (elm <- a){
      println("%3s%3s%3s\n".formatted(elm(0),elm(1),elm(2)))
  }
}

display_table(newLst)

How what is the proper way of combining Lists of Lists and being able to iterate through them and reference them by index?

CodePudding user response：

The specific answer is that you don't have a List of Lists, you have a List of Serializables and you can't index into a Serializable.

But you don't need to index into the List to get the leading elements, just use match:

val list1 = List("1", "2", "3")
val list2 = List("1", "1", "5")
val newLst = List(list1, list2)

def display_table(a: List[List[String]]) = {
  println("  A  B  C")
  for (elm <- a) {
    elm match {
      case a :: b :: c :: _ =>
        println(f"$a%3s$b%3s$c%3s")
      case _ =>
        println("Not enough elements")
    }
  }
}

display_table(newLst)

Or use foreach directly rather than for:

def display_table(a: List[List[String]]) = {
  println("  A  B  C")
  a.foreach{
    case a :: b :: c :: _ =>
      println(f"$a%3s$b%3s$c%3s")
    case _ =>
      println("Not enough elements")
  }
}