错误单位未接受参数scala

Question

How can I print the element of List after each iteration?

scala> def carry(c: Int, list: List[Int]):List[Int] = (c, list) match {
     |
     |   case (0, xs) => xs
     |
     |  case (1, Nil) => List(1)
     |
     |  case (1, x :: xs) => println(x,xs)((1 - x) :: carry(x, xs))
     |
     |   case (_, _) => throw new IllegalArgumentException("Invalid input!!!")
     |   }
<console>:18: error: Unit does not take parameters
        case (1, x :: xs) => println(x,xs)((1 - x) :: carry(x, xs))

Answer 1

your call to println(x, xs) returns a Unit type, and you're trying to call the return value with argument (1 - x) :: carry(x, xs) . Perhaps you already knew that. Curly braces are your friend here, as they create a contained expression. Here's the solution:

case (1, x :: xs) => {println(x, xs); (1 - x) :: carry(x, xs)}

or

case (1, x :: xs) => {
  println(x, xs)
  (1 - x) :: carry(x, xs)
}