20 }

    20 }

    21 

    21 

    22 length_string_list(List("1", "2", "3", "4"))

    22 length_string_list(List("1", "2", "3", "4"))

    23 length_int_list(List(1, 2, 3, 4))

    23 length_int_list(List(1, 2, 3, 4))

    24 

    24 

    26 def length[A](lst: List[A]): Int = lst match {

    25 def length[A](lst: List[A]): Int = lst match {

    27   case Nil => 0

    26   case Nil => 0

    28   case x::xs => 1 + length(xs)

    27   case x::xs => 1 + length(xs)

    29 }

    28 }

    30 length(List("1", "2", "3", "4"))

    29 length(List("1", "2", "3", "4"))