Ninety-Nine Scala Problems: Problem 04 - Find the number of elements of a list.

Problem04.scala

// From: http://aperiodic.net/phil/scala/s-99/

// P04 (*) Find the number of elements of a list.
// Example:
// scala> length(List(1, 1, 2, 3, 5, 8))
// res0: Int = 6

object Problem04 {
  def main(args: Array[String]) {
    val values = List(1, 1, 2, 3, 5, 8)
    println(length(values))
  }

  // def length[T](values: List[T]): Int = 
  //   values match {
  //     case Nil      => 0
  //     case _ :: Nil => 1
  //     case _ :: xs  => 1 + length(xs)
  //   }

  def length[T](values: List[T]): Int = 
    lengthTail(0, values)

  def lengthTail[T](count: Int, values: List[T]) : Int = 
    values match {
      case Nil      => count
      case _ :: Nil => count + 1
      case _ :: xs  => lengthTail(count + 1, xs)
    }
}