How would I implement a fixed size List in Scala?

Question

For example suppose I want a list that contains 0 up to a max of 1000 elements. Above this, the oldest insertions should be dropped first. Do collections support this functionality natively? If not how would I go about the implementation? I understand that certain operations are very slow on Lists so maybe I need a different data type?

Looking at an element should not affect the list. I would like insert and size operations only.

Answer 1

Here is my first pass implementation in case someone else find it useful

import scala.collection._
import mutable.ListBuffer

class FixedList[A](max: Int) extends Traversable[A] {

  val list: ListBuffer[A] = ListBuffer()

  def append(elem: A) {
    if (list.size == max) {
      list.trimStart(1)
    }
    list.append(elem)
  }

  def foreach[U](f: A => U) = list.foreach(f)

}