Scala example source code file (List1.scala)

This example Scala source code file (List1.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

a, aa, boolean, boolean, cons, int, int, intlist, list, list, nil, nil, string

The Scala List1.scala source code

object lists {

  abstract class List[a] {
      def isEmpty: Boolean;
      def head: a;
      def tail: List[a];
      def prepend(x: a) = Cons[a](x, this);
  }

  def Nil[b] = new List[b] {
    def isEmpty: Boolean = true;
    def head = error("head of Nil");
    def tail = error("tail of Nil");
  }

  def Cons[c](x: c, xs: List[c]): List[c] = new List[c] {
    def isEmpty = false;
    def head = x;
    def tail = xs;
  } 

  def foo = {
    val intnil = Nil[Int];
    val intlist = intnil.prepend(1).prepend(1+1);
    val x: Int = intlist.head;
    val strnil = Nil[String];
    val strlist = strnil.prepend("A").prepend("AA");
    val y: String = strlist.head;
    ()
  }

  class IntList() extends List[Int] {
    def isEmpty: Boolean = false;
    def head: Int = 1;
    def foo: List[Int] { def isEmpty: Boolean; def head: Int; def tail: List[Int] } = Nil[Int];
    def tail0: List[Int] = foo.prepend(1).prepend(1+1);
    def tail: List[Int] = Nil[Int].prepend(1).prepend(1+1);
  }

  def foo2 = {
    val il1 = new IntList();
    val il2 = il1.prepend(1).prepend(2);
    ()
  }
}