added assignment 3 ex 2

src/Assignment3/IntSet.sc

@@ -2,6 +2,8 @@ abstract class IntSet() {
   def add(x: Int): IntSet
   def contains(x: Int): Boolean
   def foreach(f: Int => Unit): Unit
+  def union(other: IntSet): IntSet
+  def intersect(other: IntSet): IntSet
 }
 
 class NonEmpty(elem: Int, left: IntSet, right: IntSet) extends IntSet() {
@@ -23,6 +25,18 @@ class NonEmpty(elem: Int, left: IntSet, right: IntSet) extends IntSet() {
     f(elem)
     right.foreach(f)
   }
+
+  def union(other: IntSet): IntSet =
+    this.left.union(right)
+             .union(other)
+             .add(this.elem)
+
+  def intersect(other: IntSet): IntSet = {
+    val base = if (other.contains(this.elem)) Empty.add(this.elem)
+               else Empty
+    base.union(this.left.intersect(other))
+        .union(this.right.intersect(other))
+  }
 }
 
 object Empty extends IntSet() {
@@ -31,6 +45,8 @@ object Empty extends IntSet() {
   override def toString = "-"
 
   def foreach(f: Int => Unit): Unit = {}
+  def union(other: IntSet): IntSet = other
+  def intersect(other: IntSet): IntSet = Empty
 }
 
 val t1 = Empty
@@ -49,3 +65,7 @@ s.foreach(println)
 // 2, 3, 4, 7,
 // Because a BST is always sorted
 
+val s2 = Empty.add(3).add(4).add(6).add(2)
+
+s.union(s2)
+s.intersect(s2)