--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Fahad/Scala/Chapter6.sc	Sun Oct 26 16:42:28 2014 +0000
@@ -0,0 +1,68 @@
+package greeter
+
+object Chapter6 {
+  println("Classes and Objects")                  //> Classes and Objects
+
+  class Rational(n: Int, d: Int) {
+    private def gcd(x: Int, y: Int): Int = {
+      if (x == 0) y
+      else if (x < 0) gcd(-x, y)
+      else if (y < 0) -gcd(x, -y)
+      else gcd(y % x, x)
+    }
+    private val g = gcd(n, d)
+
+    val numer: Int = n / g
+    val denom: Int = d / g
+    def +(that: Rational) = new Rational(numer * that.denom + that.numer * denom, denom * that.denom)
+    def -(that: Rational) = new Rational(numer * that.denom - that.numer * denom, denom * that.denom)
+    def *(that: Rational) = new Rational(numer * that.numer, denom * that.denom)
+    def /(that: Rational) = new Rational(numer * that.denom, denom * that.numer)
+
+    //Inheritance and Overriding
+    override def toString = "" + numer + "/" + denom
+    //Parameterless Methods
+    def square = new Rational(numer * numer, denom * denom)
+  }
+  //Inheritance and Overriding
+  var i = 1                                       //> i  : Int = 1
+  var x = new Rational(0, 1)                      //> x  : greeter.Chapter6.Rational = 0/1
+  while (i <= 10) {
+    x += new Rational(1, i)
+    i += 1
+  }
+  println("" + x.numer + "/" + x.denom)           //> 7381/2520
+  //Parameterless Methods
+  val r = new Rational(3, 4)                      //> r  : greeter.Chapter6.Rational = 3/4
+  println(r.square)                               //> 9/16
+
+  //Abstract Classes
+  abstract class IntSet {
+    def incl(x: Int): IntSet
+    def contains(x: Int): Boolean
+  }
+
+  //Triats
+  trait IntSett {
+    def incl(x: Int): IntSet
+    def contains(x: Int): Boolean
+  }
+
+  //Implementing abstract class
+  class EmptySet extends IntSet {
+    def contains(x: Int): Boolean = false
+    def incl(x: Int): IntSet = new NonEmptySet(x, new EmptySet, new EmptySet)
+  }
+
+  class NonEmptySet(elem: Int, left: IntSet, right: IntSet) extends IntSet {
+    def contains(x: Int): Boolean =
+      if (x < elem) left contains x
+      else if (x > elem) right contains x
+      else true
+    def incl(x: Int): IntSet =
+      if (x < elem) new NonEmptySet(elem, left incl x, right)
+      else if (x > elem) new NonEmptySet(elem, left, right incl x)
+      else this
+  }
+
+}
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