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