Nice OO Scala example for a talk for Harvey Nash

output.txt

5/3
5/3
1/3
4/9
true
10
true
false
List(2/3, 1, 10/7, 2)

Rational.scala

object Rational extends App {

  case class Rational(n: Int, d: Int=1) extends Ordered[Rational]{

    require(d != 0)
    private def gcd(a: Int, b: Int): Int = if (b == 0) a else gcd(b, a % b)
    private val g = gcd(n.abs, d.abs)
    val numer = n / g
    val denom = d / g
    def + (that: Rational) =  Rational( numer * that.denom + that.numer * denom,  denom * that.denom)
    def - (that: Rational) = Rational(numer * that.denom - that.numer * denom, denom * that.denom)
    def unary_- = Rational(-numer,denom)
    def * (that: Rational) = Rational(numer * that.numer, denom * that.denom)
    def / (that: Rational) = Rational(numer * that.denom, denom * that.numer)
    override def toString = if (denom==1) numer.toString else numer +"/"+ denom   
    def compare(that: Rational) = this.numer * that.denom - that.numer * this.denom
    def ==(that: Rational) = that.numer == numer && that.denom == denom
    def ==(that: Int):Boolean = this == Rational(that)
  }
  
  implicit def toRational(num: Int) = Rational(num)  
  
  val r2=Rational(2,3)
  println(1+r2)
  println(r2+1)
  println(-r2+1)
  println(r2*r2)
  println(Rational(10)==Rational(20,2))
  println(Rational(10))
  println (1>Rational(1,2))
  println (1>Rational(3,2))
  val list=List[Rational](1,2,Rational(2,3),Rational(10,7))
  println(list.sorted)
}