Operator Overloading in Scala

OperatorOverloading.scala

package learn.scala

object OperatorOverloading {
  println("Welcome to the Scala worksheet")       //> Welcome to the Scala worksheet

  /**
   * We wish to use operators for rational number.
   * Example: r1 < r2 instead of using r1.less(r2)
   * This can be acheived in scala by understanding below two properties
   * a) Infix methods Notation
   * r1 less r2 is same as r1.less(r2)
   * b) Relaxed identifier
   * Scala does support relaxed idenifier names
   */
  class Rational(x: Int, y: Int) {
    def numer = x;
    def denom = y;

    /**
     * How about unary operators, lets try to expand definition of ++ operator
     * Format less definition from:
     * def less(r: Rational) = if (this.numer * r.denom < this.denom * r.numer) true else false
     */

    def <(r: Rational) = if (this.numer * r.denom < this.denom * r.numer) true else false

    /**
     * How about ++ operator, lets try to expand definition of ++ operator
     */
    def ++ : Rational = {
      val numer = this.numer + this.denom
      return new Rational(numer, this.denom)
    }

    /**
     * How about prefix unary operators, lets try to expand definition of by prefix unary - operator
     */
    def unary_- : Rational = new Rational(-this.numer, this.denom)

    override def toString() = this.numer + "/" + this.denom
  }

  val r1by2 = new Rational(1, 2)                  //> r1by2  : learn.scala.MethodInfix.Rational = 1/2
  val r3by4 = new Rational(3, 4)                  //> r3by4  : learn.scala.MethodInfix.Rational = 3/4
  // below are now valid expression now.
  r1by2 < r3by4                                   //> res0: Boolean = true
  -r1by2                                          //> res1: learn.scala.MethodInfix.Rational = -1/2
  r1by2++                                         //> res2: learn.scala.MethodInfix.Rational = 3/2
}