rational example

class Rational(n: Int, d: Int) {
    require(d != 0)
    val numer = n
    val denum = d

    def this(n: Int) = this(n, 1)

    def + (r2: Rational): Rational =
        new Rational(
            numer * r2.denum + r2.numer * denum,
            denum * r2.denum
        )

    override def toString = numer + "/" + denum
}

val r1 = new Rational(2, 3)
val r2 = new Rational(3)
val r3 = r1 + r2
println(r1 + " + " + r2 + " = " + r3)