Rational number

classes.scala

class Rational(n: Int, d: Int) {
  require(d != 0, "Denominator must be nonzero")

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

  private def gcd(a: Int, b: Int): Int =
    if (b == 0) a else gcd(b, a % b)

  private val g = gcd(n, d)
  val numer = n / g
  val denom = d / g

  def +(that: Rational) =
    new Rational(
      numer * that.denom + that.numer * denom,
      denom * that.denom)

  def -(that: Rational) =
    this + -that

  def unary_- = new Rational(-numer, denom)

  def <(that: Rational) =
    numer * that.denom < that.numer * denom

  def max(that: Rational) =
    if (this < that) that else this

  override def toString = numer + "/" + denom

  def toDouble = numer.toDouble / denom.toDouble
}

val x = new Rational(1, 3)
val y = new Rational(5, 7)
val z = new Rational(3, 2)
-x
x - y - z
y + y
x < y
x.max(y)
val r = new Rational(2)
x.toDouble
x + y