class Complex(val rp: Double, val ip: Double = 0):
  def +(other: Complex) = Complex(this.rp + other.rp, this.ip + other.ip)
  def unary_- = Complex(-rp, -ip)
  override def toString =
    var result = rp.toString
    if (ip != 0.0) result += " + " + ip + "i"
    result
  // etc.

given Conversion[Double, Complex] = Complex(_)
given Conversion[Int, Complex] = Complex(_)

object converts extends App {
  val c1 = Complex(3, 4)
  val c2 = Complex(5, 9)
  var c3 = c1 + c2
  println(c3) // 8.0 + 13.0i

  c3 = c1 + 5
  println(c3) // 8.0 + 4.0i

  c3 = 5.1 + c1
  println(c3) // 8.1 + 4.0i

  c3 = Complex(9)
  println(c3) // 9.0

  c3 = -c1
  println(c3) // -3.0 + -4.0i

}