object Polynomials
{

  class Poly(terms0: Map[Int, Double]) {
    def this(bindings: (Int, Double)*) = this(bindings.toMap)
    val terms = terms0 withDefaultValue 0.0

    def add (other: Poly) = new Poly(terms ++ (other.terms map adjust))

    def adjust(term: (Int, Double)): (Int, Double) = {
      val (exp, coeff) = term
      exp -> (coeff + terms(exp))
      // before adding defauld value
      /* terms get exp match { */
      /*   case Some(coeff1) => exp -> (coeff + coeff1) */
      /*   case None => exp -> coeff */
      /* } */
    }

    def + (other: Poly) = new Poly((other.terms foldLeft terms)(addTerm))

    def addTerm(terms: Map[Int, Double], term: (Int, Double)) = {
      val (exp, coeff) = term
      terms + (exp -> (coeff + terms(exp)))
    }

    override def toString =
      (for ((exp, coeff) <- terms.toList.sorted.reverse) yield coeff+"^"+exp) mkString " + "
  }

  def run = {
    println("Polynomials")
    /* val p1 = new Poly(Map(1 -> 2.0, 3 -> 4.0, 5 -> 6.2)) */
    /* val p2 = new Poly(Map(0 -> 3.0, 3 -> 7.0)) */
    val p1 = new Poly(1 -> 2.0, 3 -> 4.0, 5 -> 6.2)
    val p2 = new Poly(0 -> 3.0, 3 -> 7.0)
    println(p1.terms(7))
    println(p1)
    println(p2)
    println(p1 add p2)
    println(p1 + p2)
  }
}