polynomial

package week6

object poly {

  class Poly(terms0: Map[Int, Double]) {
    val terms = terms0 withDefaultValue (0.0)
    def this(bindings: (Int,Double)*)= this(bindings.toMap)
    //def +(other: Poly): Poly = new Poly(terms ++ (other.terms map adjust))
    def +(other: Poly): Poly = new Poly((other.terms foldLeft (terms))(addTerm))

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

    def adjust(term: (Int, Double)): (Int, Double) = {
      val (exp, coef) = term
      exp -> (terms(exp) + coef) // possible with maos that have default value no more test necessary
      //terms get exp match {
      //case Some(coef1) => exp -> (coef + coef1)
      //case None        => exp -> coef
      //}
    }
    override def toString = (for ((exp, coef) <- terms.toList.sorted.reverse) yield coef + "x^" + exp) mkString " + "
  }

  val p1 = new Poly((1 -> 2.0), (3 -> 4.0), (5 -> 6.5))
                                                  //> p1  : week6.poly.Poly = 6.5x^5 + 4.0x^3 + 2.0x^1
  val p2 = new Poly((0 -> 5), (2 -> 8), (5 -> 8)) //> p2  : week6.poly.Poly = 8.0x^5 + 8.0x^2 + 5.0x^0
  p1 + p2


}