FoldLeft examples

FoldLeft examples.scala

// Sum ints
def sum(ints: List[Int]): Int = ints.foldLeft(0)((a,b) => a + b)
def sum(ints:List[Int]): Int = ints.foldLeft(0)(_+_)


// find average from a list of Double
def average(list: List[Double]): Double =
  list.foldLeft(0.0)(_+_) / list.foldLeft(0.0)((r,c) => r+1)
 
def average(list: List[Double]): Double = list match {
  case head :: tail => tail.foldLeft( (head,1.0) )((r,c) =>
    ((r._1 + (c/r._2)) * r._2 / (r._2+1), r._2+1) )._1
  case Nil => NaN
}