//
// demo of some simple functions on arrays implemented with loops
//

import scala.io.StdIn._

// get array of doubles from stdin, prompting for size first
def readArray() : Array[Double] = {
  println("enter number of values")
  val sz = readInt
  val a = new Array[Double](sz)
  for (index <- 0 until sz) {
    println("next value?")
    a(index) = readDouble
  }
  a
}

// print array values 
def printArray(a:Array[Double]) {
  for (elem <- a) {
    println(elem)
  }
}

// reduction functions from array-demo rewritten to use loops

// approach from class, based on array-demo-2 version 
/*
def newSumArray(a:Array[Double]) : Double = {
  var sum = 0.0
  for (elem <- a) {
    sum += elem
  }
  sum
}
*/

// perform reduction on array elements 
// (returns "identity" if size of array is zero)
def combineArray(a:Array[Double], 
  combine:(Double,Double)=>Double, identity:Double
) : Double = 
{
  var result = identity
  for (elem <- a) {
    result = combine(result, elem)
  }
  result
}

// reduction functions from array-demo

def newSumArray(a:Array[Double]) : Double = {
  combineArray(a, _ + _, 0.0)
}

def newProductArray(a:Array[Double]) : Double = {
  combineArray(a, (x1,x2) => x1*x2, 1.0)
}

def newMaxArray(a:Array[Double]) : Double = {
  combineArray(a, (x1,x2) => x1 max x2, Double.MinValue)
}

def newMinArray(a:Array[Double]) : Double = {
  combineArray(a, (x1,x2) => x1 min x2, Double.MaxValue)
}