object session {
  import scala.math._
  println("Welcome to the Scala worksheet")       //> Welcome to the Scala worksheet

  def solve(a: Double, b: Double, c: Double): Any = {
    val pregroup = (b * b) - 4 * a * c
    if (pregroup < 0) {
      return null
    }
    val group = sqrt(pregroup)
    val end1 = (-b + group) / (2 * a)
    val end2 = (-b - group) / (2 * a)
    if (end1 == end2) {
      return end1
    }
    val endAll = (end1, end2)
    return endAll
  }                                               //> solve: (a: Double, b: Double, c: Double)Any

  solve(1.0, 6, 8)                                //> res0: Any = (-2.0,-4.0)
  solve(1, -8, 16)                                //> res1: Any = 4.0
  solve(1, 0, 16)                                 //> res2: Any = null

  def dist(a: (Double, Double), b: (Double, Double)): Double = {
    var (pairAA, pairAB) = a
    var (pairBA, pairBB) = b

    var halfA = (pairBA - pairAA) * (pairBA - pairAA)
    var halfB = (pairBB - pairAB) * (pairBB - pairAB)

    var end = sqrt(halfA + halfB)
    return end
  }                                               //> dist: (a: (Double, Double), b: (Double, Double))Double

  dist((1, 1), (0, 0))                            //> res3: Double = 1.4142135623730951
  dist((3, 0), (0, 0))                            //> res4: Double = 3.0

  def dot(a: (Double, Double, Double), b: (Double, Double, Double)): Double = {
    var (pairAA, pairAB, pairAC) = a
    var (pairBA, pairBB, pairBC) = b

    var end = pairAA * pairBA + pairAB * pairBB + pairAC * pairBC
    return end
  }                                               //> dot: (a: (Double, Double, Double), b: (Double, Double, Double))Double

  dot((2.0, 3, 4), (2, 2.0, 2))                   //> res5: Double = 18.0

  def force(a: Double, b: Double, c: Double): Double = {
    var g = 10
    return (g * a * b) / (c * c)
  }                                               //> force: (a: Double, b: Double, c: Double)Double

  force(10, 15, 10)                               //> res6: Double = 15.0

  def mean(a: Array[Double]): Double = {
    var i, total = 0.0
    for (x <- a) {
      total += x
    }
    return total / a.length
  }                                               //> mean: (a: Array[Double])Double

  mean(Array(2.0, 3, 4, 5))                       //> res7: Double = 3.5

  def stdDev(a: Array[Double]): Double = {
    var b = new Array[Double](a.length)
    var mean1 = mean(a)
    var i = 0
    for (i <- 0 to a.length - 1) {
      b(i) = (mean1 - a(i)) * (mean1 - a(i))
    }
    mean1 = mean(b)
    return sqrt(mean1)
  }                                               //> stdDev: (a: Array[Double])Double

  stdDev(Array(9, 2, 5, 4, 12, 7, 8, 11, 9, 3, 7, 4, 12, 5, 4, 10, 9, 6, 9, 4))
                                                  //> res8: Double = 2.9832867780352594

  def isPrime(a: Int): Boolean = {
    if (a < 3) return true
    var i = 0
    for (i <- 2 to a / 2) {
      if (a % i == 0) return false
    }
    return true
  }                                               //> isPrime: (a: Int)Boolean

  isPrime(0)                                      //> res9: Boolean = true
  isPrime(1)                                      //> res10: Boolean = true
  isPrime(11)                                     //> res11: Boolean = true
  isPrime(4)                                      //> res12: Boolean = false
  isPrime(5)                                      //> res13: Boolean = true

  def gcd(a: Int, b: Int): Int = {
    if (b == 0) a else gcd(b, a % b)
  }                                               //> gcd: (a: Int, b: Int)Int
  def phi(a: Int): Int = {
    var i, counter = 0
    for (i <- 1 to a - 1) {
            if (gcd(i,a) == 1) counter = counter + 1
    }
  return counter
  }                                               //> phi: (a: Int)Int

  phi(9)                                          //> res14: Int = 6
  phi(10)                                         //> res15: Int = 4

  def rollDice(): (Int, Int) = {
  var result = (0, 0)
  var generator = scala.util.Random
  var int1 = (abs(generator.nextInt() % 6)) + 1
  var int2 = (abs(generator.nextInt() % 6)) + 1
  return (int1, int2)
  }                                               //> rollDice: ()(Int, Int)

  rollDice                                        //> res16: (Int, Int) = (5,1)
  rollDice                                        //> res17: (Int, Int) = (4,6)
  rollDice                                        //> res18: (Int, Int) = (2,2)

}