//
// simple program to show, for list of grades, how many A's, B's, etc.
//
// this version uses map with a function that maps numeric grade to
// letter grade
//
// it also shows how to use collection methods to print in order
//
println("type in grades (integers), quit to end")
val grades = fillList()
val letterGrades = grades.map(g => numGradeToLetter(g))

val numA = count(letterGrades, 'A')
val numB = count(letterGrades, 'B')
val numC = count(letterGrades, 'C')
val numD = count(letterGrades, 'D')
val numF = count(letterGrades, 'F')

println(numA + " A")
println(numB + " B")
println(numC + " C")
println(numD + " D")
println(numF + " F")

println("max grade " + grades.max)
println("min grade " + grades.min)
println("avg grade " + grades.sum.toDouble/grades.length)
println("grades in order:")
grades.sorted.foreach(println(_))

def fillList() : List[Int] = {
  val input = readLine
  if (input == "quit")
    Nil
  else
    input.toInt::fillList()
}

// number grade to letter grade
def numGradeToLetter(num : Int) : Char = {
  if (num >= 90) 
    'A'
  else if (num >= 80)
    'B'
  else if (num >= 70)
    'C'
  else if (num >= 60)
    'D'
  else
    'F'
}

// count occurrences
def count(letterGrades : List[Char], c : Char) : Int = {
  letterGrades.count(g => (g == c))
}