Convert numbers to words, numbers up to thousands.

NumberToWords.scala

object NumberToWords {

  val units = List("one", "two", "three", "four",
    "five", "six", "seven", "eight", "nine")
  val teens = List("ten", "eleven", "twelve", "thirteen",
    "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen")
  val tens = List("twenty", "thirty", "forty",
    "fifty", "sixty", "seventy", "eighty", "ninety")

  def main(args: Array[String]) {
    //Solves Project Euler problem 17, http://projecteuler.net/problem=17
   println(Range(1, 1001).map((i: Int) => convert6(i).
      filterNot((p: Char) => p == ' ' | p == '-').length)
      .foldLeft(0)((m: Int, n: Int) => m + n))

    //To test: Range( 1, 1000).map((i:Int) => println(convert6(i)))
  }

  def digit(n: Int, b: Int) = {
    (n / b, n % b)
  }

  def convert2(n: Int): String = {
    val v = digit(n, 10)
    combine2(v._1, v._2)
  }

  def convert3(n: Int) = {
    val v = digit(n, 100)
    combine3(v._1, v._2)
  }

  def convert6(n: Int): String = {
    val v = digit(n, 1000)
    combine6(v._1, v._2)
  }

  def combine2(u: Int, v: Int): String = (u, v) match {
    case (0, v) => units(v - 1)
    case (1, v) => teens(v)
    case (u, 0) => tens(u - 2)
    case (u, v) => tens(u - 2) + "-" + units(v - 1)
  }

  def combine3(u: Int, v: Int) = (u, v) match {
    case (0, v) => convert2(v)
    case (u, 0) => units(u - 1) + " hundred"
    case (u, v) => units(u - 1) + " hundred and " + convert2(v)
  }

  def link(n: Int): String = n < 100 match {
    case true => " and "
    case false => " "
  }

  def combine6(u: Int, v: Int): String = (u, v) match {
    case (0, v) => convert3(v)
    case (u, 0) => convert3(u) + " thousand"
    case (u, v) => convert3(u) + " thousand" + link(v - 1) + convert3(v)
  }
}object NumberToWords {

  val units = List("one", "two", "three", "four",
    "five", "six", "seven", "eight", "nine")
  val teens = List("ten", "eleven", "twelve", "thirteen",
    "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen")
  val tens = List("twenty", "thirty", "forty",
    "fifty", "sixty", "seventy", "eighty", "ninety")

  def main(args: Array[String]) {
    val test = Range( 1, 10000)
    test.foreach((i:Int) => println(convert6(i)))
   }

  def digit(n: Int, b: Int) = {
    (n / b, n % b)
  }

  def convert2(n: Int): String = {
    val v = digit(n, 10)
    combine2(v._1, v._2)
  }

  def convert3(n: Int) = {
    val v = digit(n, 100)
    combine3(v._1, v._2)
  }

  def convert6(n: Int): String = {
    val v = digit(n, 1000)
    combine6(v._1, v._2)
  }

  def combine2(u: Int, v: Int): String = (u, v) match {
    case (0, v) => units(v - 1)
    case (1, v) => teens(v)
    case (u, 0) => tens(u - 2)
    case (u, v) => tens(u - 2) + "-" + units(v - 1)
  }

  def combine3(u: Int, v: Int) = (u, v) match {
    case (0, v) => convert2(v)
    case (u, 0) => units(u - 1) + " hundred"
    case (u, v) => units(u - 1) + " hundred and " + convert2(v)
  }

  def link(n: Int): String = n < 100 match {
    case true => " and "
    case false => " "
  }

  def combine6(u: Int, v: Int): String = (u, v) match {
    case (0, v) => convert3(v)
    case (u, 0) => convert3(u) + " thousand"
    case (u, v) => convert3(u) + " thousand" + link(v - 1) + convert3(v)
  }
}