DigitSum.scala

object SumDigits {
  def main(args: Array[String]) {
    println("heelo [sic] world");
    sumDigits(94); //13
    sumDigits(32); //5
    sumDigits(44); //8
    sumDigits(5232); //12
    sumDigits(3535235); //26
    sumDigits(2147483647); //46 (Int [31 bit + 1 bit for sign] max value)
  }

  def sumDigits(arg: Int) {
    def absArg = scala.math.abs(arg); //As a precondition, I *could* say I only accept natural numbers. I could.

    var power: Long = 1; // All Int values accepted, power must go to 100000000000 (exceeds max Int value)
    var sizeArg = absArg % power; // 0

    // Accumulate our modulus operand [power] by measuring the results of increasing modulo ops
    while (sizeArg != absArg) {
      power = power * 10;
      sizeArg = absArg % power;
    }

    var digitSum: Int = 0;
    var argVar: Int = absArg;

    // Accumulate sum of digits
    while (power > 1) {
      // Get single-digit value from integer at [tens] place
      var digit = ((argVar - (argVar % power)) / power).toInt;
      digitSum = digitSum + digit;
      // Remove digit we just added to digitSum
      argVar = (argVar % power).toInt;
      // Go to next lower power of 10s
      power = power / 10;
    }

    // Add the last digit
    digitSum = digitSum + (arg % 10);

    printf("Sum of %d is %d\n", arg, digitSum);
  }
}