CompareFileNames.scala

def compareName(s1: String, s2: String): Int = {
  val n1 = s1.length
  val n2 = s2.length
  val min = math.min(n1, n2)
  var i = 0; while (i < min) {
    var c1 = s1.charAt(i)
    var c2 = s2.charAt(i)
    var d1 = Character.isDigit(c1)
    var d2 = Character.isDigit(c2)
    if (d1 && d2) {
      // Enter numerical comparison
      var c3, c4: Char = 'x'
      do {
        i += 1
        c3 = if (i < n1) s1.charAt(i) else 'x'
        c4 = if (i < n2) s2.charAt(i) else 'x'
        d1 = Character.isDigit(c3);
        d2 = Character.isDigit(c4);
      } while ( d1 && d2 && c3 == c4 )

      if (d1 != d2) return if (d1) 1 else -1
      if (c1 != c2) return c1 - c2
      if (c3 != c4) return c3 - c4
      i -= 1

    } else if (c1 != c2) {
      c1 = Character.toUpperCase(c1);
      c2 = Character.toUpperCase(c2);
      if (c1 != c2) {
        c1 = Character.toLowerCase(c1);
        c2 = Character.toLowerCase(c2);
        if (c1 != c2) {
          // No overflow because of numeric promotion
          return c1 - c2
        }
      }
    }
    i += 1
  }
  n1 - n2
}

assert(compareName("5", "5") == 0)
assert(compareName("5", "6") == -1)
assert(compareName("6", "5") == +1)
assert(compareName("x5", "x5") == 0)
assert(compareName("x5", "x6") == -1)
assert(compareName("x6", "x5") == +1)
assert(compareName("x5y", "x5y") == 0)
assert(compareName("x5y", "x6y") == -1)
assert(compareName("x6y", "x5y") == +1)
assert(compareName("5y", "5y") == 0)
assert(compareName("5y", "6y") == -1)
assert(compareName("6y", "5y") == +1)

assert(compareName("5", "51") == -1)
assert(compareName("51", "5") == +1)
assert(compareName("6", "51") == -1)
assert(compareName("51", "6") == +1)
assert(compareName("x5", "x51") == -1)
assert(compareName("x51", "x5") == +1)
assert(compareName("x6", "x51") == -1)
assert(compareName("x51", "x6") == +1)
assert(compareName("x5y", "x51y") == -1)
assert(compareName("x51y", "x5y") == +1)
assert(compareName("x6y", "x51y") == -1)
assert(compareName("x51y", "x6y") == +1)

this has a bug; fixed in ImperfectReconstruction > DifferenceProcess