Task

Write a function/procedure/subroutine that is called with an integer value and returns the middle three digits of the integer if possible or a clear indication of an error if this is not possible.

Note: The order of the middle digits should be preserved.

Your function should be tested with the following values; the first line should return valid answers, those of the second line should return clear indications of an error:

123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345
1, 2, -1, -10, 2002, -2002, 0

Show your output on this page.




/** 
 * Optionally return the middle three digits of an integer.
 *
 * @example List(123,12345,-789,1234,12) flatMap (middleThree(_)), returns: List(123, 234, 789)
 */
def middleThree( s:Int ) : Option[Int] = s.abs.toString match {
  case v if v.length % 2 == 0   => None   // Middle three is undefined for even lengths
  case v if v.length < 3        => None
  case v                        => 			
    val i = (v.length / 2) - 1
    Some( v.substring(i,i+3).toInt )
}
 
 
// A little test...
val intVals = List(123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345,1,2,-1,-10,2002,-2002,0)
 
intVals map (middleThree(_)) map { 
  case None => "No middle three" 
  case Some(v) => "%03d".format(v)  // Format the value, force leading zeroes 
} mkString("\n")
 