Problem Statement

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: Show your output on this page.

Let's start with the solution:

def (mid3 n)
  withs (digits  (with outstring  # itoa
                   (pr abs.n))
         max  len.digits
         mid  (int max/2))
    if (and odd?.max (max >= 3))
      (digits mid-1 mid+2)