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.




 
middle: procedure options (main);      /* 29 October 2013 */
   declare n fixed (15);
   declare s character (25) varying;
   declare in file input;
 
   open file (in) title ('/MIDDLE.DAT,type(text),recsize(100)');
   on endfile (in) stop;
 
   do forever;
      get file (in) list (n); put skip list (n);
      n = abs(n);
      s = trim(n);
      if length(s) < 3 then put list ('not possible');
      else  if mod(length(s), 2) = 0 then put list ('not possible');
      else
         do;
            do while (length(s) > 3);
               s = substr(s, 2, length(s)-2);
            end;
            put list ('The middle three digits are: ' || s);
         end;
   end;
 
end middle;
 