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.




middleThree[n_Integer] :=
 Block[{digits = IntegerDigits[n], len},
  len = Length[digits];
  If[len < 3 || EvenQ[len], "number digits odd or less than 3", 
   len = Ceiling[len/2]; 
   StringJoin @@ (ToString /@ digits[[len - 1 ;; len + 1]])]]
 
testData = {123, 12345, 1234567, 987654321, 10001, -10001, -123, -100,
    100, -12345, 1, 2, -1, -10, 2002, -2002, 0};
 
Column[middleThree /@ testData]