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.




Educational Notes:
1) Array-style string manipulations (e.g. as = as[[1:]] ) always use bytes,
   not UTF-8 characters.  As digits and '-' are all ASCII, all is copacetic.
2) The task doesn't require 64-bit integer support, but I added it, dependant
   on whether the S-Lang library compile supports them, which it generally
   does.  [Main exception would be the current downloadable/installable MS-Win
   version of the Jed editor.]   
3) S-Lang functions peel arguments off right-to-left, opposite of many
   languages.  To align the order with other solutions, I enclosed the
   parameters in a list.  One alternative would have been for m3() to call
   _stk_reverse(_NARGS), then pop each arg directly off the stack.  Or of
   course just list the numbers backwards.
