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:

: middle3
| s sz |
   abs asString dup ->s size ->sz
   sz 3 <    ifTrue: [ "Too short" println return ]
   sz isEven ifTrue: [ "Not odd number of digits" println return ]
   sz 3 - 2 / 1+  dup 2 + s extract ;