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#+title: Challenge 135
#+date: 2021-10-22
#+html_link_up: ../
#+export_file_name: index
#+options: toc:nil
#+setupfile: ~/.emacs.d/org-templates/level-2.org
* Task 1 - Middle 3-digits
You are given an integer.
Write a script find out the middle 3-digits of the given integer, if
possible otherwise throw sensible error.
#+begin_src
Input: $n = 1234567
Output: 345
Input: $n = -123
Output: 123
Input: $n = 1
Output: too short
Input: $n = 10
Output: even number of digits
#+end_src
** Raku
Input's absolute value is taken because the sign is meaningless here. To
get middle 3-digits we take 3 digits from ~$n.chars div 2 - 1~ position,
~-1~ because Arrays are 0-indexed. It's guaranteed that we have odd number
of digits so ~div 2~ will land us on left of middle digit, we just take 3
digits from there.
#+begin_src raku
$n = abs $n;
die "too short" if $n.chars < 3;
die "even number of digits" if $n.chars %% 2;
put $n.substr($n.chars div 2 - 1, 3);
#+end_src
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