ROT13 implementation in Sass.

SassMeister-input.scss

// ----
// Sass (v3.3.8)
// Compass (v1.0.0.alpha.18)
// ----


// ROT13 implementation in Sass.
// https://en.wikipedia.org/wiki/ROT13

@function rot13($str) {
  $chars: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  $result: '';
  
  @for $i from 1 through str-length($str) {
    $char: str-slice($str, $i, $i);
    $index: str-index($chars, $char);
    $pos: 0;
    
    @if $index {
      // $index > 26 == Lower case
      // $index <= 26 == Upper case
      $start: if($index > 26, 27, 1);
      $pos: (($index - $start) + 13) % 26 + $start;
    }
    
    $result: $result + if($index, str-slice($chars, $pos, $pos), $char);
  }
  
  @return $result;
}

Test {
  $decoded: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  $encoded: 'NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm';
  
  encode: rot13($decoded) == $encoded;
  decode: rot13($encoded) == $decoded;
  chars: rot13('ifzTf45:;Kù^é(àçerijAhZg')
}

SassMeister-output.css

@charset "UTF-8";
Test {
  encode: true;
  decode: true;
  chars: "vsmGs45:;Xù^é(àçrevwNuMt";
}