Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.8)
// Compass (v1.0.0.alpha.19)
// ----


// Frequency analysis
// https://en.wikipedia.org/wiki/Frequency_analysis


// Get char code from `$str` at `$index` in range [1-52][A-Za-z].
// ––––––––
// @param [string] $str
// @param [number] $index
// ––––––––
// @return [number]

@function char-code-at($str, $index: 1) {
  $chars: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  @return str-index($chars, str-slice($str, $index, $index));
}


// Get char at `$index` in range [1-52][A-Za-z].
// ––––––––
// @param [number] $index
// ––––––––
// @return [string]

@function from-char-code($index) {
  $chars: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  @return str-slice($chars, $index, $index);
}


// Relative frequencies of letters in the English language

$standard-frequency: (
  a: 8.2,  b: 1.5, c: 2.8, d: 4.3,
  e: 12.7, f: 2.2, g: 2.0, h: 6.1,
  i: 7.0,  j: 0.2, k: 0.8, l: 4.0,
  m: 2.4,  n: 6.7, o: 7.5, p: 1.9,
  q: 0.1,  r: 6.0, s: 6.3, t: 9.1,
  u: 2.8,  v: 1.0, w: 2.4, x: 0.2,
  y: 2.0,  z: 0.1
);

$standard-frequency-ordered: (
  e: 12.7, t: 9.1, a: 8.2, o: 7.5, 
  i: 7.0,  n: 6.7, s: 6.3, h: 6.1,  
  r: 6.0,  d: 4.3, l: 4.0, c: 2.8,  
  u: 2.8,  m: 2.4, w: 2.4, f: 2.2, 
  g: 2.0,  y: 2.0, p: 1.9, b: 1.5, 
  v: 1.0,  k: 0.8, j: 0.2, x: 0.2, 
  q: 0.1,  z: 0.1
);


@function get-frequency-table($str) {
  $frequency: ();
  $counter: ();
  $length: str-length($str);
  
  @for $i from 1 through 26 {
    $counter: map-merge($counter, (from-char-code($i + 26): 0));
  }
  
  @for $i from 1 through $length {
    $char: to-lower-case(str-slice($str, $i, $i));
    @if map-has-key($counter, $char) {
      $counter: map-merge($counter, ($char: map-get($counter, $char) + 1));
    }
  }
  
  @each $char, $count in $counter {
    $frequency: map-merge($frequency, ($char: $count / $length));
  }
 
  @return $frequency;
}


@function index-of-coincidence($frequency) {
  $idx: 0;
  
  @for $i from 1 through 26 {
    $c: from-char-code($i + 26);
    $idx: $idx + map-get($frequency, $c) * map-get($standard-frequency, $c);
  }
  
  @return $idx;
}


#{'frequency analysis'} {
  $str: 'In the first case, the cipher can be broken using the same techniques' 
      + 'as for a general simple substitution cipher, such as frequency analysis' 
      + 'or pattern words';
      
  $frequency: get-frequency-table($str);
  
  frequency: inspect($frequency);
  index: index-of-coincidence($frequency);
}

SassMeister-output.css

frequency analysis {
  frequency: ("a": 0.0641, "b": 0.01923, "c": 0.04487, "d": 0.00641, "e": 0.10897, "f": 0.01923, "g": 0.01282, "h": 0.04487, "i": 0.0641, "j": 0, "k": 0.00641, "l": 0.01923, "m": 0.01282, "n": 0.0641, "o": 0.03205, "p": 0.02564, "q": 0.01282, "r": 0.0641, "s": 0.08974, "t": 0.0641, "u": 0.03846, "v": 0, "w": 0.00641, "x": 0, "y": 0.01282, "z": 0);
  index: 5.39679;
}