Entropy

func entropy(s) {
  var counts = Hash.new;
  s.each { |c| counts{c} := 0 ++ };
  var len = s.len;
  [0, counts.values.map {|count|
    var freq = count/len; freq * freq.log2 }...
  ]«-»;
}
 
say entropy("1223334444");

Output:

1.846439344671015493434197746305045223237