anchor.diff:      var stepsLeft = steps;
       while (steps > 0) {
         _selection();
  -
  +      _crossover();
  +      _mutation();
   
         steps--;
       }
  -
     }
   }
   
  
positive.code:    * Makes crossover and updates population.
     */
    _crossover() {
  
    }
  
    GA.start([int chromosomes = 4, int steps = 20]) {
  
negative.code:  * Repeat algorithm until some maximum iterations number.
   */
  class GA {
    List<int> _population = [];
  
    static const xBits = 16;
  
    static const maxX = 1 << xBits;
  
    final random = new Random();
  
    /**
     * Initializes population of [number] chromosomes.
     */
    _initPopulation(int number) {
      for (var i = 0; i < number; i++) {
        _population.add(random.nextInt(maxX));
      }
  