docs: function(numbers)
    {
      var resolver = createNumberResolver( numbers );
      var result = 0;
      var total = 0;
  
      function process(x)
      {
        result += x;
        total++;
      }
  
      function getResult()
      {
        return total === 0 ? 0 : result / total;
      }
  
      return this.aggregate( resolver, isNumber, process, getResult );
    }