code: function range(a, b) {
      var total = b - a;
      var rec = function(x, y) {
          if (y - a >= total) return x;
  
          x[y] = y++;
          return rec(x, y);
      };
      return rec([], a);
  }
docs: ## range(a, b)  Create an array with a given range (length).