code: function(s) {
                                          var result = new Symbol(1);
                                          s.each(function(x) {
                                              result = _.multiply(result, x.fname === 'abs' ? x.args[0] : x);
                                          });
                                          return result;
                                      }
docs: //then we have atan abs is redundants since the sign appears in both denom and num.