anchor.diff:      if (this == double.infinity) return "Infinity";
       if (this == -double.infinity) return "-Infinity";
   
  -    return _toStringAsExponential(fractionDigits);
  +    String result = _toStringAsExponential(fractionDigits);
  +    if (this == 0 && isNegative) return '-$result';
  +    return result;
     }
   
     String _toStringAsExponential(int? fractionDigits) {
  
positive.code:       return x.toString();
      }
  
      return _toStringAsFixed(fractionDigits);
    }
  
    String _toStringAsFixed(int fractionDigits) =>
  
negative.code: 
      // Step 4.
      if (isNaN) return "NaN";
      if (this == double.infinity) return "Infinity";
      if (this == -double.infinity) return "-Infinity";
  
      // Step 5 and 6 skipped. Will be dealt with by native function.
  
  