anchor.diff:   */
   library fraction;
   
  +import 'package:meta/meta.dart';
   import 'int_math.dart' as int_math;
   
   /**
  
positive.code: 
    int toInt() => numerator ~/ denominator;
  
    String toString() => '$numerator/$denominator';
  
  }
negative.code:     return new Fraction._(-numerator, denominator);
    }
  
    @override
    bool operator == (other) {
      return other is Fraction
          && numerator == other.numerator
          && denominator == other.denominator;
    }
  
    @override
    int get hashCode {
      return numerator.hashCode + denominator.hashCode;
    }
  
    @override
    int compareTo(Fraction other) {
      return (numerator * other.denominator)
          .compareTo(other.numerator * denominator);
  