anchor.diff:    }
     
     get balance => _balance;
  -  set balance(double value) {
  +  set balance(num value) {
       if (value.isNegative) {
         throw new Exception('Balance cannot be negative');
       }
  
positive.code:  */
  class Debt {
    var _label;
    double _balance;
    double _rate;
    double _minPayment;
    
    Debt(String label, double balance, double rate, double minPayment) {
      this.label = label;
      this.balance = balance;
      this.rate = rate;
  
negative.code:   }
    
    get rate => _rate;
    set rate(num value) {
      if (value.isNegative) {
        throw new Exception('Rate cannot be negative');
      }
  