Solved mafinar sir's quiz

quiz1.dart

/*
 * String formatter lib by Ahsan Islam
 * https://www.facebook.com/ahsan.islam.505523
*/

class IntegerToDate {
  int number;

  String period;

  IntegerToDate(int number, String period) {
    this.number = number;
    this.period = period;
  }

  DateTime later() {
    var now = DateTime.now();
    return now.add(getDuration(number));
  }

  DateTime ago() {
    var now = DateTime.now();
    return now.add(getDuration(-number));
  }

  getDuration(int value) {
    if (period == 'days') {
      return new Duration(days: value);
    }

    if (period == 'weeks') {
      value *= 7;
      return new Duration(days: value);
    }

    if (period == 'months') {
      value *= 30;
      return new Duration(days: value);
    }

    if (period == 'years') {
      value *= 365;
      return new Duration(days: value);
    }
  }
}

extension NumberToDate on int {
  IntegerToDate days() {
    return new IntegerToDate(this, 'days');
  }

  IntegerToDate weeks() {
    return new IntegerToDate(this, 'weeks');
  }

  IntegerToDate months() {
    return new IntegerToDate(this, 'months');
  }

  IntegerToDate years() {
    return new IntegerToDate(this, 'years');
  }
}

/*
 * Array parser lib by Adib Mohsin
 * https://www.facebook.com/adib.mohsin.39
*/

class MainParser {
  List<int> numbers;

  MainParser(List<int> total) : numbers = total;

  List<int> by(int differ) {
    int curr;
    List<int> total = [];
    for (var i = 0; i < numbers.length; i += differ) {
      curr = numbers[i];
      total.add(curr);
    }
    return total;
  }
}

extension MafinarParser on int {
  MainParser to([int number]) {
    if (number < this) {
      throw new Exception("Number must be greater than this");
    } else {
      List<int> total = [];
      int curr = this;
      int diff = number - this;
      for (var i = -1; i < diff; i++) {
        total.add(curr++);
      }
      return MainParser(total);
    }
  }
}

main() {
  print(10.years().ago());
  print(7.to(11).by(2));
}