1. class Duration implements Comparable<Duration> {
    2.   static const int microsecondsPerMillisecond = 1000;
    3.   static const int millisecondsPerSecond = 1000;
    4.   static const int secondsPerMinute = 60;
    5.   static const int minutesPerHour = 60;
    6.   static const int hoursPerDay = 24;
    8.   static const int microsecondsPerSecond =
    9.       microsecondsPerMillisecond * millisecondsPerSecond;
    10.   static const int microsecondsPerMinute =
    11.       microsecondsPerSecond * secondsPerMinute;
    12.   static const int microsecondsPerHour = microsecondsPerMinute * minutesPerHour;
    13.   static const int microsecondsPerDay = microsecondsPerHour * hoursPerDay;
    14.   static const int millisecondsPerMinute =
    15.       millisecondsPerSecond * secondsPerMinute;
    16.   static const int millisecondsPerHour = millisecondsPerMinute * minutesPerHour;
    17.   static const int millisecondsPerDay = millisecondsPerHour * hoursPerDay;
    18.   static const int secondsPerHour = secondsPerMinute * minutesPerHour;
    19.   static const int secondsPerDay = secondsPerHour * hoursPerDay;
    20.   static const int minutesPerDay = minutesPerHour * hoursPerDay;
    22.   static const Duration zero = Duration(seconds: 0);
    23.   final int _duration;
    24.   const Duration(
    25.       {int days = 0,
    26.       int hours = 0,
    27.       int minutes = 0,
    28.       int seconds = 0,
    29.       int milliseconds = 0,
    30.       int microseconds = 0})
    31.       : this._microseconds(microsecondsPerDay * days +
    32.             microsecondsPerHour * hours +
    33.             microsecondsPerMinute * minutes +
    34.             microsecondsPerSecond * seconds +
    35.             microsecondsPerMillisecond * milliseconds +
    36.             microseconds);
    38.   const Duration._microseconds(this._duration);
    40.   Duration operator +(Duration other) {
    41.     return Duration._microseconds(_duration + other._duration);
    42.   }
    44.   Duration operator -(Duration other) {
    45.     return Duration._microseconds(_duration - other._duration);
    46.   }
    48.   Duration operator *(num factor) {
    49.     return Duration._microseconds((_duration * factor).round());
    50.   }
    52.   Duration operator ~/(int quotient) {
    53.     if (quotient == 0) throw IntegerDivisionByZeroException();
    54.     return Duration._microseconds(_duration ~/ quotient);
    55.   }
    57.   bool operator <(Duration other) => this._duration < other._duration;
    59.   bool operator >(Duration other) => this._duration > other._duration;
    61.   bool operator <=(Duration other) => this._duration <= other._duration;
    63.   bool operator >=(Duration other) => this._duration >= other._duration;
    65.   int get inDays => _duration ~/ Duration.microsecondsPerDay;
    67.   int get inHours => _duration ~/ Duration.microsecondsPerHour;
    69.   int get inMinutes => _duration ~/ Duration.microsecondsPerMinute;
    71.   int get inSeconds => _duration ~/ Duration.microsecondsPerSecond;
    73.   int get inMilliseconds => _duration ~/ Duration.microsecondsPerMillisecond;
    75.   int get inMicroseconds => _duration;
    77.   bool operator ==(Object other) =>
    78.       other is Duration && _duration == other.inMicroseconds;
    80.   int get hashCode => _duration.hashCode;
    82.   int compareTo(Duration other) => _duration.compareTo(other._duration);
    84.   String toString() {
    85.     String sixDigits(int n) {
    86.       if (n >= 100000) return "$n";
    87.       if (n >= 10000) return "0$n";
    88.       if (n >= 1000) return "00$n";
    89.       if (n >= 100) return "000$n";
    90.       if (n >= 10) return "0000$n";
    91.       return "00000$n";
    92.     }
    93.     String twoDigits(int n) {
    94.       if (n >= 10) return "$n";
    95.       return "0$n";
    96.     }
    98.     if (inMicroseconds < 0) { return "-${-this}"; }
    99.     String twoDigitMinutes =
    100.         twoDigits(inMinutes.remainder(minutesPerHour) as int);
    101.     String twoDigitSeconds =
    102.         twoDigits(inSeconds.remainder(secondsPerMinute) as int);
    103.     String sixDigitUs =
    104.         sixDigits(inMicroseconds.remainder(microsecondsPerSecond) as int);
    105.     return "$inHours:$twoDigitMinutes:$twoDigitSeconds.$sixDigitUs";
    106.   }
    108.   bool get isNegative => _duration < 0;
    110.   Duration abs() => Duration._microseconds(_duration.abs());
    112.   Duration operator -() => Duration._microseconds(0 - _duration);
    113. }
    116. main(List<String> args) {
    117.   print(Duration(milliseconds:  -1));
    118. }
    2. @immutable
    3. class Permission {
    4.   const Permission._(this.value);
    5.   factory Permission.byValue(int value) => values[value];
    7.   final int value;
    8.   static const calendar = Permission._(0);
    9.   static const camera = Permission._(1);
    10.   static const contacts = Permission._(2);
    11.   static const location = PermissionWithService._(3);
    12.   static const locationAlways = PermissionWithService._(4);
    13.   static const locationWhenInUse = PermissionWithService._(5);
    14.   static const mediaLibrary = Permission._(6);
    15.   static const microphone = Permission._(7);
    16.   static const phone = PermissionWithService._(8);
    17.   static const photos = Permission._(9);
    18.   static const photosAddOnly = Permission._(10);
    19.   static const reminders = Permission._(11);
    20.   static const sensors = Permission._(12);
    21.   static const sms = Permission._(13);
    22.   static const speech = Permission._(14);
    23.   static const storage = Permission._(15);
    24.   static const ignoreBatteryOptimizations = Permission._(16);
    25.   static const notification = Permission._(17);
    26.   static const accessMediaLocation = Permission._(18);
    27.   static const activityRecognition = Permission._(19);
    28.   static const unknown = Permission._(20);
    29.   static const bluetooth = Permission._(21);
    30.   static const manageExternalStorage = Permission._(22);
    31.   static const systemAlertWindow = Permission._(23);
    32.   static const requestInstallPackages = Permission._(24);
    33.   static const appTrackingTransparency = Permission._(25);
    34.   static const criticalAlerts = Permission._(26);
    35.   static const accessNotificationPolicy = Permission._(27);
    36.   static const bluetoothScan = Permission._(28);
    37.   static const bluetoothAdvertise = Permission._(29);
    38.   static const bluetoothConnect = Permission._(30);
    40.   static const List<Permission> values = <Permission>[
    41.     calendar,
    42.     camera,
    43.     contacts,
    44.     location,
    45.     locationAlways,
    46.     locationWhenInUse,
    47.     mediaLibrary,
    48.     microphone,
    49.     phone,
    50.     photos,
    51.     photosAddOnly,
    52.     reminders,
    53.     sensors,
    54.     sms,
    55.     speech,
    56.     storage,
    57.     ignoreBatteryOptimizations,
    58.     notification,
    59.     accessMediaLocation,
    60.     activityRecognition,
    61.     unknown,
    62.     bluetooth,
    63.     manageExternalStorage,
    64.     systemAlertWindow,
    65.     requestInstallPackages,
    66.     appTrackingTransparency,
    67.     criticalAlerts,
    68.     accessNotificationPolicy,
    69.     bluetoothScan,
    70.     bluetoothAdvertise,
    71.     bluetoothConnect,
    72.   ];
    74.   static const List<String> _names = <String>[
    75.     'calendar',
    76.     'camera',
    77.     'contacts',
    78.     'location',
    79.     'locationAlways',
    80.     'locationWhenInUse',
    81.     'mediaLibrary',
    82.     'microphone',
    83.     'phone',
    84.     'photos',
    85.     'photosAddOnly',
    86.     'reminders',
    87.     'sensors',
    88.     'sms',
    89.     'speech',
    90.     'storage',
    91.     'ignoreBatteryOptimizations',
    92.     'notification',
    93.     'access_media_location',
    94.     'activity_recognition',
    95.     'unknown',
    96.     'bluetooth',
    97.     'manageExternalStorage',
    98.     'systemAlertWindow',
    99.     'requestInstallPackages',
    100.     'appTrackingTransparency',
    101.     'criticalAlerts',
    102.     'accessNotificationPolicy',
    103.     'bluetoothScan',
    104.     'bluetoothAdvertise',
    105.     'bluetoothConnect',
    106.   ];
    108.   @override
    109.   String toString() => 'Permission.${_names[value]}';
    111.   @override
    112.   bool operator ==(Object other) {
    113.     if (identical(this, other)) {
    114.       return true;
    115.     }
    116.     if (other.runtimeType != runtimeType) {
    117.       return false;
    118.     }
    119.     return other is Permission && other.value == value;
    120.   }
    122.   @override
    123.   int get hashCode => value.hashCode;
    124. }