D20 is a Dart library for RPG dice rolling. Supports standard notation (like "2d12", "d6+5" and "2d20-L").

Add the following to your pubspec.yaml file:

dependencies:
  d20: <1.0.0

then run:

pub get

or with flutter:

flutter packages get

import 'package:d20/d20.dart';

void main() {
  final d20 = D20();
  print(d20.roll('2d8+5+5d6'));
}

One can also get (probably) useful information of roll results:

import 'package:d20/d20.dart';

void main() {
  final d20 = D20();
  final stats = d20.rollWithStatistics('2d8+5+5d6');
  print(stats.results[0].faces);
  print(stats.results[1].results);
}

The standard dice notation will be parsed, such as 2d8+4.

When a -L or -H follows a roll, as in 2d20-L, the lowest (or highest) roll of the sequence will be subtracted from the result.

You can also use mathematical operators, such as 1d6*3 or 10d4/d6; or even 10 * sin(d20), though I'm not sure why you'd need that.

You can also use use the d% notation instead of d100.