parse method

Implementation

@override
Result<List<O>>? parse(State<I> state) {
  final pos = state.pos;
  final r1 = p1.parse(state);
  if (r1 != null) {
    final r2 = p2.parse(state);
    if (r2 != null) {
      final r3 = p3.parse(state);
      if (r3 != null) {
        final r4 = p4.parse(state);
        if (r4 != null) {
          return Result([r1.value, r2.value, r3.value, r4.value]);
        }
      }
    }
  }

  state.pos = pos;
  return null;
}