ARB parser

parser_definition.dart

void main() {
  final input = stdin.readLineSync();
  final result = PatternDefinition().build().parse(input ?? '');
  if (result is Success) {
    print('Pattern found, result: ${result.value}');
  } else {
    print('Pattern not found');
  }
}
class PatternDefinition extends GrammarDefinition<int?> {
  @override
  Parser<int?> start() => ref0(value).end(); // 1
  Parser<int?> value() => seq3( // 2
        char('{').trim(), // 2a
        digit().plus().flatten(), // 2b
        char('}').trim(), // 2c
      ).map3((_, digits, __) => int.tryParse(digits)); // 3
}