Step 1 - Int

int? tryParseInt(String? raw) {
  if (raw == null) return null;
  final t = raw.trim();
  if (t.isEmpty) return null;
  return int.tryParse(t);
}

Step 2 - Double

double? tryParseDouble(String? raw) {
  if (raw == null) return null;
  final t = raw.trim();
  if (t.isEmpty) return null;
  return double.tryParse(t);
}

Step 3 - Bool (small convention table)

bool? tryParseBool(String? raw) {
  if (raw == null) return null;
  switch (raw.trim().toLowerCase()) {
    case 'true':
    case '1':
    case 'yes':
      return true;
    case 'false':
    case '0':
    case 'no':
      return false;
    default:
      return null;
  }
}

void main() {
  print(tryParseInt(' 42 '));
  print(tryParseDouble('3.14'));
  print(tryParseBool('YES'));
  print(tryParseInt('nope'));
}

Practice tasks

• Add Result<int> parseIntResult(String? raw) using your Result type from earlier guides.
• Reject double strings that are NaN or infinite after parse (return null or Result.err).
• Add List<int>? tryParseIntList(String? csv) splitting on , and failing if any part is invalid.