parse method

@override Tuple1<Tuple4<E1, E2, E3, E4>>? parse(ParseState state)

Parses input data actively and produces the result.

Returns Tuple1 of the result if parsing was successful; otherwise returns null.

final r1 = p.parse(state);

Implementation

@override
Tuple1<Tuple4<E1, E2, E3, E4>>? parse(ParseState 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) {
          final v1 = Tuple4(r1.$0, r2.$0, r3.$0, r4.$0);
          return Tuple1(v1);
        }
      }
    }
  }

  state.pos = pos;
}