Function fold_repeat0_

fn fold_repeat0_<I, O, E, F, G, H, R>(
    f: &mut F,
    init: &mut H,
    g: &mut G,
    input: &mut I,
) -> PResult<R, E>
where
    I: Stream,
    F: Parser<I, O, E>,
    G: FnMut(R, O) -> R,
    H: FnMut() -> R,
    E: ParserError<I>,