Function cond_else

pub fn cond_else<I, O, E: ParseError<I>, C, F, G>(
    cond: C,
    first: F,
    second: G,
) -> impl FnMut(I) -> IResult<I, O, E>
where
    C: Fn() -> bool,
    F: Parser<I, O, E>,
    G: Parser<I, O, E>,

Helper macro for nom parsers: run first parser if condition is true, else second parser