nom_parse_signed.rs

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum Sign {
	Positive,
	Negative,
}

/// Partially parse a signed integer. Return the sign (if present) and
/// the unsigned integer part
fn parse_signed<E>(input: &str) -> IResult<&str, (Option<Sign>, u64), E> {
	pair(
		opt(alt((
			value(Sign::Positive, char('+')),
			value(Sign::Negative, char('-')),
		))),
		map_res(digit1, u64::from_str),
	)(input)
}