pub fn opt<I: Clone, O, E: ParseError<I>, F>(
f: F,
) -> impl FnMut(I) -> IResult<I, Option<O>, E>where
F: Parser<I, O, E>,Expand description
Optional parser, will return None on Err::Error.
To chain an error up, see cut.
use nom::combinator::opt;
use nom::character::complete::alpha1;
fn parser(i: &str) -> IResult<&str, Option<&str>> {
opt(alpha1)(i)
}
assert_eq!(parser("abcd;"), Ok((";", Some("abcd"))));
assert_eq!(parser("123;"), Ok(("123;", None)));