pub fn cond<I, E, F>(
b: bool,
f: F,
) -> impl Parser<I, Output = Option<<F as Parser<I>>::Output>, Error = E>where
E: ParseError<I>,
F: Parser<I, Error = E>,Expand description
Calls the parser if the condition is met.
use nom::combinator::cond;
use nom::character::complete::alpha1;
fn parser(b: bool, i: &str) -> IResult<&str, Option<&str>> {
cond(b, alpha1).parse(i)
}
assert_eq!(parser(true, "abcd;"), Ok((";", Some("abcd"))));
assert_eq!(parser(false, "abcd;"), Ok(("abcd;", None)));
assert_eq!(parser(true, "123;"), Err(Err::Error(Error::new("123;", ErrorKind::Alpha))));
assert_eq!(parser(false, "123;"), Ok(("123;", None)));