Function nom::combinator::verify
source · [−]pub fn verify<I: Clone, O1, O2, E: ParseError<I>, F, G>(
first: F,
second: G
) -> impl FnMut(I) -> IResult<I, O1, E> where
F: Parser<I, O1, E>,
G: Fn(&O2) -> bool,
O1: Borrow<O2>,
O2: ?Sized,
Expand description
Returns the result of the child parser if it satisfies a verification function.
The verification function takes as argument a reference to the output of the parser.
use nom::combinator::verify;
use nom::character::complete::alpha1;
let mut parser = verify(alpha1, |s: &str| s.len() == 4);
assert_eq!(parser("abcd"), Ok(("", "abcd")));
assert_eq!(parser("abcde"), Err(Err::Error(("abcde", ErrorKind::Verify))));
assert_eq!(parser("123abcd;"),Err(Err::Error(("123abcd;", ErrorKind::Alpha))));