Function `is_a`

fn is_a<T, I, Error: ParseError<I>>(arr: T) -> impl FnMut(I) -> crate::internal::IResult<I, I, Error>
where
    I: Input,
    T: FindToken<<I as Input>::Item>

Returns the longest slice of the matches the pattern.

The parser will return the longest slice consisting of the characters in provided in the combinator's argument.

Streaming specific

Streaming version will return a Err::Incomplete(Needed::new(1)) if the pattern wasn't met or if the pattern reaches the end of the input.

Example

# use nom::{Err, error::ErrorKind, Needed, IResult};
use nom::bytes::streaming::is_a;

fn hex(s: &str) -> IResult<&str, &str> {
  is_a("1234567890ABCDEF")(s)
}

assert_eq!(hex("123 and voila"), Ok((" and voila", "123")));
assert_eq!(hex("DEADBEEF and others"), Ok((" and others", "DEADBEEF")));
assert_eq!(hex("BADBABEsomething"), Ok(("something", "BADBABE")));
assert_eq!(hex("D15EA5E"), Err(Err::Incomplete(Needed::new(1))));
assert_eq!(hex(""), Err(Err::Incomplete(Needed::new(1))));