# Function nom::bytes::complete::is_a

source · [−]

    pub fn is_a<T, Input, Error: ParseError<Input>>(
        arr: T
    ) -> impl Fn(Input) -> IResult<Input, Input, Error> where
        Input: InputTakeAtPosition,
        T: FindToken<<Input as InputTakeAtPosition>::Item>,

Expand description

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.

It will return a `Err(Err::Error((_, ErrorKind::IsA)))` if the pattern wasn’t met.

## Example

    use nom::bytes::complete::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"), Ok(("", "D15EA5E")));
    assert_eq!(hex(""), Err(Err::Error(Error::new("", ErrorKind::IsA))));