# Function nom::combinator::consumed

source · [−]

    pub fn consumed<I, O, F, E>(parser: F) -> impl FnMut(I) -> IResult<I, (I, O), E> where
        I: Clone + Offset + Slice<RangeTo<usize>>,
        E: ParseError<I>,
        F: Parser<I, O, E>,

Expand description

if the child parser was successful, return the consumed input with the output as a tuple. Functions similarly to recognize except it returns the parser output as well.

This can be useful especially in cases where the output is not the same type as the input, or the input is a user defined type.

Returned tuple is of the format `(consumed input, produced output)`.

    use nom::combinator::{consumed, value, recognize, map};
    use nom::character::complete::{char, alpha1};
    use nom::bytes::complete::tag;
    use nom::sequence::separated_pair;

    fn inner_parser(input: &str) -> IResult<&str, bool> {
        value(true, tag("1234"))(input)
    }

    let mut consumed_parser = consumed(value(true, separated_pair(alpha1, char(','), alpha1)));

    assert_eq!(consumed_parser("abcd,efgh1"), Ok(("1", ("abcd,efgh", true))));
    assert_eq!(consumed_parser("abcd;"),Err(Err::Error((";", ErrorKind::Char))));

    // the first output (representing the consumed input)
    // should be the same as that of the `recognize` parser.
    let mut recognize_parser = recognize(inner_parser);
    let mut consumed_parser = map(consumed(inner_parser), |(consumed, output)| consumed);

    assert_eq!(recognize_parser("1234"), consumed_parser("1234"));
    assert_eq!(recognize_parser("abcd"), consumed_parser("abcd"));