# Function nom::multi::fold_many_m_n

source · [−]

    pub fn fold_many_m_n<I, O, E, F, G, H, R>(
        min: usize,
        max: usize,
        parse: F,
        init: H,
        fold: G
    ) -> impl FnMut(I) -> IResult<I, R, E> where
        I: Clone + InputLength,
        F: Parser<I, O, E>,
        G: FnMut(R, O) -> R,
        H: FnMut() -> R,
        E: ParseError<I>,

Expand description

Repeats the embedded parser `m..=n` times, calling `g` to gather the results

This stops before `n` when the parser returns `Err::Error`. To instead chain an error up, see `cut`.

## Arguments

- `m` The minimum number of iterations.
- `n` The maximum number of iterations.
- `f` The parser to apply.
- `init` A function returning the initial value.
- `g` The function that combines a result of `f` with the current accumulator.

Note: If the parser passed to `many1` accepts empty inputs (like `alpha0` or `digit0`), `many1` will return an error, to prevent going into an infinite loop.

    use nom::multi::fold_many_m_n;
    use nom::bytes::complete::tag;

    fn parser(s: &str) -> IResult<&str, Vec<&str>> {
      fold_many_m_n(
        0,
        2,
        tag("abc"),
        Vec::new,
        |mut acc: Vec<_>, item| {
          acc.push(item);
          acc
        }
      )(s)
    }

    assert_eq!(parser("abcabc"), Ok(("", vec!["abc", "abc"])));
    assert_eq!(parser("abc123"), Ok(("123", vec!["abc"])));
    assert_eq!(parser("123123"), Ok(("123123", vec![])));
    assert_eq!(parser(""), Ok(("", vec![])));
    assert_eq!(parser("abcabcabc"), Ok(("abc", vec!["abc", "abc"])));