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)
where I: Clone + InputLength, F: Parser<I, O, E>, G: FnMut(R, O) -> R, H: FnMut() -> R, E: ParseError<I>,
Available on crate feature mtls only.
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"])));