Function chumsky::primitive::filter_map

pub fn filter_map<I, O, F: Fn(E::Span, I) -> Result<O, E>, E: Error<I>>(
    f: F
) -> FilterMap<F, E>

A parser that accepts a input and tests it against the given fallible function.

This function allows integration with custom error types to allow for custom parser errors.

Before using this function, consider whether the select macro would serve you better.

The output type of this parser is I, the input that was found.

Examples

let numeral = filter_map(|span, c: char| match c.to_digit(10) {
    Some(x) => Ok(x),
    None => Err(Simple::custom(span, format!("'{}' is not a digit", c))),
});

assert_eq!(numeral.parse("3"), Ok(3));
assert_eq!(numeral.parse("7"), Ok(7));
assert_eq!(numeral.parse("f"), Err(vec![Simple::custom(0..1, "'f' is not a digit")]));