iterator.rs - mozsearch

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use std::collections::HashMap;

use std::iter::Iterator;

use winnow::ascii::alphanumeric1;

use winnow::combinator::iterator;

use winnow::combinator::{separated_pair, terminated};

use winnow::prelude::*;

fn main() {

    let mut data = "abcabcabcabc";

    fn parser<'s>(i: &mut &'s str) -> ModalResult<&'s str> {

        "abc".parse_next(i)

    // `from_fn` (available from Rust 1.34) can create an iterator

    // from a closure

    let it = std::iter::from_fn(move || parser.parse_next(&mut data).ok());

    for value in it {

        println!("parser returned: {value}");

    println!("\n********************\n");

    let mut data = "abcabcabcabc";

    // if `from_fn` is not available, it is possible to fold

    // over an iterator of functions

    let res = std::iter::repeat(parser)

        .take(3)

        .try_fold(Vec::new(), |mut acc, mut parser| {

            parser.parse_next(&mut data).map(|o| {

                acc.push(o);

acc

})

});

    // will print "parser iterator returned: Ok(("abc", ["abc", "abc", "abc"]))"

    println!("\nparser iterator returned: {res:?}");

    println!("\n********************\n");

    let data = "key1:value1,key2:value2,key3:value3,;";

    // `winnow::combinator::iterator` will return an iterator

    // producing the parsed values. Compared to the previous

    // solutions:

    // - we can work with a normal iterator like `from_fn`

    // - we can get the remaining input afterwards, like with the `try_fold` trick

    let mut winnow_it = iterator(

        data,

        terminated(separated_pair(alphanumeric1, ":", alphanumeric1), ","),

);

    let res = winnow_it

        .map(|(k, v)| (k.to_uppercase(), v))

        .collect::<HashMap<_, _>>();

    let parser_result: ModalResult<(_, _), ()> = winnow_it.finish();

    let (remaining_input, ()) = parser_result.unwrap();

    // will print "iterator returned {"key1": "value1", "key3": "value3", "key2": "value2"}, remaining input is ';'"

    println!("iterator returned {res:?}, remaining input is '{remaining_input}'");