Function callbag::scan

pub fn scan<I: 'static, O: 'static, F: 'static, S>(
    reducer: F, 
    seed: O
) -> Box<dyn Fn(S) -> Source<O>> where
    O: Send + Sync + Clone,
    F: Fn(O, I) -> O + Send + Sync + Clone,
    S: Into<Arc<Source<I>>>, 

Callbag operator that combines consecutive values from the same source.

It’s essentially like Iterator::scan, delivering a new accumulated value for each value from the callbag source.

Works on either pullable or listenable sources.

See https://github.com/staltz/callbag-scan/blob/4ade1071e52f53a4b712d38f4e975f52ce8710c8/readme.js#L28-L40

Examples

use crossbeam_queue::SegQueue;
use std::sync::Arc;

use callbag::{for_each, from_iter, scan};

let actual = Arc::new(SegQueue::new());

let iter_source = from_iter([1, 2, 3, 4, 5]);
let scanned = scan(|prev, x| prev + x, 0)(iter_source);

for_each({
    let actual = Arc::clone(&actual);
    move |x| {
        println!("{}", x);
        actual.push(x);
    }
})(scanned);

assert_eq!(
    &{
        let mut v = vec![];
        for _i in 0..actual.len() {
            v.push(actual.pop().unwrap());
        }
        v
    }[..],
    [1, 3, 6, 10, 15]
);