Module lending_iterator::lending_iterator::adapters

source ·
Expand description

LendingIterator adapters.

Example

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  • use ::lending_iterator::prelude::*;

let mut array = [0; 15];
array[1] = 1;
// Let's hand-roll our iterator lending `&mut` sliding windows:
let mut iter = {
        // initial state:
    ::lending_iterator::repeat_mut((&mut array, 0))
        // main logic (lending _slices_):
        .filter_map::<HKT!(&mut [u16]), _>(|[], (array, start)| {
            let to_yield =
                array
                    .get_mut(*start..)?
                    .get_mut(..3)?
            ;
            *start += 1;
            Some(to_yield)
        })
        // tiny type adaptor (lending _arrays_):
        .map_to_mut(|[], slice| <&mut [u16; 3]>::try_from(slice).unwrap())
    //   ⬑convenience (no need to turbofish an HKT) that is equivalent to:
    //  .map::<HKT!(&mut [u16; 3]), _>(|[], slice| <_>::try_from(slice).unwrap())
};
while let Some(&mut [a, b, ref mut next]) = iter.next() {
    *next = a + b;
}
assert_eq!(
    array,
    [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377],
);

Notice how any adapters that return a lending / dependent type (such as &mut … for .{filter_,}map()) are required to take an extra [] “dummy” parameter for the closure input. This is due to a technical limitation of the language, and having to add [], was the least cumbersome way that I could find to work around it 😔

Structs