Do you have callbacks (and other difficult for iterators) and are you tired of .collect() them into Vecs? There is a solution.

Buter - buffered iterator with fluid buffer, which is used as a place for all iterations

Usage

```rust fn callbackwork(mut f: F) where F: FnMut(usize), { for i in 0..10000 { f(i); } }

use buter::Buter;

struct Worker { buf: Buter, // ... }

impl Worker { fn workimpl(&self) -> impl Iterator + ' { let mut writer = self.buf.writer(); callbackwork(|i| writer.extend(Some(i))); writer.intoiter() } } ```

Benches

This is appropriate both with large results and with small ones rust // test buter ... bench: 14 ns/iter (+/- 5) // test vec_push ... bench: 212 ns/iter (+/- 130) // test vec_push_with_capacity ... bench: 54 ns/iter (+/- 32) rust // buter time: [2.7939 ms 2.8248 ms 2.8551 ms] // vec_push time: [7.2415 ms 7.3449 ms 7.4483 ms] // vec_push_with_capacity time: [4.3433 ms 4.3965 ms 4.4500 ms]