hi, i'm ana —
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use std::time::Duration;

/// Retries a fallible operation with exponential backoff.
/// Keeps the call site honest: no magic, no hidden loops.
pub fn retry<T, E, F>(mut f: F) -> Result<T, E>
where
    F: FnMut() -> Result<T, E>,
{
    let mut delay = Duration::from_millis(100);
    loop {
        match f() {
            Ok(v) => return Ok(v),
            Err(_) => {
                std::thread::sleep(delay);
                delay *= 2;
                if delay > Duration::from_secs(5) { return Err(delay_err()); }
            }
        }
    }
}

fn delay_err() -> ??? { unimplemented!("you handle the error type") }