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fix max_by_key mistake

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This commit is contained in:
k-nasa 2019-11-20 00:17:29 +09:00
parent 314a75da28
commit 64b2e10b93
1 changed files with 16 additions and 8 deletions
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24
src/stream/stream/max_by_key.rs
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@ -1,6 +1,6 @@
use std::cmp::Ordering;
use std::pin::Pin;
use std::future::Future;
use std::pin::Pin;
use pin_project_lite::pin_project;
@ -13,7 +13,7 @@ pin_project! {
pub struct MaxByKeyFuture<S, T, K> {
#[pin]
stream: S,
max: Option<T>,
max: Option<(T, T)>,
key_by: K,
}
}
@ -37,24 +37,32 @@ where
type Output = Option<S::Item>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
fn key<B, T>(mut f: impl FnMut(&T) -> B) -> impl FnMut(T) -> (B, T) {
move |x| (f(&x), x)
}
let this = self.project();
let next = futures_core::ready!(this.stream.poll_next(cx));
match next {
Some(new) => {
let new = (this.key_by)(&new);
let (key, value) = key(this.key_by)(new);
cx.waker().wake_by_ref();
match this.max.take() {
None => *this.max = Some(new),
Some(old) => match new.cmp(&old) {
Ordering::Greater => *this.max = Some(new),
match this.max.take() {
None => *this.max = Some((key, value)),
Some(old) => match key.cmp(&old.0) {
Ordering::Greater => *this.max = Some((key, value)),
_ => *this.max = Some(old),
},
}
Poll::Pending
}
None => Poll::Ready(this.max.take()),
None => Poll::Ready(match this.max.take() {
None => None,
Some(max) => Some(max.1),
}),
}
}
}