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Merge pull request #559 from k-nasa/fix_max_by_key

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Fix stream max_by_key and min_by_key
This commit is contained in:
Yoshua Wuyts 2019-11-19 23:43:46 +01:00 committed by GitHub
commit f24b3a4520
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3 changed files with 31 additions and 21 deletions
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21
src/stream/stream/max_by_key.rs
View file

@ -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 +37,29 @@ 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(this.max.take().map(|max| max.1)),
}
}
}

21
src/stream/stream/min_by_key.rs
View file

@ -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 MinByKeyFuture<S, T, K> {
#[pin]
stream: S,
min: Option<T>,
min: Option<(T, T)>,
key_by: K,
}
}
@ -37,24 +37,29 @@ 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.min.take() {
None => *this.min = Some(new),
Some(old) => match new.cmp(&old) {
Ordering::Less => *this.min = Some(new),
match this.min.take() {
None => *this.min = Some((key, value)),
Some(old) => match key.cmp(&old.0) {
Ordering::Less => *this.min = Some((key, value)),
_ => *this.min = Some(old),
},
}
Poll::Pending
}
None => Poll::Ready(this.min.take()),
None => Poll::Ready(this.min.take().map(|min| min.1)),
}
}
}

10
src/stream/stream/mod.rs
View file

@ -875,10 +875,10 @@ extension_trait! {
use async_std::prelude::*;
use async_std::stream;
let s = stream::from_iter(vec![1isize, 2, -3]);
let s = stream::from_iter(vec![-1isize, 2, -3]);
let min = s.clone().min_by_key(|x| x.abs()).await;
assert_eq!(min, Some(1));
assert_eq!(min, Some(-1));
let min = stream::empty::<isize>().min_by_key(|x| x.abs()).await;
assert_eq!(min, None);
@ -911,12 +911,12 @@ extension_trait! {
use async_std::prelude::*;
use async_std::stream;
let s = stream::from_iter(vec![-1isize, -2, -3]);
let s = stream::from_iter(vec![-3_i32, 0, 1, 5, -10]);
let max = s.clone().max_by_key(|x| x.abs()).await;
assert_eq!(max, Some(3));
assert_eq!(max, Some(-10));
let max = stream::empty::<isize>().min_by_key(|x| x.abs()).await;
let max = stream::empty::<isize>().max_by_key(|x| x.abs()).await;
assert_eq!(max, None);
#
# }) }