Adds partial_cmp.rs file and partial_cmp signature to mod.rs

src/stream/stream/mod.rs

@@ -30,19 +30,17 @@ mod filter_map;
 mod find;
 mod find_map;
 mod fold;
-mod for_each;
 mod fuse;
 mod inspect;
-mod map;
 mod min_by;
 mod next;
 mod nth;
+mod partial_cmp;
 mod scan;
 mod skip;
 mod skip_while;
 mod step_by;
 mod take;
-mod try_for_each;
 mod zip;
 
 use all::AllFuture;
@@ -52,17 +50,15 @@ use filter_map::FilterMap;
 use find::FindFuture;
 use find_map::FindMapFuture;
 use fold::FoldFuture;
-use for_each::ForEachFuture;
 use min_by::MinByFuture;
 use next::NextFuture;
 use nth::NthFuture;
-use try_for_each::TryForEeachFuture;
+use partial_cmp::PartialCmpFuture;
 
 pub use chain::Chain;
 pub use filter::Filter;
 pub use fuse::Fuse;
 pub use inspect::Inspect;
-pub use map::Map;
 pub use scan::Scan;
 pub use skip::Skip;
 pub use skip_while::SkipWhile;
@@ -344,37 +340,6 @@ extension_trait! {
             Enumerate::new(self)
         }
 
-        #[doc = r#"
-            Takes a closure and creates a stream that calls that closure on every element of this stream.
-
-            # Examples
-
-            ```
-            # fn main() { async_std::task::block_on(async {
-            #
-            use async_std::prelude::*;
-            use std::collections::VecDeque;
-
-            let s: VecDeque<_> = vec![1, 2, 3].into_iter().collect();
-            let mut s = s.map(|x| 2 * x);
-
-            assert_eq!(s.next().await, Some(2));
-            assert_eq!(s.next().await, Some(4));
-            assert_eq!(s.next().await, Some(6));
-            assert_eq!(s.next().await, None);
-
-            #
-            # }) }
-            ```
-        "#]
-        fn map<B, F>(self, f: F) -> Map<Self, F, Self::Item, B>
-        where
-            Self: Sized,
-            F: FnMut(Self::Item) -> B,
-        {
-            Map::new(self, f)
-        }
-
         #[doc = r#"
             A combinator that does something with each element in the stream, passing the value
             on.
@@ -791,41 +756,6 @@ extension_trait! {
             FoldFuture::new(self, init, f)
         }
 
-        #[doc = r#"
-            Call a closure on each element of the stream.
-
-            # Examples
-
-            ```
-            # fn main() { async_std::task::block_on(async {
-            #
-            use async_std::prelude::*;
-            use std::collections::VecDeque;
-            use std::sync::mpsc::channel;
-
-            let (tx, rx) = channel();
-
-            let s: VecDeque<usize> = vec![1, 2, 3].into_iter().collect();
-            let sum = s.for_each(move |x| tx.clone().send(x).unwrap()).await;
-
-            let v: Vec<_> = rx.iter().collect();
-
-            assert_eq!(v, vec![1, 2, 3]);
-            #
-            # }) }
-            ```
-        "#]
-        fn for_each<F>(
-            self,
-            f: F,
-        ) -> impl Future<Output = ()> [ForEachFuture<Self, F, Self::Item>]
-        where
-            Self: Sized,
-            F: FnMut(Self::Item),
-        {
-            ForEachFuture::new(self, f)
-        }
-
         #[doc = r#"
             Tests if any element of the stream matches a predicate.
 
@@ -997,51 +927,6 @@ extension_trait! {
             Skip::new(self, n)
         }
 
-        #[doc = r#"
-            Applies a falliable function to each element in a stream, stopping at first error and returning it.
-
-            # Examples
-
-            ```
-            # fn main() { async_std::task::block_on(async {
-            #
-            use std::collections::VecDeque;
-            use std::sync::mpsc::channel;
-            use async_std::prelude::*;
-
-            let (tx, rx) = channel();
-
-            let s: VecDeque<usize> = vec![1, 2, 3].into_iter().collect();
-            let s = s.try_for_each(|v| {
-                if v % 2 == 1 {
-                    tx.clone().send(v).unwrap();
-                    Ok(())
-                } else {
-                    Err("even")
-                }
-            });
-
-            let res = s.await;
-            drop(tx);
-            let values: Vec<_> = rx.iter().collect();
-
-            assert_eq!(values, vec![1]);
-            assert_eq!(res, Err("even"));
-            #
-            # }) }
-            ```
-        "#]
-        fn try_for_each<F, E>(
-            self,
-            f: F,
-        ) -> impl Future<Output = E> [TryForEeachFuture<Self, F, Self::Item, E>]
-        where
-            Self: Sized,
-            F: FnMut(Self::Item) -> Result<(), E>,
-        {
-            TryForEeachFuture::new(self, f)
-        }
-
         #[doc = r#"
             'Zips up' two streams into a single stream of pairs.
 
@@ -1187,6 +1072,46 @@ extension_trait! {
         {
             Merge::new(self, other)
         }
+
+        #[doc = r#"
+            Lexicographically compares the elements of this `Stream` with those
+            of another.
+
+            # Examples
+            ```
+            # fn main() { async_std::task::block_on(async {
+            #
+            use async_std::prelude::*;
+            use std::collections::VecDeque;
+
+            use std::cmp::Ordering;
+
+            let s1 = VecDeque::from(vec![1]);
+            let s2 = VecDeque::from(vec![1, 2]);
+            let s3 = VecDeque::from(vec![1, 2, 3]);
+            let s4 = VecDeque::from(vec![1, 2, 4]);
+
+            assert_eq!(s1.clone().partial_cmp(s1.clone()).await, Some(Ordering::Equal));
+            assert_eq!(s1.clone().partial_cmp(s2.clone()).await, Some(Ordering::Less));
+            assert_eq!(s2.clone().partial_cmp(s1.clone()).await, Some(Ordering::Greater));       
+            assert_eq!(s3.clone().partial_cmp(s4.clone()).await, Some(Ordering::Less));
+            assert_eq!(s4.clone().partial_cmp(s3.clone()).await, Some(Ordering::Greater));                             
+
+            #
+            # }) }
+            ```
+        "#]
+        fn partial_cmp<S>(
+           self,
+           other: S
+        ) -> impl Future<Output = Option<Ordering>>  [PartialCmpFuture<Self, S>]
+        where
+            Self: Sized + Stream,
+            S: Stream,
+            <Self as Stream>::Item: PartialOrd<S::Item>,
+        {
+            PartialCmpFuture::new(self, other)
+        }        
     }
 
     impl<S: Stream + Unpin + ?Sized> Stream for Box<S> {

src/stream/stream/partial_cmp.rs

@@ -0,0 +1,92 @@
+use std::cmp::Ordering;
+use std::pin::Pin;
+
+use super::fuse::Fuse;
+use crate::future::Future;
+use crate::prelude::*;
+use crate::stream::Stream;
+use crate::task::{Context, Poll};
+
+// Lexicographically compares the elements of this `Stream` with those
+// of another.
+#[doc(hidden)]
+#[allow(missing_debug_implementations)]
+pub struct PartialCmpFuture<L: Stream, R: Stream> {
+    l: Fuse<L>,
+    r: Fuse<R>,
+    l_cache: Option<L::Item>,
+    r_cache: Option<R::Item>,
+}
+
+impl<L: Stream, R: Stream> PartialCmpFuture<L, R> {
+    pin_utils::unsafe_pinned!(l: Fuse<L>);
+    pin_utils::unsafe_pinned!(r: Fuse<R>);
+    pin_utils::unsafe_unpinned!(l_cache: Option<L::Item>);
+    pin_utils::unsafe_unpinned!(r_cache: Option<R::Item>);
+
+    pub(super) fn new(l: L, r: R) -> Self {
+        PartialCmpFuture {
+            l: l.fuse(),
+            r: r.fuse(),
+            l_cache: None,
+            r_cache: None,
+        }
+    }
+}
+
+impl<L: Stream, R: Stream> Future for PartialCmpFuture<L, R>
+where
+    L: Stream + Sized,
+    R: Stream + Sized,
+    L::Item: PartialOrd<R::Item>,
+{
+    type Output = Option<Ordering>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        loop {
+            // Short circuit logic
+            // Stream that completes earliest can be considered Less, etc
+            let l_complete = self.l.done && self.as_mut().l_cache.is_none();
+            let r_complete = self.r.done && self.as_mut().r_cache.is_none();
+
+            if l_complete && r_complete {
+                return Poll::Ready(Some(Ordering::Equal));
+            } else if l_complete {
+                return Poll::Ready(Some(Ordering::Less));
+            } else if r_complete {
+                return Poll::Ready(Some(Ordering::Greater));
+            }
+
+            // Get next value if possible and necesary
+            if !self.l.done && self.as_mut().l_cache.is_none() {
+                let l_next = futures_core::ready!(self.as_mut().l().poll_next(cx));
+                if let Some(item) = l_next {
+                    *self.as_mut().l_cache() = Some(item);
+                }
+            }
+
+            if !self.r.done && self.as_mut().r_cache.is_none() {
+                let r_next = futures_core::ready!(self.as_mut().r().poll_next(cx));
+                if let Some(item) = r_next {
+                    *self.as_mut().r_cache() = Some(item);
+                }
+            }
+
+            // Compare if both values are available.
+            if self.as_mut().l_cache.is_some() && self.as_mut().r_cache.is_some() {
+                let l_value = self.as_mut().l_cache().take().unwrap();
+                let r_value = self.as_mut().r_cache().take().unwrap();
+                let result = l_value.partial_cmp(&r_value);
+
+                if let Some(Ordering::Equal) = result {
+                    // Reset cache to prepare for next comparison
+                    *self.as_mut().l_cache() = None;
+                    *self.as_mut().r_cache() = None;
+                } else {
+                    // Return non equal value
+                    return Poll::Ready(result);
+                }
+            }
+        }
+    }
+}