Struct async_std::stream::Scan

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pub struct Scan<S, St, F> { /* private fields */ }
Expand description

A stream to maintain state while polling another stream.

This struct is created by the scan method on Stream. See its documentation for more.

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impl<S: Debug, St: Debug, F: Debug> Debug for Scan<S, St, F>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<S, St, F, B> Stream for Scan<S, St, F>
where S: Stream, F: FnMut(&mut St, S::Item) -> Option<B>,

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type Item = B

Values yielded by the stream.
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fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<B>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted. Read more
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fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream. Read more
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impl<'__pin, S, St, F> Unpin for Scan<S, St, F>
where __Origin<'__pin, S, St, F>: Unpin,

Auto Trait Implementations§

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impl<S, St, F> RefUnwindSafe for Scan<S, St, F>
where F: RefUnwindSafe, S: RefUnwindSafe, St: RefUnwindSafe,

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impl<S, St, F> Send for Scan<S, St, F>
where F: Send, S: Send, St: Send,

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impl<S, St, F> Sync for Scan<S, St, F>
where F: Sync, S: Sync, St: Sync,

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impl<S, St, F> UnwindSafe for Scan<S, St, F>
where F: UnwindSafe, S: UnwindSafe, St: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<I> IntoStream for I
where I: Stream,

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type Item = <I as Stream>::Item

The type of the elements being iterated over.
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type IntoStream = I

Which kind of stream are we turning this into?
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fn into_stream(self) -> I

Creates a stream from a value.
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impl<S> StreamExt for S
where S: Stream + ?Sized,

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fn poll_next(&mut self, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>
where Self: Unpin,

A convenience for calling Stream::poll_next() on !Unpin types.
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fn next(&mut self) -> NextFuture<'_, Self> ⓘ
where Self: Unpin,

Retrieves the next item in the stream. Read more
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fn try_next<T, E>(&mut self) -> TryNextFuture<'_, Self> ⓘ
where Self: Stream<Item = Result<T, E>> + Unpin,

Retrieves the next item in the stream. Read more
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fn count(self) -> CountFuture<Self> ⓘ
where Self: Sized,

Counts the number of items in the stream. Read more
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fn map<T, F>(self, f: F) -> Map<Self, F>
where Self: Sized, F: FnMut(Self::Item) -> T,

Maps items of the stream to new values using a closure. Read more
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fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
where Self: Sized, U: Stream, F: FnMut(Self::Item) -> U,

Maps items to streams and then concatenates them. Read more
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fn flatten(self) -> Flatten<Self>
where Self: Sized, Self::Item: Stream,

Concatenates inner streams. Read more
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fn then<F, Fut>(self, f: F) -> Then<Self, F, Fut>
where Self: Sized, F: FnMut(Self::Item) -> Fut, Fut: Future,

Maps items of the stream to new values using an async closure. Read more
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fn filter<P>(self, predicate: P) -> Filter<Self, P>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Keeps items of the stream for which predicate returns true. Read more
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fn filter_map<T, F>(self, f: F) -> FilterMap<Self, F>
where Self: Sized, F: FnMut(Self::Item) -> Option<T>,

Filters and maps items of the stream using a closure. Read more
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fn take(self, n: usize) -> Take<Self>
where Self: Sized,

Takes only the first n items of the stream. Read more
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fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Takes items while predicate returns true. Read more
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fn skip(self, n: usize) -> Skip<Self>
where Self: Sized,

Skips the first n items of the stream. Read more
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fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Skips items while predicate returns true. Read more
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fn step_by(self, step: usize) -> StepBy<Self>
where Self: Sized,

Yields every stepth item. Read more
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fn chain<U>(self, other: U) -> Chain<Self, U>
where Self: Sized, U: Stream<Item = Self::Item>,

Appends another stream to the end of this one. Read more
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fn cloned<'a, T>(self) -> Cloned<Self>
where Self: Stream<Item = &'a T> + Sized, T: Clone + 'a,

Clones all items. Read more
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fn copied<'a, T>(self) -> Copied<Self>
where Self: Stream<Item = &'a T> + Sized, T: Copy + 'a,

Copies all items. Read more
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fn collect<C>(self) -> CollectFuture<Self, C> ⓘ
where Self: Sized, C: Default + Extend<Self::Item>,

Collects all items in the stream into a collection. Read more
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fn try_collect<T, E, C>(self) -> TryCollectFuture<Self, C> ⓘ
where Self: Stream<Item = Result<T, E>> + Sized, C: Default + Extend<T>,

Collects all items in the fallible stream into a collection. Read more
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fn partition<B, P>(self, predicate: P) -> PartitionFuture<Self, P, B> ⓘ
where Self: Sized, B: Default + Extend<Self::Item>, P: FnMut(&Self::Item) -> bool,

Partitions items into those for which predicate is true and those for which it is false, and then collects them into two collections. Read more
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fn fold<T, F>(self, init: T, f: F) -> FoldFuture<Self, F, T> ⓘ
where Self: Sized, F: FnMut(T, Self::Item) -> T,

Accumulates a computation over the stream. Read more
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fn try_fold<T, E, F, B>( &mut self, init: B, f: F ) -> TryFoldFuture<'_, Self, F, B> ⓘ
where Self: Stream<Item = Result<T, E>> + Unpin + Sized, F: FnMut(B, T) -> Result<B, E>,

Accumulates a fallible computation over the stream. Read more
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fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>
where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,

Maps items of the stream to new values using a state value and a closure. Read more
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fn fuse(self) -> Fuse<Self>
where Self: Sized,

Fuses the stream so that it stops yielding items after the first None. Read more
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fn cycle(self) -> Cycle<Self>
where Self: Clone + Sized,

Repeats the stream from beginning to end, forever. Read more
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fn enumerate(self) -> Enumerate<Self>
where Self: Sized,

Enumerates items, mapping them to (index, item). Read more
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fn inspect<F>(self, f: F) -> Inspect<Self, F>
where Self: Sized, F: FnMut(&Self::Item),

Calls a closure on each item and passes it on. Read more
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fn nth(&mut self, n: usize) -> NthFuture<'_, Self> ⓘ
where Self: Unpin,

Gets the nth item of the stream. Read more
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fn last(self) -> LastFuture<Self> ⓘ
where Self: Sized,

Returns the last item in the stream. Read more
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fn find<P>(&mut self, predicate: P) -> FindFuture<'_, Self, P> ⓘ
where Self: Unpin, P: FnMut(&Self::Item) -> bool,

Finds the first item of the stream for which predicate returns true. Read more
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fn find_map<F, B>(&mut self, f: F) -> FindMapFuture<'_, Self, F> ⓘ
where Self: Unpin, F: FnMut(Self::Item) -> Option<B>,

Applies a closure to items in the stream and returns the first Some result. Read more
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fn position<P>(&mut self, predicate: P) -> PositionFuture<'_, Self, P> ⓘ
where Self: Unpin, P: FnMut(Self::Item) -> bool,

Finds the index of the first item of the stream for which predicate returns true. Read more
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fn all<P>(&mut self, predicate: P) -> AllFuture<'_, Self, P> ⓘ
where Self: Unpin, P: FnMut(Self::Item) -> bool,

Tests if predicate returns true for all items in the stream. Read more
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fn any<P>(&mut self, predicate: P) -> AnyFuture<'_, Self, P> ⓘ
where Self: Unpin, P: FnMut(Self::Item) -> bool,

Tests if predicate returns true for any item in the stream. Read more
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fn for_each<F>(self, f: F) -> ForEachFuture<Self, F> ⓘ
where Self: Sized, F: FnMut(Self::Item),

Calls a closure on each item of the stream. Read more
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fn try_for_each<F, E>(&mut self, f: F) -> TryForEachFuture<'_, Self, F> ⓘ
where Self: Unpin, F: FnMut(Self::Item) -> Result<(), E>,

Calls a fallible closure on each item of the stream, stopping on first error. Read more
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fn zip<U>(self, other: U) -> Zip<Self, U>
where Self: Sized, U: Stream,

Zips up two streams into a single stream of pairs. Read more
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fn unzip<A, B, FromA, FromB>(self) -> UnzipFuture<Self, FromA, FromB> ⓘ
where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Stream<Item = (A, B)> + Sized,

Collects a stream of pairs into a pair of collections. Read more
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fn or<S>(self, other: S) -> Or<Self, S>
where Self: Sized, S: Stream<Item = Self::Item>,

Merges with other stream, preferring items from self whenever both streams are ready. Read more
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fn race<S>(self, other: S) -> Race<Self, S>
where Self: Sized, S: Stream<Item = Self::Item>,

Merges with other stream, with no preference for either stream when both are ready. Read more
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fn boxed<'a>(self) -> Pin<Box<dyn Stream<Item = Self::Item> + Send + 'a>>
where Self: Send + Sized + 'a,

Boxes the stream and changes its type to dyn Stream + Send + 'a. Read more
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fn boxed_local<'a>(self) -> Pin<Box<dyn Stream<Item = Self::Item> + 'a>>
where Self: Sized + 'a,

Boxes the stream and changes its type to dyn Stream + 'a. Read more
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impl<T> StreamExt for T
where T: Stream + ?Sized,

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fn next(&mut self) -> NextFuture<'_, Self>
where Self: Unpin,

Advances the stream and returns the next value. Read more
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fn take(self, n: usize) -> Take<Self>
where Self: Sized,

Creates a stream that yields its first n elements. Read more
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fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates a stream that yields elements based on a predicate. Read more
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fn throttle(self, d: Duration) -> Throttle<Self>
where Self: Sized,

Limit the amount of items yielded per timeslice in a stream. Read more
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fn step_by(self, step: usize) -> StepBy<Self>
where Self: Sized,

Creates a stream that yields each stepth element. Read more
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fn chain<U>(self, other: U) -> Chain<Self, U>
where Self: Sized, U: Stream<Item = Self::Item> + Sized,

Takes two streams and creates a new stream over both in sequence. Read more
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fn cloned<'a, T>(self) -> Cloned<Self>
where Self: Sized + Stream<Item = &'a T>, T: Clone + 'a,

Creates an stream which copies all of its elements. Read more
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fn copied<'a, T>(self) -> Copied<Self>
where Self: Sized + Stream<Item = &'a T>, T: Copy + 'a,

Creates an stream which copies all of its elements. Read more
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fn cycle(self) -> Cycle<Self>
where Self: Clone + Sized,

Creates a stream that yields the provided values infinitely and in order. Read more
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fn enumerate(self) -> Enumerate<Self>
where Self: Sized,

Creates a stream that gives the current element’s count as well as the next value. Read more
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fn delay(self, dur: Duration) -> Delay<Self>
where Self: Sized,

Creates a stream that is delayed before it starts yielding items. Read more
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fn map<B, F>(self, f: F) -> Map<Self, F>
where Self: Sized, F: FnMut(Self::Item) -> B,

Takes a closure and creates a stream that calls that closure on every element of this stream. Read more
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fn inspect<F>(self, f: F) -> Inspect<Self, F>
where Self: Sized, F: FnMut(&Self::Item),

A combinator that does something with each element in the stream, passing the value on. Read more
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fn last(self) -> LastFuture<Self, Self::Item>
where Self: Sized,

Returns the last element of the stream. Read more
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fn fuse(self) -> Fuse<Self>
where Self: Sized,

Creates a stream which ends after the first None. Read more
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fn filter<P>(self, predicate: P) -> Filter<Self, P>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates a stream that uses a predicate to determine if an element should be yielded. Read more
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fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
where Self: Sized, U: IntoStream, F: FnMut(Self::Item) -> U,

Creates an stream that works like map, but flattens nested structure. Read more
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fn flatten(self) -> Flatten<Self>
where Self: Sized, Self::Item: IntoStream,

Creates an stream that flattens nested structure. Read more
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fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Both filters and maps a stream. Read more
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fn min_by_key<B, F>(self, key_by: F) -> MinByKeyFuture<Self, Self::Item, F>
where Self: Sized, B: Ord, F: FnMut(&Self::Item) -> B,

Returns the element that gives the minimum value with respect to the specified key function. If several elements are equally minimum, the first element is returned. If the stream is empty, None is returned. Read more
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fn max_by_key<B, F>(self, key_by: F) -> MaxByKeyFuture<Self, Self::Item, F>
where Self: Sized, B: Ord, F: FnMut(&Self::Item) -> B,

Returns the element that gives the maximum value with respect to the specified key function. If several elements are equally maximum, the first element is returned. If the stream is empty, None is returned. Read more
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fn min_by<F>(self, compare: F) -> MinByFuture<Self, F, Self::Item>
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function. If several elements are equally minimum, the first element is returned. If the stream is empty, None is returned. Read more
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fn max(self) -> MaxFuture<Self, Self::Item>
where Self: Sized, Self::Item: Ord,

Returns the element that gives the maximum value. If several elements are equally maximum, the first element is returned. If the stream is empty, None is returned. Read more
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fn min(self) -> MinFuture<Self, Self::Item>
where Self: Sized, Self::Item: Ord,

Returns the element that gives the minimum value. If several elements are equally minimum, the first element is returned. If the stream is empty, None is returned. Read more
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fn max_by<F>(self, compare: F) -> MaxByFuture<Self, F, Self::Item>
where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function. If several elements are equally maximum, the first element is returned. If the stream is empty, None is returned. Read more
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fn nth(&mut self, n: usize) -> NthFuture<'_, Self>
where Self: Unpin + Sized,

Returns the nth element of the stream. Read more
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fn all<F>(&mut self, f: F) -> AllFuture<'_, Self, F, Self::Item>
where Self: Unpin + Sized, F: FnMut(Self::Item) -> bool,

Tests if every element of the stream matches a predicate. Read more
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fn find<P>(&mut self, p: P) -> FindFuture<'_, Self, P>
where Self: Unpin + Sized, P: FnMut(&Self::Item) -> bool,

Searches for an element in a stream that satisfies a predicate. Read more
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fn find_map<F, B>(&mut self, f: F) -> FindMapFuture<'_, Self, F>
where Self: Unpin + Sized, F: FnMut(Self::Item) -> Option<B>,

Applies function to the elements of stream and returns the first non-none result. Read more
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fn fold<B, F>(self, init: B, f: F) -> FoldFuture<Self, F, B>
where Self: Sized, F: FnMut(B, Self::Item) -> B,

A combinator that applies a function to every element in a stream producing a single, final value. Read more
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fn partition<B, F>(self, f: F) -> PartitionFuture<Self, F, B>
where Self: Sized, F: FnMut(&Self::Item) -> bool, B: Default + Extend<Self::Item>,

A combinator that applies a function to every element in a stream creating two collections from it. Read more
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fn for_each<F>(self, f: F) -> ForEachFuture<Self, F>
where Self: Sized, F: FnMut(Self::Item),

Call a closure on each element of the stream. Read more
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fn any<F>(&mut self, f: F) -> AnyFuture<'_, Self, F, Self::Item>
where Self: Unpin + Sized, F: FnMut(Self::Item) -> bool,

Tests if any element of the stream matches a predicate. Read more
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fn by_ref(&mut self) -> &mut Self

Borrows an stream, rather than consuming it. Read more
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fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>
where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,

A stream adaptor similar to fold that holds internal state and produces a new stream. Read more
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fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
where Self: Sized, P: FnMut(&Self::Item) -> bool,

Combinator that skips elements based on a predicate. Read more
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fn skip(self, n: usize) -> Skip<Self>
where Self: Sized,

Creates a combinator that skips the first n elements. Read more
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fn timeout(self, dur: Duration) -> Timeout<Self>
where Self: Stream + Sized,

Await a stream or times out after a duration of time. Read more
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fn try_fold<B, F, T, E>( &mut self, init: T, f: F ) -> TryFoldFuture<'_, Self, F, T>
where Self: Unpin + Sized, F: FnMut(B, Self::Item) -> Result<T, E>,

A combinator that applies a function as long as it returns successfully, producing a single, final value. Immediately returns the error when the function returns unsuccessfully. Read more
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fn try_for_each<F, E>(&mut self, f: F) -> TryForEachFuture<'_, Self, F>
where Self: Unpin + Sized, F: FnMut(Self::Item) -> Result<(), E>,

Applies a falliable function to each element in a stream, stopping at first error and returning it. Read more
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fn zip<U>(self, other: U) -> Zip<Self, U>
where Self: Sized, U: Stream,

‘Zips up’ two streams into a single stream of pairs. Read more
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fn unzip<A, B, FromA, FromB>(self) -> UnzipFuture<Self, FromA, FromB>
where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Stream<Item = (A, B)> + Sized,

Converts an stream of pairs into a pair of containers. Read more
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fn collect<'a, B>(self) -> Pin<Box<dyn Future<Output = B> + Send + 'a>>
where Self: Sized + 'a + Send, B: FromStream<Self::Item>, Self::Item: Send,

Transforms a stream into a collection. Read more
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fn merge<U>(self, other: U) -> Merge<Self, U>
where Self: Sized, U: Stream<Item = Self::Item> + Sized,

Combines multiple streams into a single stream of all their outputs. Read more
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fn partial_cmp<S>(self, other: S) -> PartialCmpFuture<Self, S>
where Self: Sized + Stream, S: Stream, <Self as Stream>::Item: PartialOrd<S::Item>,

Lexicographically compares the elements of this Stream with those of another. Read more
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fn position<P>(&mut self, predicate: P) -> PositionFuture<'_, Self, P>
where Self: Unpin + Sized, P: FnMut(Self::Item) -> bool,

Searches for an element in a Stream that satisfies a predicate, returning its index. Read more
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fn cmp<S>(self, other: S) -> CmpFuture<Self, S>
where Self: Sized + Stream, S: Stream, <Self as Stream>::Item: Ord,

Lexicographically compares the elements of this Stream with those of another using ‘Ord’. Read more
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fn count(self) -> CountFuture<Self>
where Self: Sized,

Counts the number of elements in the stream. Read more
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fn ne<S>(self, other: S) -> NeFuture<Self, S>
where Self: Sized, S: Sized + Stream, <Self as Stream>::Item: PartialEq<S::Item>,

Determines if the elements of this Stream are lexicographically not equal to those of another. Read more
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fn ge<S>(self, other: S) -> GeFuture<Self, S>
where Self: Sized + Stream, S: Stream, <Self as Stream>::Item: PartialOrd<S::Item>,

Determines if the elements of this Stream are lexicographically greater than or equal to those of another. Read more
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fn eq<S>(self, other: S) -> EqFuture<Self, S>
where Self: Sized + Stream, S: Sized + Stream, <Self as Stream>::Item: PartialEq<S::Item>,

Determines if the elements of this Stream are lexicographically equal to those of another. Read more
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fn gt<S>(self, other: S) -> GtFuture<Self, S>
where Self: Sized + Stream, S: Stream, <Self as Stream>::Item: PartialOrd<S::Item>,

Determines if the elements of this Stream are lexicographically greater than those of another. Read more
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fn le<S>(self, other: S) -> LeFuture<Self, S>
where Self: Sized + Stream, S: Stream, <Self as Stream>::Item: PartialOrd<S::Item>,

Determines if the elements of this Stream are lexicographically less or equal to those of another. Read more
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fn lt<S>(self, other: S) -> LtFuture<Self, S>
where Self: Sized + Stream, S: Stream, <Self as Stream>::Item: PartialOrd<S::Item>,

Determines if the elements of this Stream are lexicographically less than those of another. Read more
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fn sum<'a, S>(self) -> Pin<Box<dyn Future<Output = S> + 'a>>
where Self: Sized + Stream<Item = S> + 'a, S: Sum<Self::Item>,

Sums the elements of a stream. Read more
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fn product<'a, P>(self) -> Pin<Box<dyn Future<Output = P> + 'a>>
where Self: Sized + Stream<Item = P> + 'a, P: Product,

Multiplies all elements of the stream. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<S, T, E> TryStream for S
where S: Stream<Item = Result<T, E>> + ?Sized,

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type Ok = T

The type of successful values yielded by this future
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type Error = E

The type of failures yielded by this future
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fn try_poll_next( self: Pin<&mut S>, cx: &mut Context<'_> ) -> Poll<Option<Result<<S as TryStream>::Ok, <S as TryStream>::Error>>>

Poll this TryStream as if it were a Stream. Read more