Trait Tools 

pub trait Tools<Item>
where
    Self: Stream<Item = Item> + Send + Sized,
    <Self as Stream>::Item: Send,
{
    // Required methods
    fn counts(self) -> impl Future<Output = HashMap<Item, usize>> + Send
       where <Self as Stream>::Item: Eq + Hash;
    fn counts_by<K, F>(
        self,
        f: F,
    ) -> impl Future<Output = HashMap<K, usize>> + Send
       where F: Fn(Item) -> K + Send,
             K: Eq + Hash + Send;
    fn counts_by_with_cap<const CAP: usize, K, F>(
        self,
        f: F,
    ) -> impl Future<Output = HashMap<K, usize>> + Send
       where F: Fn(Item) -> K + Send,
             K: Eq + Hash + Send;
    fn counts_with_cap<const CAP: usize>(
        self,
    ) -> impl Future<Output = HashMap<Item, usize>> + Send
       where <Self as Stream>::Item: Eq + Hash;
    fn sample_by<const N: usize, K, F>(
        self,
        f: F,
    ) -> impl Future<Output = ArrayVec<K, N>> + Send
       where F: Fn(Item) -> K + Send,
             K: Send;
    fn fold_default<T, F, Fut>(self, f: F) -> impl Future<Output = T> + Send
       where F: Fn(T, Item) -> Fut + Send,
             Fut: Future<Output = T> + Send,
             T: Default + Send;
}

Adds aggregation, sampling, and folding operations to streams.

Counting adapters consume the source into hash maps, while folding avoids an intermediate collection. Reservoir sampling retains a uniform subset of up to a fixed size in one pass.

Required Methods

fn counts(self) -> impl Future<Output = HashMap<Item, usize>> + Send

where <Self as Stream>::Item: Eq + Hash,

Counts occurrences of each distinct stream item.

The entire stream is consumed into a hash map that starts at zero capacity and grows as needed. Equal items share one incrementing counter.

Panics

Panics if an item’s occurrence count overflows usize.

fn counts_by<K, F>(self, f: F) -> impl Future<Output = HashMap<K, usize>> + Send

where F: Fn(Item) -> K + Send, K: Eq + Hash + Send,

Counts occurrences of keys derived from stream items.

f is applied once to every item before counting. The result map starts at zero capacity and grows as needed.

Panics

Panics if a derived key’s occurrence count overflows usize.

fn counts_by_with_cap<const CAP: usize, K, F>( self, f: F, ) -> impl Future<Output = HashMap<K, usize>> + Send

where F: Fn(Item) -> K + Send, K: Eq + Hash + Send,

Counts derived keys into a map with initial capacity CAP.

f is applied once to every stream item. The map initially reserves space for at least CAP distinct keys and grows as needed.

Panics

Panics if a derived key’s occurrence count overflows usize.

fn counts_with_cap<const CAP: usize>( self, ) -> impl Future<Output = HashMap<Item, usize>> + Send

where <Self as Stream>::Item: Eq + Hash,

Counts items into a map with initial capacity CAP.

Equal items share one counter as the entire stream is consumed. The map initially reserves space for at least CAP distinct items and grows as needed.

Panics

Panics if an item’s occurrence count overflows usize.

fn sample_by<const N: usize, K, F>( self, f: F, ) -> impl Future<Output = ArrayVec<K, N>> + Send

where F: Fn(Item) -> K + Send, K: Send,

Reservoir-samples up to N items uniformly without replacement.

The stream is consumed in one pass, and f is applied only when an item enters the reservoir, including entries later replaced. Rejected items do not invoke it, and derived keys may repeat.

Panics

Panics if the number of observed stream items overflows usize.

fn fold_default<T, F, Fut>(self, f: F) -> impl Future<Output = T> + Send

where F: Fn(T, Item) -> Fut + Send, Fut: Future<Output = T> + Send, T: Default + Send,

Folds the stream from T::default() with an asynchronous accumulator.

Each item is processed in source order after the previous fold future resolves. The final accumulator is returned when the stream ends.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl<Item, S> Tools<Item> for S

where S: Stream<Item = Item> + Send + Sized, <Self as Stream>::Item: Send,