[−][src]Trait async_std::stream::Sum

pub trait Sum<A = Self>: Sized {
    fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'a>>
    where
        S: Stream<Item = A> + 'a;
}
This is supported on unstable only.

Trait to represent types that can be created by summing up a stream.

This trait is used to implement the sum method on streams. Types which implement the trait can be generated by the sum method. Like FromStream this trait should rarely be called directly and instead interacted with through Stream::sum.

Required methods

ⓘImportant traits for Pin<P>
fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'a>> where
    S: Stream<Item = A> + 'a, 

This is supported on unstable only.

Method which takes a stream and generates Self from the elements by "summing up" the items.

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Implementations on Foreign Types

impl Sum<i8> for i8[src]

impl<'a> Sum<&'a i8> for i8[src]

impl Sum<i16> for i16[src]

impl<'a> Sum<&'a i16> for i16[src]

impl Sum<i32> for i32[src]

impl<'a> Sum<&'a i32> for i32[src]

impl Sum<i64> for i64[src]

impl<'a> Sum<&'a i64> for i64[src]

impl Sum<i128> for i128[src]

impl<'a> Sum<&'a i128> for i128[src]

impl Sum<isize> for isize[src]

impl<'a> Sum<&'a isize> for isize[src]

impl Sum<u8> for u8[src]

impl<'a> Sum<&'a u8> for u8[src]

impl Sum<u16> for u16[src]

impl<'a> Sum<&'a u16> for u16[src]

impl Sum<u32> for u32[src]

impl<'a> Sum<&'a u32> for u32[src]

impl Sum<u64> for u64[src]

impl<'a> Sum<&'a u64> for u64[src]

impl Sum<u128> for u128[src]

impl<'a> Sum<&'a u128> for u128[src]

impl Sum<usize> for usize[src]

impl<'a> Sum<&'a usize> for usize[src]

impl Sum<Wrapping<i8>> for Wrapping<i8>[src]

impl<'a> Sum<&'a Wrapping<i8>> for Wrapping<i8>[src]

impl Sum<Wrapping<i16>> for Wrapping<i16>[src]

impl<'a> Sum<&'a Wrapping<i16>> for Wrapping<i16>[src]

impl Sum<Wrapping<i32>> for Wrapping<i32>[src]

impl<'a> Sum<&'a Wrapping<i32>> for Wrapping<i32>[src]

impl Sum<Wrapping<i64>> for Wrapping<i64>[src]

impl<'a> Sum<&'a Wrapping<i64>> for Wrapping<i64>[src]

impl Sum<Wrapping<i128>> for Wrapping<i128>[src]

impl<'a> Sum<&'a Wrapping<i128>> for Wrapping<i128>[src]

impl Sum<Wrapping<isize>> for Wrapping<isize>[src]

impl<'a> Sum<&'a Wrapping<isize>> for Wrapping<isize>[src]

impl Sum<Wrapping<u8>> for Wrapping<u8>[src]

impl<'a> Sum<&'a Wrapping<u8>> for Wrapping<u8>[src]

impl Sum<Wrapping<u16>> for Wrapping<u16>[src]

impl<'a> Sum<&'a Wrapping<u16>> for Wrapping<u16>[src]

impl Sum<Wrapping<u32>> for Wrapping<u32>[src]

impl<'a> Sum<&'a Wrapping<u32>> for Wrapping<u32>[src]

impl Sum<Wrapping<u64>> for Wrapping<u64>[src]

impl<'a> Sum<&'a Wrapping<u64>> for Wrapping<u64>[src]

impl Sum<Wrapping<u128>> for Wrapping<u128>[src]

impl<'a> Sum<&'a Wrapping<u128>> for Wrapping<u128>[src]

impl Sum<Wrapping<usize>> for Wrapping<usize>[src]

impl<'a> Sum<&'a Wrapping<usize>> for Wrapping<usize>[src]

impl Sum<f32> for f32[src]

impl<'a> Sum<&'a f32> for f32[src]

impl Sum<f64> for f64[src]

impl<'a> Sum<&'a f64> for f64[src]

impl<T, U, E> Sum<Result<U, E>> for Result<T, E> where
    T: Sum<U>, [src]

ⓘImportant traits for Pin<P>
fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Result<T, E>> + 'a>> where
    S: Stream<Item = Result<U, E>> + 'a, [src]

This is supported on unstable and unstable only.

Takes each element in the Stream: if it is an Err, no further elements are taken, and the Err is returned. Should no Err occur, the sum of all elements is returned.

Examples

This sums up every integer in a vector, rejecting the sum if a negative element is encountered:

use async_std::prelude::*;
use async_std::stream;

let v = stream::from_iter(vec![1, 2]);
let res: Result<i32, &'static str> = v.map(|x|
    if x < 0 {
        Err("Negative element found")
    } else {
        Ok(x)
    }).sum().await;
assert_eq!(res, Ok(3));

impl<T, U> Sum<Option<U>> for Option<T> where
    T: Sum<U>, [src]

ⓘImportant traits for Pin<P>
fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Option<T>> + 'a>> where
    S: Stream<Item = Option<U>> + 'a, [src]

This is supported on unstable and unstable only.

Takes each element in the Iterator: if it is a None, no further elements are taken, and the None is returned. Should no None occur, the sum of all elements is returned.

Examples

This sums up the position of the character 'a' in a vector of strings, if a word did not have the character 'a' the operation returns None:

use async_std::prelude::*;
use async_std::stream;

let words = stream::from_iter(vec!["have", "a", "great", "day"]);
let total: Option<usize> = words.map(|w| w.find('a')).sum().await;
assert_eq!(total, Some(5));
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Implementors

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