Trait core::iter::Sum1.12.0[][src]

pub trait Sum<A = Self>: Sized {
    fn sum<I: Iterator<Item = A>>(iter: I) -> Self;

Trait to represent types that can be created by summing up an iterator.

This trait is used to implement the sum() method on iterators. Types which implement the trait can be generated by the sum() method. Like FromIterator this trait should rarely be called directly and instead interacted with through Iterator::sum().

Required methods

fn sum<I: Iterator<Item = A>>(iter: I) -> Self[src]

Method which takes an iterator and generates Self from the elements by “summing up” the items.

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impl Sum<Wrapping<i8>> for Wrapping<i8>1.14.0[src]

impl Sum<Wrapping<i16>> for Wrapping<i16>1.14.0[src]

impl Sum<Wrapping<i32>> for Wrapping<i32>1.14.0[src]

impl Sum<Wrapping<i64>> for Wrapping<i64>1.14.0[src]

impl Sum<Wrapping<i128>> for Wrapping<i128>1.14.0[src]

impl Sum<Wrapping<isize>> for Wrapping<isize>1.14.0[src]

impl Sum<Wrapping<u8>> for Wrapping<u8>1.14.0[src]

impl Sum<Wrapping<u16>> for Wrapping<u16>1.14.0[src]

impl Sum<Wrapping<u32>> for Wrapping<u32>1.14.0[src]

impl Sum<Wrapping<u64>> for Wrapping<u64>1.14.0[src]

impl Sum<Wrapping<u128>> for Wrapping<u128>1.14.0[src]

impl Sum<Wrapping<usize>> for Wrapping<usize>1.14.0[src]

impl Sum<Duration> for Duration1.16.0[src]

impl Sum<f32> for f32[src]

impl Sum<f64> for f64[src]

impl Sum<i8> for i8[src]

impl Sum<i16> for i16[src]

impl Sum<i32> for i32[src]

impl Sum<i64> for i64[src]

impl Sum<i128> for i128[src]

impl Sum<isize> for isize[src]

impl Sum<u8> for u8[src]

impl Sum<u16> for u16[src]

impl Sum<u32> for u32[src]

impl Sum<u64> for u64[src]

impl Sum<u128> for u128[src]

impl Sum<usize> for usize[src]

impl<'a> Sum<&'a Wrapping<i8>> for Wrapping<i8>1.14.0[src]

impl<'a> Sum<&'a Wrapping<i16>> for Wrapping<i16>1.14.0[src]

impl<'a> Sum<&'a Wrapping<i32>> for Wrapping<i32>1.14.0[src]

impl<'a> Sum<&'a Wrapping<i64>> for Wrapping<i64>1.14.0[src]

impl<'a> Sum<&'a Wrapping<i128>> for Wrapping<i128>1.14.0[src]

impl<'a> Sum<&'a Wrapping<isize>> for Wrapping<isize>1.14.0[src]

impl<'a> Sum<&'a Wrapping<u8>> for Wrapping<u8>1.14.0[src]

impl<'a> Sum<&'a Wrapping<u16>> for Wrapping<u16>1.14.0[src]

impl<'a> Sum<&'a Wrapping<u32>> for Wrapping<u32>1.14.0[src]

impl<'a> Sum<&'a Wrapping<u64>> for Wrapping<u64>1.14.0[src]

impl<'a> Sum<&'a Wrapping<u128>> for Wrapping<u128>1.14.0[src]

impl<'a> Sum<&'a Wrapping<usize>> for Wrapping<usize>1.14.0[src]

impl<'a> Sum<&'a Duration> for Duration1.16.0[src]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

impl<T, U> Sum<Option<U>> for Option<T> where
    T: Sum<U>, 

fn sum<I>(iter: I) -> Option<T> where
    I: Iterator<Item = Option<U>>, 

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.


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:

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

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

fn sum<I>(iter: I) -> Result<T, E> where
    I: Iterator<Item = Result<U, E>>, 

Takes each element in the Iterator: 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.


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

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