Trait stdcli::prelude::itertools::__std_iter::Sum 1.12.0
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pub trait Sum<A = Self> { fn sum<I>(iter: I) -> Self
where
I: Iterator<Item = A>; }
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>(iter: I) -> Self where
I: Iterator<Item = A>,
I: Iterator<Item = A>,
Method which takes an iterator and generates Self
from the elements by
"summing up" the items.
Implementations on Foreign Types
impl<'a> Sum<&'a f64> for f64
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impl Sum<i8> for i8
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impl<'a> Sum<&'a i64> for i64
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impl Sum<Wrapping<i32>> for Wrapping<i32>
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impl<'a> Sum<&'a Wrapping<u16>> for Wrapping<u16>
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impl<'a> Sum<&'a Wrapping<u8>> for Wrapping<u8>
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impl Sum<i16> for i16
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impl<'a> Sum<&'a Wrapping<isize>> for Wrapping<isize>
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impl<'a> Sum<&'a u128> for u128
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impl<'a> Sum<&'a i128> for i128
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impl Sum<usize> for usize
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impl<'a> Sum<&'a isize> for isize
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impl Sum<Wrapping<i128>> for Wrapping<i128>
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impl Sum<u32> for u32
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impl Sum<i32> for i32
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impl Sum<u8> for u8
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impl Sum<Wrapping<u32>> for Wrapping<u32>
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impl<T, U, E> Sum<Result<U, E>> for Result<T, E> where
T: Sum<U>,
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T: Sum<U>,
fn sum<I>(iter: I) -> Result<T, E> where
I: Iterator<Item = Result<U, E>>,
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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.
Examples
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) } ).sum(); assert_eq!(res, Ok(3));