Trait sp_std::iter::Iterator

#[must_use = "iterators are lazy and do nothing unless consumed"]pub trait Iterator {
    type Item;
#[lang = "next"]    pub fn next(&mut self) -> Option<Self::Item>;

    pub fn size_hint(&self) -> (usize, Option<usize>) { ... }
    pub fn count(self) -> usize { ... }
    pub fn last(self) -> Option<Self::Item> { ... }
    pub fn advance_by(&mut self, n: usize) -> Result<(), usize> { ... }
    pub fn nth(&mut self, n: usize) -> Option<Self::Item> { ... }
    pub fn step_by(self, step: usize) -> StepBy<Self> { ... }
    pub fn chain<U>(
        self, 
        other: U
    ) -> Chain<Self, <U as IntoIterator>::IntoIter>
    where
        U: IntoIterator<Item = Self::Item>,
    { ... }
    pub fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>
    where
        U: IntoIterator,
    { ... }
    pub fn intersperse(self, separator: Self::Item) -> Intersperse<Self>
    where
        Self::Item: Clone,
    { ... }
    pub fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>
    where
        G: FnMut() -> Self::Item,
    { ... }
    pub fn map<B, F>(self, f: F) -> Map<Self, F>
    where
        F: FnMut(Self::Item) -> B,
    { ... }
    pub fn for_each<F>(self, f: F)
    where
        F: FnMut(Self::Item),
    { ... }
    pub fn filter<P>(self, predicate: P) -> Filter<Self, P>
    where
        P: FnMut(&Self::Item) -> bool,
    { ... }
    pub fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
    where
        F: FnMut(Self::Item) -> Option<B>,
    { ... }
    pub fn enumerate(self) -> Enumerate<Self> { ... }
    pub fn peekable(self) -> Peekable<Self> { ... }
    pub fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>
    where
        P: FnMut(&Self::Item) -> bool,
    { ... }
    pub fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>
    where
        P: FnMut(&Self::Item) -> bool,
    { ... }
    pub fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>
    where
        P: FnMut(Self::Item) -> Option<B>,
    { ... }
    pub fn skip(self, n: usize) -> Skip<Self> { ... }
    pub fn take(self, n: usize) -> Take<Self> { ... }
    pub fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>
    where
        F: FnMut(&mut St, Self::Item) -> Option<B>,
    { ... }
    pub fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>
    where
        F: FnMut(Self::Item) -> U,
        U: IntoIterator,
    { ... }
    pub fn flatten(self) -> Flatten<Self>
    where
        Self::Item: IntoIterator,
    { ... }
    pub fn fuse(self) -> Fuse<Self> { ... }
    pub fn inspect<F>(self, f: F) -> Inspect<Self, F>
    where
        F: FnMut(&Self::Item),
    { ... }
    pub fn by_ref(&mut self) -> &mut Self { ... }
#[must_use =
  "if you really need to exhaust the iterator, consider `.for_each(drop)` instead"]    pub fn collect<B>(self) -> B
    where
        B: FromIterator<Self::Item>,
    { ... }
    pub fn partition<B, F>(self, f: F) -> (B, B)
    where
        F: FnMut(&Self::Item) -> bool,
        B: Default + Extend<Self::Item>,
    { ... }
    pub fn partition_in_place<'a, T, P>(self, predicate: P) -> usize
    where
        Self: DoubleEndedIterator<Item = &'a mut T>,
        T: 'a,
        P: FnMut(&T) -> bool,
    { ... }
    pub fn is_partitioned<P>(self, predicate: P) -> bool
    where
        P: FnMut(Self::Item) -> bool,
    { ... }
    pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
    where
        R: Try<Ok = B>,
        F: FnMut(B, Self::Item) -> R,
    { ... }
    pub fn try_for_each<F, R>(&mut self, f: F) -> R
    where
        R: Try<Ok = ()>,
        F: FnMut(Self::Item) -> R,
    { ... }
    pub fn fold<B, F>(self, init: B, f: F) -> B
    where
        F: FnMut(B, Self::Item) -> B,
    { ... }
    pub fn fold_first<F>(self, f: F) -> Option<Self::Item>
    where
        F: FnMut(Self::Item, Self::Item) -> Self::Item,
    { ... }
    pub fn all<F>(&mut self, f: F) -> bool
    where
        F: FnMut(Self::Item) -> bool,
    { ... }
    pub fn any<F>(&mut self, f: F) -> bool
    where
        F: FnMut(Self::Item) -> bool,
    { ... }
    pub fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
    where
        P: FnMut(&Self::Item) -> bool,
    { ... }
    pub fn find_map<B, F>(&mut self, f: F) -> Option<B>
    where
        F: FnMut(Self::Item) -> Option<B>,
    { ... }
    pub fn try_find<F, R>(
        &mut self, 
        f: F
    ) -> Result<Option<Self::Item>, <R as Try>::Error>
    where
        R: Try<Ok = bool>,
        F: FnMut(&Self::Item) -> R,
    { ... }
    pub fn position<P>(&mut self, predicate: P) -> Option<usize>
    where
        P: FnMut(Self::Item) -> bool,
    { ... }
    pub fn rposition<P>(&mut self, predicate: P) -> Option<usize>
    where
        Self: ExactSizeIterator + DoubleEndedIterator,
        P: FnMut(Self::Item) -> bool,
    { ... }
    pub fn max(self) -> Option<Self::Item>
    where
        Self::Item: Ord,
    { ... }
    pub fn min(self) -> Option<Self::Item>
    where
        Self::Item: Ord,
    { ... }
    pub fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>
    where
        F: FnMut(&Self::Item) -> B,
        B: Ord,
    { ... }
    pub fn max_by<F>(self, compare: F) -> Option<Self::Item>
    where
        F: FnMut(&Self::Item, &Self::Item) -> Ordering,
    { ... }
    pub fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>
    where
        F: FnMut(&Self::Item) -> B,
        B: Ord,
    { ... }
    pub fn min_by<F>(self, compare: F) -> Option<Self::Item>
    where
        F: FnMut(&Self::Item, &Self::Item) -> Ordering,
    { ... }
    pub fn rev(self) -> Rev<Self>
    where
        Self: DoubleEndedIterator,
    { ... }
    pub fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
    where
        Self: Iterator<Item = (A, B)>,
        FromA: Default + Extend<A>,
        FromB: Default + Extend<B>,
    { ... }
    pub fn copied<'a, T>(self) -> Copied<Self>
    where
        Self: Iterator<Item = &'a T>,
        T: 'a + Copy,
    { ... }
    pub fn cloned<'a, T>(self) -> Cloned<Self>
    where
        Self: Iterator<Item = &'a T>,
        T: 'a + Clone,
    { ... }
    pub fn cycle(self) -> Cycle<Self>
    where
        Self: Clone,
    { ... }
    pub fn sum<S>(self) -> S
    where
        S: Sum<Self::Item>,
    { ... }
    pub fn product<P>(self) -> P
    where
        P: Product<Self::Item>,
    { ... }
    pub fn cmp<I>(self, other: I) -> Ordering
    where
        I: IntoIterator<Item = Self::Item>,
        Self::Item: Ord,
    { ... }
    pub fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
    where
        F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
        I: IntoIterator,
    { ... }
    pub fn partial_cmp<I>(self, other: I) -> Option<Ordering>
    where
        I: IntoIterator,
        Self::Item: PartialOrd<<I as IntoIterator>::Item>,
    { ... }
    pub fn partial_cmp_by<I, F>(
        self, 
        other: I, 
        partial_cmp: F
    ) -> Option<Ordering>
    where
        F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
        I: IntoIterator,
    { ... }
    pub fn eq<I>(self, other: I) -> bool
    where
        I: IntoIterator,
        Self::Item: PartialEq<<I as IntoIterator>::Item>,
    { ... }
    pub fn eq_by<I, F>(self, other: I, eq: F) -> bool
    where
        F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
        I: IntoIterator,
    { ... }
    pub fn ne<I>(self, other: I) -> bool
    where
        I: IntoIterator,
        Self::Item: PartialEq<<I as IntoIterator>::Item>,
    { ... }
    pub fn lt<I>(self, other: I) -> bool
    where
        I: IntoIterator,
        Self::Item: PartialOrd<<I as IntoIterator>::Item>,
    { ... }
    pub fn le<I>(self, other: I) -> bool
    where
        I: IntoIterator,
        Self::Item: PartialOrd<<I as IntoIterator>::Item>,
    { ... }
    pub fn gt<I>(self, other: I) -> bool
    where
        I: IntoIterator,
        Self::Item: PartialOrd<<I as IntoIterator>::Item>,
    { ... }
    pub fn ge<I>(self, other: I) -> bool
    where
        I: IntoIterator,
        Self::Item: PartialOrd<<I as IntoIterator>::Item>,
    { ... }
    pub fn is_sorted(self) -> bool
    where
        Self::Item: PartialOrd<Self::Item>,
    { ... }
    pub fn is_sorted_by<F>(self, compare: F) -> bool
    where
        F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
    { ... }
    pub fn is_sorted_by_key<F, K>(self, f: F) -> bool
    where
        K: PartialOrd<K>,
        F: FnMut(Self::Item) -> K,
    { ... }
}

An interface for dealing with iterators.

This is the main iterator trait. For more about the concept of iterators generally, please see the module-level documentation. In particular, you may want to know how to implement Iterator.

Associated Types

type Item

The type of the elements being iterated over.

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Required methods

#[lang = "next"]pub fn next(&mut self) -> Option<Self::Item>

Advances the iterator and returns the next value.

Returns None when iteration is finished. Individual iterator implementations may choose to resume iteration, and so calling next() again may or may not eventually start returning Some(Item) again at some point.

Examples

Basic usage:

let a = [1, 2, 3];

let mut iter = a.iter();

// A call to next() returns the next value...
assert_eq!(Some(&1), iter.next());
assert_eq!(Some(&2), iter.next());
assert_eq!(Some(&3), iter.next());

// ... and then None once it's over.
assert_eq!(None, iter.next());

// More calls may or may not return `None`. Here, they always will.
assert_eq!(None, iter.next());
assert_eq!(None, iter.next());

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Provided methods

pub fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator.

Specifically, size_hint() returns a tuple where the first element is the lower bound, and the second element is the upper bound.

The second half of the tuple that is returned is an Option<usize>. A None here means that either there is no known upper bound, or the upper bound is larger than usize.

Implementation notes

It is not enforced that an iterator implementation yields the declared number of elements. A buggy iterator may yield less than the lower bound or more than the upper bound of elements.

size_hint() is primarily intended to be used for optimizations such as reserving space for the elements of the iterator, but must not be trusted to e.g., omit bounds checks in unsafe code. An incorrect implementation of size_hint() should not lead to memory safety violations.

That said, the implementation should provide a correct estimation, because otherwise it would be a violation of the trait's protocol.

The default implementation returns (0, None) which is correct for any iterator.

Examples

Basic usage:

let a = [1, 2, 3];
let iter = a.iter();

assert_eq!((3, Some(3)), iter.size_hint());

A more complex example:

// The even numbers from zero to ten.
let iter = (0..10).filter(|x| x % 2 == 0);

// We might iterate from zero to ten times. Knowing that it's five
// exactly wouldn't be possible without executing filter().
assert_eq!((0, Some(10)), iter.size_hint());

// Let's add five more numbers with chain()
let iter = (0..10).filter(|x| x % 2 == 0).chain(15..20);

// now both bounds are increased by five
assert_eq!((5, Some(15)), iter.size_hint());

Returning None for an upper bound:

// an infinite iterator has no upper bound
// and the maximum possible lower bound
let iter = 0..;

assert_eq!((usize::MAX, None), iter.size_hint());

pub fn count(self) -> usize

Consumes the iterator, counting the number of iterations and returning it.

This method will call next repeatedly until None is encountered, returning the number of times it saw Some. Note that next has to be called at least once even if the iterator does not have any elements.

Overflow Behavior

The method does no guarding against overflows, so counting elements of an iterator with more than usize::MAX elements either produces the wrong result or panics. If debug assertions are enabled, a panic is guaranteed.

Panics

This function might panic if the iterator has more than usize::MAX elements.

Examples

Basic usage:

let a = [1, 2, 3];
assert_eq!(a.iter().count(), 3);

let a = [1, 2, 3, 4, 5];
assert_eq!(a.iter().count(), 5);

pub fn last(self) -> Option<Self::Item>

Consumes the iterator, returning the last element.

This method will evaluate the iterator until it returns None. While doing so, it keeps track of the current element. After None is returned, last() will then return the last element it saw.

Examples

Basic usage:

let a = [1, 2, 3];
assert_eq!(a.iter().last(), Some(&3));

let a = [1, 2, 3, 4, 5];
assert_eq!(a.iter().last(), Some(&5));

pub fn advance_by(&mut self, n: usize) -> Result<(), usize>

🔬 This is a nightly-only experimental API. (iter_advance_by)

recently added

Advances the iterator by n elements.

This method will eagerly skip n elements by calling next up to n times until None is encountered.

advance_by(n) will return Ok(()) if the iterator successfully advances by n elements, or Err(k) if None is encountered, where k is the number of elements the iterator is advanced by before running out of elements (i.e. the length of the iterator). Note that k is always less than n.

Calling advance_by(0) does not consume any elements and always returns Ok(()).

Examples

Basic usage:

#![feature(iter_advance_by)]

let a = [1, 2, 3, 4];
let mut iter = a.iter();

assert_eq!(iter.advance_by(2), Ok(()));
assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.advance_by(0), Ok(()));
assert_eq!(iter.advance_by(100), Err(1)); // only `&4` was skipped

pub fn nth(&mut self, n: usize) -> Option<Self::Item>

Returns the nth element of the iterator.

Like most indexing operations, the count starts from zero, so nth(0) returns the first value, nth(1) the second, and so on.

Note that all preceding elements, as well as the returned element, will be consumed from the iterator. That means that the preceding elements will be discarded, and also that calling nth(0) multiple times on the same iterator will return different elements.

nth() will return None if n is greater than or equal to the length of the iterator.

Examples

Basic usage:

let a = [1, 2, 3];
assert_eq!(a.iter().nth(1), Some(&2));

Calling nth() multiple times doesn't rewind the iterator:

let a = [1, 2, 3];

let mut iter = a.iter();

assert_eq!(iter.nth(1), Some(&2));
assert_eq!(iter.nth(1), None);

Returning None if there are less than n + 1 elements:

let a = [1, 2, 3];
assert_eq!(a.iter().nth(10), None);

pub fn step_by(self, step: usize) -> StepBy<Self>

Creates an iterator starting at the same point, but stepping by the given amount at each iteration.

Note 1: The first element of the iterator will always be returned, regardless of the step given.

Note 2: The time at which ignored elements are pulled is not fixed. StepBy behaves like the sequence next(), nth(step-1), nth(step-1), …, but is also free to behave like the sequence advance_n_and_return_first(step), advance_n_and_return_first(step), … Which way is used may change for some iterators for performance reasons. The second way will advance the iterator earlier and may consume more items.

advance_n_and_return_first is the equivalent of:

fn advance_n_and_return_first<I>(iter: &mut I, total_step: usize) -> Option<I::Item>
where
    I: Iterator,
{
    let next = iter.next();
    if total_step > 1 {
        iter.nth(total_step-2);
    }
    next
}

Panics

The method will panic if the given step is 0.

Examples

Basic usage:

let a = [0, 1, 2, 3, 4, 5];
let mut iter = a.iter().step_by(2);

assert_eq!(iter.next(), Some(&0));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), Some(&4));
assert_eq!(iter.next(), None);

pub fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator<Item = Self::Item>, 

Takes two iterators and creates a new iterator over both in sequence.

chain() will return a new iterator which will first iterate over values from the first iterator and then over values from the second iterator.

In other words, it links two iterators together, in a chain. 🔗

once is commonly used to adapt a single value into a chain of other kinds of iteration.

Examples

Basic usage:

let a1 = [1, 2, 3];
let a2 = [4, 5, 6];

let mut iter = a1.iter().chain(a2.iter());

assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.next(), Some(&4));
assert_eq!(iter.next(), Some(&5));
assert_eq!(iter.next(), Some(&6));
assert_eq!(iter.next(), None);

Since the argument to chain() uses IntoIterator, we can pass anything that can be converted into an Iterator, not just an Iterator itself. For example, slices (&[T]) implement IntoIterator, and so can be passed to chain() directly:

let s1 = &[1, 2, 3];
let s2 = &[4, 5, 6];

let mut iter = s1.iter().chain(s2);

assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.next(), Some(&4));
assert_eq!(iter.next(), Some(&5));
assert_eq!(iter.next(), Some(&6));
assert_eq!(iter.next(), None);

If you work with Windows API, you may wish to convert OsStr to Vec<u16>:

#[cfg(windows)]
fn os_str_to_utf16(s: &std::ffi::OsStr) -> Vec<u16> {
    use std::os::windows::ffi::OsStrExt;
    s.encode_wide().chain(std::iter::once(0)).collect()
}

pub fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator, 

'Zips up' two iterators into a single iterator of pairs.

zip() returns a new iterator that will iterate over two other iterators, returning a tuple where the first element comes from the first iterator, and the second element comes from the second iterator.

In other words, it zips two iterators together, into a single one.

If either iterator returns None, next from the zipped iterator will return None. If the first iterator returns None, zip will short-circuit and next will not be called on the second iterator.

Examples

Basic usage:

let a1 = [1, 2, 3];
let a2 = [4, 5, 6];

let mut iter = a1.iter().zip(a2.iter());

assert_eq!(iter.next(), Some((&1, &4)));
assert_eq!(iter.next(), Some((&2, &5)));
assert_eq!(iter.next(), Some((&3, &6)));
assert_eq!(iter.next(), None);

Since the argument to zip() uses IntoIterator, we can pass anything that can be converted into an Iterator, not just an Iterator itself. For example, slices (&[T]) implement IntoIterator, and so can be passed to zip() directly:

let s1 = &[1, 2, 3];
let s2 = &[4, 5, 6];

let mut iter = s1.iter().zip(s2);

assert_eq!(iter.next(), Some((&1, &4)));
assert_eq!(iter.next(), Some((&2, &5)));
assert_eq!(iter.next(), Some((&3, &6)));
assert_eq!(iter.next(), None);

zip() is often used to zip an infinite iterator to a finite one. This works because the finite iterator will eventually return None, ending the zipper. Zipping with (0..) can look a lot like enumerate:

let enumerate: Vec<_> = "foo".chars().enumerate().collect();

let zipper: Vec<_> = (0..).zip("foo".chars()).collect();

assert_eq!((0, 'f'), enumerate[0]);
assert_eq!((0, 'f'), zipper[0]);

assert_eq!((1, 'o'), enumerate[1]);
assert_eq!((1, 'o'), zipper[1]);

assert_eq!((2, 'o'), enumerate[2]);
assert_eq!((2, 'o'), zipper[2]);

pub fn intersperse(self, separator: Self::Item) -> Intersperse<Self> where
    Self::Item: Clone, 

🔬 This is a nightly-only experimental API. (iter_intersperse)

recently added

Creates a new iterator which places a copy of separator between adjacent items of the original iterator.

In case separator does not implement Clone or needs to be computed every time, use intersperse_with.

Examples

Basic usage:

#![feature(iter_intersperse)]

let mut a = [0, 1, 2].iter().intersperse(&100);
assert_eq!(a.next(), Some(&0));   // The first element from `a`.
assert_eq!(a.next(), Some(&100)); // The separator.
assert_eq!(a.next(), Some(&1));   // The next element from `a`.
assert_eq!(a.next(), Some(&100)); // The separator.
assert_eq!(a.next(), Some(&2));   // The last element from `a`.
assert_eq!(a.next(), None);       // The iterator is finished.

intersperse can be very useful to join an iterator's items using a common element:

#![feature(iter_intersperse)]

let hello = ["Hello", "World", "!"].iter().copied().intersperse(" ").collect::<String>();
assert_eq!(hello, "Hello World !");

pub fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> where
    G: FnMut() -> Self::Item, 

🔬 This is a nightly-only experimental API. (iter_intersperse)

recently added

Creates a new iterator which places an item generated by separator between adjacent items of the original iterator.

The closure will be called exactly once each time an item is placed between two adjacent items from the underlying iterator; specifically, the closure is not called if the underlying iterator yields less than two items and after the last item is yielded.

If the iterator's item implements Clone, it may be easier to use intersperse.

Examples

Basic usage:

#![feature(iter_intersperse)]

#[derive(PartialEq, Debug)]
struct NotClone(usize);

let v = vec![NotClone(0), NotClone(1), NotClone(2)];
let mut it = v.into_iter().intersperse_with(|| NotClone(99));

assert_eq!(it.next(), Some(NotClone(0)));  // The first element from `v`.
assert_eq!(it.next(), Some(NotClone(99))); // The separator.
assert_eq!(it.next(), Some(NotClone(1)));  // The next element from `v`.
assert_eq!(it.next(), Some(NotClone(99))); // The separator.
assert_eq!(it.next(), Some(NotClone(2)));  // The last element from from `v`.
assert_eq!(it.next(), None);               // The iterator is finished.

intersperse_with can be used in situations where the separator needs to be computed:

#![feature(iter_intersperse)]

let src = ["Hello", "to", "all", "people", "!!"].iter().copied();

// The closure mutably borrows its context to generate an item.
let mut happy_emojis = [" ❤️ ", " 😀 "].iter().copied();
let separator = || happy_emojis.next().unwrap_or(" 🦀 ");

let result = src.intersperse_with(separator).collect::<String>();
assert_eq!(result, "Hello ❤️ to 😀 all 🦀 people 🦀 !!");

pub fn map<B, F>(self, f: F) -> Map<Self, F> where
    F: FnMut(Self::Item) -> B, 

Takes a closure and creates an iterator which calls that closure on each element.

map() transforms one iterator into another, by means of its argument: something that implements FnMut. It produces a new iterator which calls this closure on each element of the original iterator.

If you are good at thinking in types, you can think of map() like this: If you have an iterator that gives you elements of some type A, and you want an iterator of some other type B, you can use map(), passing a closure that takes an A and returns a B.

map() is conceptually similar to a for loop. However, as map() is lazy, it is best used when you're already working with other iterators. If you're doing some sort of looping for a side effect, it's considered more idiomatic to use for than map().

Examples

Basic usage:

let a = [1, 2, 3];

let mut iter = a.iter().map(|x| 2 * x);

assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), Some(4));
assert_eq!(iter.next(), Some(6));
assert_eq!(iter.next(), None);

If you're doing some sort of side effect, prefer for to map():

// don't do this:
(0..5).map(|x| println!("{}", x));

// it won't even execute, as it is lazy. Rust will warn you about this.

// Instead, use for:
for x in 0..5 {
    println!("{}", x);
}

pub fn for_each<F>(self, f: F) where
    F: FnMut(Self::Item), 

Calls a closure on each element of an iterator.

This is equivalent to using a for loop on the iterator, although break and continue are not possible from a closure. It's generally more idiomatic to use a for loop, but for_each may be more legible when processing items at the end of longer iterator chains. In some cases for_each may also be faster than a loop, because it will use internal iteration on adaptors like Chain.

Examples

Basic usage:

use std::sync::mpsc::channel;

let (tx, rx) = channel();
(0..5).map(|x| x * 2 + 1)
      .for_each(move |x| tx.send(x).unwrap());

let v: Vec<_> =  rx.iter().collect();
assert_eq!(v, vec![1, 3, 5, 7, 9]);

For such a small example, a for loop may be cleaner, but for_each might be preferable to keep a functional style with longer iterators:

(0..5).flat_map(|x| x * 100 .. x * 110)
      .enumerate()
      .filter(|&(i, x)| (i + x) % 3 == 0)
      .for_each(|(i, x)| println!("{}:{}", i, x));

pub fn filter<P>(self, predicate: P) -> Filter<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator which uses a closure to determine if an element should be yielded.

Given an element the closure must return true or false. The returned iterator will yield only the elements for which the closure returns true.

Examples

Basic usage:

let a = [0i32, 1, 2];

let mut iter = a.iter().filter(|x| x.is_positive());

assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), None);

Because the closure passed to filter() takes a reference, and many iterators iterate over references, this leads to a possibly confusing situation, where the type of the closure is a double reference:

let a = [0, 1, 2];

let mut iter = a.iter().filter(|x| **x > 1); // need two *s!

assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), None);

It's common to instead use destructuring on the argument to strip away one:

let a = [0, 1, 2];

let mut iter = a.iter().filter(|&x| *x > 1); // both & and *

assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), None);

or both:

let a = [0, 1, 2];

let mut iter = a.iter().filter(|&&x| x > 1); // two &s

assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), None);

of these layers.

Note that iter.filter(f).next() is equivalent to iter.find(f).

pub fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
    F: FnMut(Self::Item) -> Option<B>, 

Creates an iterator that both filters and maps.

The returned iterator yields only the values for which the supplied closure returns Some(value).

filter_map can be used to make chains of filter and map more concise. The example below shows how a map().filter().map() can be shortened to a single call to filter_map.

Examples

Basic usage:

let a = ["1", "two", "NaN", "four", "5"];

let mut iter = a.iter().filter_map(|s| s.parse().ok());

assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), Some(5));
assert_eq!(iter.next(), None);

Here's the same example, but with filter and map:

let a = ["1", "two", "NaN", "four", "5"];
let mut iter = a.iter().map(|s| s.parse()).filter(|s| s.is_ok()).map(|s| s.unwrap());
assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), Some(5));
assert_eq!(iter.next(), None);

pub fn enumerate(self) -> Enumerate<Self>

Creates an iterator which gives the current iteration count as well as the next value.

The iterator returned yields pairs (i, val), where i is the current index of iteration and val is the value returned by the iterator.

enumerate() keeps its count as a usize. If you want to count by a different sized integer, the zip function provides similar functionality.

Overflow Behavior

The method does no guarding against overflows, so enumerating more than usize::MAX elements either produces the wrong result or panics. If debug assertions are enabled, a panic is guaranteed.

Panics

The returned iterator might panic if the to-be-returned index would overflow a usize.

Examples

let a = ['a', 'b', 'c'];

let mut iter = a.iter().enumerate();

assert_eq!(iter.next(), Some((0, &'a')));
assert_eq!(iter.next(), Some((1, &'b')));
assert_eq!(iter.next(), Some((2, &'c')));
assert_eq!(iter.next(), None);

pub fn peekable(self) -> Peekable<Self>

Creates an iterator which can use peek to look at the next element of the iterator without consuming it.

Adds a peek method to an iterator. See its documentation for more information.

Note that the underlying iterator is still advanced when peek is called for the first time: In order to retrieve the next element, next is called on the underlying iterator, hence any side effects (i.e. anything other than fetching the next value) of the next method will occur.

Examples

Basic usage:

let xs = [1, 2, 3];

let mut iter = xs.iter().peekable();

// peek() lets us see into the future
assert_eq!(iter.peek(), Some(&&1));
assert_eq!(iter.next(), Some(&1));

assert_eq!(iter.next(), Some(&2));

// we can peek() multiple times, the iterator won't advance
assert_eq!(iter.peek(), Some(&&3));
assert_eq!(iter.peek(), Some(&&3));

assert_eq!(iter.next(), Some(&3));

// after the iterator is finished, so is peek()
assert_eq!(iter.peek(), None);
assert_eq!(iter.next(), None);

pub fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that skips elements based on a predicate.

skip_while() takes a closure as an argument. It will call this closure on each element of the iterator, and ignore elements until it returns false.

After false is returned, skip_while()'s job is over, and the rest of the elements are yielded.

Examples

Basic usage:

let a = [-1i32, 0, 1];

let mut iter = a.iter().skip_while(|x| x.is_negative());

assert_eq!(iter.next(), Some(&0));
assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), None);

Because the closure passed to skip_while() takes a reference, and many iterators iterate over references, this leads to a possibly confusing situation, where the type of the closure is a double reference:

let a = [-1, 0, 1];

let mut iter = a.iter().skip_while(|x| **x < 0); // need two *s!

assert_eq!(iter.next(), Some(&0));
assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), None);

Stopping after an initial false:

let a = [-1, 0, 1, -2];

let mut iter = a.iter().skip_while(|x| **x < 0);

assert_eq!(iter.next(), Some(&0));
assert_eq!(iter.next(), Some(&1));

// while this would have been false, since we already got a false,
// skip_while() isn't used any more
assert_eq!(iter.next(), Some(&-2));

assert_eq!(iter.next(), None);

pub fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that yields elements based on a predicate.

take_while() takes a closure as an argument. It will call this closure on each element of the iterator, and yield elements while it returns true.

After false is returned, take_while()'s job is over, and the rest of the elements are ignored.

Examples

Basic usage:

let a = [-1i32, 0, 1];

let mut iter = a.iter().take_while(|x| x.is_negative());

assert_eq!(iter.next(), Some(&-1));
assert_eq!(iter.next(), None);

Because the closure passed to take_while() takes a reference, and many iterators iterate over references, this leads to a possibly confusing situation, where the type of the closure is a double reference:

let a = [-1, 0, 1];

let mut iter = a.iter().take_while(|x| **x < 0); // need two *s!

assert_eq!(iter.next(), Some(&-1));
assert_eq!(iter.next(), None);

Stopping after an initial false:

let a = [-1, 0, 1, -2];

let mut iter = a.iter().take_while(|x| **x < 0);

assert_eq!(iter.next(), Some(&-1));

// We have more elements that are less than zero, but since we already
// got a false, take_while() isn't used any more
assert_eq!(iter.next(), None);

Because take_while() needs to look at the value in order to see if it should be included or not, consuming iterators will see that it is removed:

let a = [1, 2, 3, 4];
let mut iter = a.iter();

let result: Vec<i32> = iter.by_ref()
                           .take_while(|n| **n != 3)
                           .cloned()
                           .collect();

assert_eq!(result, &[1, 2]);

let result: Vec<i32> = iter.cloned().collect();

assert_eq!(result, &[4]);

The 3 is no longer there, because it was consumed in order to see if the iteration should stop, but wasn't placed back into the iterator.

pub fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> where
    P: FnMut(Self::Item) -> Option<B>, 

🔬 This is a nightly-only experimental API. (iter_map_while)

recently added

Creates an iterator that both yields elements based on a predicate and maps.

map_while() takes a closure as an argument. It will call this closure on each element of the iterator, and yield elements while it returns Some(_).

Examples

Basic usage:

#![feature(iter_map_while)]
let a = [-1i32, 4, 0, 1];

let mut iter = a.iter().map_while(|x| 16i32.checked_div(*x));

assert_eq!(iter.next(), Some(-16));
assert_eq!(iter.next(), Some(4));
assert_eq!(iter.next(), None);

Here's the same example, but with take_while and map:

let a = [-1i32, 4, 0, 1];

let mut iter = a.iter()
                .map(|x| 16i32.checked_div(*x))
                .take_while(|x| x.is_some())
                .map(|x| x.unwrap());

assert_eq!(iter.next(), Some(-16));
assert_eq!(iter.next(), Some(4));
assert_eq!(iter.next(), None);

Stopping after an initial None:

#![feature(iter_map_while)]
use std::convert::TryFrom;

let a = [0, 1, 2, -3, 4, 5, -6];

let iter = a.iter().map_while(|x| u32::try_from(*x).ok());
let vec = iter.collect::<Vec<_>>();

// We have more elements which could fit in u32 (4, 5), but `map_while` returned `None` for `-3`
// (as the `predicate` returned `None`) and `collect` stops at the first `None` encountered.
assert_eq!(vec, vec![0, 1, 2]);

Because map_while() needs to look at the value in order to see if it should be included or not, consuming iterators will see that it is removed:

#![feature(iter_map_while)]
use std::convert::TryFrom;

let a = [1, 2, -3, 4];
let mut iter = a.iter();

let result: Vec<u32> = iter.by_ref()
                           .map_while(|n| u32::try_from(*n).ok())
                           .collect();

assert_eq!(result, &[1, 2]);

let result: Vec<i32> = iter.cloned().collect();

assert_eq!(result, &[4]);

The -3 is no longer there, because it was consumed in order to see if the iteration should stop, but wasn't placed back into the iterator.

Note that unlike take_while this iterator is not fused. It is also not specified what this iterator returns after the first None is returned. If you need fused iterator, use fuse.

pub fn skip(self, n: usize) -> Skip<Self>

Creates an iterator that skips the first n elements.

After they have been consumed, the rest of the elements are yielded. Rather than overriding this method directly, instead override the nth method.

Examples

Basic usage:

let a = [1, 2, 3];

let mut iter = a.iter().skip(2);

assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.next(), None);

pub fn take(self, n: usize) -> Take<Self>

Creates an iterator that yields its first n elements.

Examples

Basic usage:

let a = [1, 2, 3];

let mut iter = a.iter().take(2);

assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), None);

take() is often used with an infinite iterator, to make it finite:

let mut iter = (0..).take(3);

assert_eq!(iter.next(), Some(0));
assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), None);

If less than n elements are available, take will limit itself to the size of the underlying iterator:

let v = vec![1, 2];
let mut iter = v.into_iter().take(5);
assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), None);

pub fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
    F: FnMut(&mut St, Self::Item) -> Option<B>, 

An iterator adaptor similar to fold that holds internal state and produces a new iterator.

scan() takes two arguments: an initial value which seeds the internal state, and a closure with two arguments, the first being a mutable reference to the internal state and the second an iterator element. The closure can assign to the internal state to share state between iterations.

On iteration, the closure will be applied to each element of the iterator and the return value from the closure, an Option, is yielded by the iterator.

Examples

Basic usage:

let a = [1, 2, 3];

let mut iter = a.iter().scan(1, |state, &x| {
    // each iteration, we'll multiply the state by the element
    *state = *state * x;

    // then, we'll yield the negation of the state
    Some(-*state)
});

assert_eq!(iter.next(), Some(-1));
assert_eq!(iter.next(), Some(-2));
assert_eq!(iter.next(), Some(-6));
assert_eq!(iter.next(), None);

pub fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
    F: FnMut(Self::Item) -> U,
    U: IntoIterator, 

Creates an iterator that works like map, but flattens nested structure.

The map adapter is very useful, but only when the closure argument produces values. If it produces an iterator instead, there's an extra layer of indirection. flat_map() will remove this extra layer on its own.

You can think of flat_map(f) as the semantic equivalent of mapping, and then flattening as in map(f).flatten().

Another way of thinking about flat_map(): map's closure returns one item for each element, and flat_map()'s closure returns an iterator for each element.

Examples

Basic usage:

let words = ["alpha", "beta", "gamma"];

// chars() returns an iterator
let merged: String = words.iter()
                          .flat_map(|s| s.chars())
                          .collect();
assert_eq!(merged, "alphabetagamma");

pub fn flatten(self) -> Flatten<Self> where
    Self::Item: IntoIterator, 

Creates an iterator that flattens nested structure.

This is useful when you have an iterator of iterators or an iterator of things that can be turned into iterators and you want to remove one level of indirection.

Examples

Basic usage:

let data = vec![vec![1, 2, 3, 4], vec![5, 6]];
let flattened = data.into_iter().flatten().collect::<Vec<u8>>();
assert_eq!(flattened, &[1, 2, 3, 4, 5, 6]);

Mapping and then flattening:

let words = ["alpha", "beta", "gamma"];

// chars() returns an iterator
let merged: String = words.iter()
                          .map(|s| s.chars())
                          .flatten()
                          .collect();
assert_eq!(merged, "alphabetagamma");

You can also rewrite this in terms of flat_map(), which is preferable in this case since it conveys intent more clearly:

let words = ["alpha", "beta", "gamma"];

// chars() returns an iterator
let merged: String = words.iter()
                          .flat_map(|s| s.chars())
                          .collect();
assert_eq!(merged, "alphabetagamma");

Flattening only removes one level of nesting at a time:

let d3 = [[[1, 2], [3, 4]], [[5, 6], [7, 8]]];

let d2 = d3.iter().flatten().collect::<Vec<_>>();
assert_eq!(d2, [&[1, 2], &[3, 4], &[5, 6], &[7, 8]]);

let d1 = d3.iter().flatten().flatten().collect::<Vec<_>>();
assert_eq!(d1, [&1, &2, &3, &4, &5, &6, &7, &8]);

Here we see that flatten() does not perform a "deep" flatten. Instead, only one level of nesting is removed. That is, if you flatten() a three-dimensional array, the result will be two-dimensional and not one-dimensional. To get a one-dimensional structure, you have to flatten() again.

pub fn fuse(self) -> Fuse<Self>

Creates an iterator which ends after the first None.

After an iterator returns None, future calls may or may not yield Some(T) again. fuse() adapts an iterator, ensuring that after a None is given, it will always return None forever.

Examples

Basic usage:

// an iterator which alternates between Some and None
struct Alternate {
    state: i32,
}

impl Iterator for Alternate {
    type Item = i32;

    fn next(&mut self) -> Option<i32> {
        let val = self.state;
        self.state = self.state + 1;

        // if it's even, Some(i32), else None
        if val % 2 == 0 {
            Some(val)
        } else {
            None
        }
    }
}

let mut iter = Alternate { state: 0 };

// we can see our iterator going back and forth
assert_eq!(iter.next(), Some(0));
assert_eq!(iter.next(), None);
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), None);

// however, once we fuse it...
let mut iter = iter.fuse();

assert_eq!(iter.next(), Some(4));
assert_eq!(iter.next(), None);

// it will always return `None` after the first time.
assert_eq!(iter.next(), None);
assert_eq!(iter.next(), None);
assert_eq!(iter.next(), None);

pub fn inspect<F>(self, f: F) -> Inspect<Self, F> where
    F: FnMut(&Self::Item), 

Does something with each element of an iterator, passing the value on.

When using iterators, you'll often chain several of them together. While working on such code, you might want to check out what's happening at various parts in the pipeline. To do that, insert a call to inspect().

It's more common for inspect() to be used as a debugging tool than to exist in your final code, but applications may find it useful in certain situations when errors need to be logged before being discarded.

Examples

Basic usage:

let a = [1, 4, 2, 3];

// this iterator sequence is complex.
let sum = a.iter()
    .cloned()
    .filter(|x| x % 2 == 0)
    .fold(0, |sum, i| sum + i);

println!("{}", sum);

// let's add some inspect() calls to investigate what's happening
let sum = a.iter()
    .cloned()
    .inspect(|x| println!("about to filter: {}", x))
    .filter(|x| x % 2 == 0)
    .inspect(|x| println!("made it through filter: {}", x))
    .fold(0, |sum, i| sum + i);

println!("{}", sum);

This will print:

6
about to filter: 1
about to filter: 4
made it through filter: 4
about to filter: 2
made it through filter: 2
about to filter: 3
6

Logging errors before discarding them:

let lines = ["1", "2", "a"];

let sum: i32 = lines
    .iter()
    .map(|line| line.parse::<i32>())
    .inspect(|num| {
        if let Err(ref e) = *num {
            println!("Parsing error: {}", e);
        }
    })
    .filter_map(Result::ok)
    .sum();

println!("Sum: {}", sum);

This will print:

Parsing error: invalid digit found in string
Sum: 3

pub fn by_ref(&mut self) -> &mut Self

Borrows an iterator, rather than consuming it.

This is useful to allow applying iterator adaptors while still retaining ownership of the original iterator.

Examples

Basic usage:

let a = [1, 2, 3];

let iter = a.iter();

let sum: i32 = iter.take(5).fold(0, |acc, i| acc + i);

assert_eq!(sum, 6);

// if we try to use iter again, it won't work. The following line
// gives "error: use of moved value: `iter`
// assert_eq!(iter.next(), None);

// let's try that again
let a = [1, 2, 3];

let mut iter = a.iter();

// instead, we add in a .by_ref()
let sum: i32 = iter.by_ref().take(2).fold(0, |acc, i| acc + i);

assert_eq!(sum, 3);

// now this is just fine:
assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.next(), None);

#[must_use = "if you really need to exhaust the iterator, consider `.for_each(drop)` instead"]pub fn collect<B>(self) -> B where
    B: FromIterator<Self::Item>, 

Transforms an iterator into a collection.

collect() can take anything iterable, and turn it into a relevant collection. This is one of the more powerful methods in the standard library, used in a variety of contexts.

The most basic pattern in which collect() is used is to turn one collection into another. You take a collection, call iter on it, do a bunch of transformations, and then collect() at the end.

collect() can also create instances of types that are not typical collections. For example, a String can be built from chars, and an iterator of Result<T, E> items can be collected into Result<Collection<T>, E>. See the examples below for more.

Because collect() is so general, it can cause problems with type inference. As such, collect() is one of the few times you'll see the syntax affectionately known as the 'turbofish': ::<>. This helps the inference algorithm understand specifically which collection you're trying to collect into.

Examples

Basic usage:

let a = [1, 2, 3];

let doubled: Vec<i32> = a.iter()
                         .map(|&x| x * 2)
                         .collect();

assert_eq!(vec![2, 4, 6], doubled);

Note that we needed the : Vec<i32> on the left-hand side. This is because we could collect into, for example, a VecDeque<T> instead:

use std::collections::VecDeque;

let a = [1, 2, 3];

let doubled: VecDeque<i32> = a.iter().map(|&x| x * 2).collect();

assert_eq!(2, doubled[0]);
assert_eq!(4, doubled[1]);
assert_eq!(6, doubled[2]);

Using the 'turbofish' instead of annotating doubled:

let a = [1, 2, 3];

let doubled = a.iter().map(|x| x * 2).collect::<Vec<i32>>();

assert_eq!(vec![2, 4, 6], doubled);

Because collect() only cares about what you're collecting into, you can still use a partial type hint, _, with the turbofish:

let a = [1, 2, 3];

let doubled = a.iter().map(|x| x * 2).collect::<Vec<_>>();

assert_eq!(vec![2, 4, 6], doubled);

Using collect() to make a String:

let chars = ['g', 'd', 'k', 'k', 'n'];

let hello: String = chars.iter()
    .map(|&x| x as u8)
    .map(|x| (x + 1) as char)
    .collect();

assert_eq!("hello", hello);

If you have a list of Result<T, E>s, you can use collect() to see if any of them failed:

let results = [Ok(1), Err("nope"), Ok(3), Err("bad")];

let result: Result<Vec<_>, &str> = results.iter().cloned().collect();

// gives us the first error
assert_eq!(Err("nope"), result);

let results = [Ok(1), Ok(3)];

let result: Result<Vec<_>, &str> = results.iter().cloned().collect();

// gives us the list of answers
assert_eq!(Ok(vec![1, 3]), result);

pub fn partition<B, F>(self, f: F) -> (B, B) where
    F: FnMut(&Self::Item) -> bool,
    B: Default + Extend<Self::Item>, 

Consumes an iterator, creating two collections from it.

The predicate passed to partition() can return true, or false. partition() returns a pair, all of the elements for which it returned true, and all of the elements for which it returned false.

See also is_partitioned() and partition_in_place().

Examples

Basic usage:

let a = [1, 2, 3];

let (even, odd): (Vec<i32>, Vec<i32>) = a
    .iter()
    .partition(|&n| n % 2 == 0);

assert_eq!(even, vec![2]);
assert_eq!(odd, vec![1, 3]);

pub fn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
    Self: DoubleEndedIterator<Item = &'a mut T>,
    T: 'a,
    P: FnMut(&T) -> bool, 

🔬 This is a nightly-only experimental API. (iter_partition_in_place)

new API

Reorders the elements of this iterator in-place according to the given predicate, such that all those that return true precede all those that return false. Returns the number of true elements found.

The relative order of partitioned items is not maintained.

See also is_partitioned() and partition().

Examples

#![feature(iter_partition_in_place)]

let mut a = [1, 2, 3, 4, 5, 6, 7];

// Partition in-place between evens and odds
let i = a.iter_mut().partition_in_place(|&n| n % 2 == 0);

assert_eq!(i, 3);
assert!(a[..i].iter().all(|&n| n % 2 == 0)); // evens
assert!(a[i..].iter().all(|&n| n % 2 == 1)); // odds

pub fn is_partitioned<P>(self, predicate: P) -> bool where
    P: FnMut(Self::Item) -> bool, 

🔬 This is a nightly-only experimental API. (iter_is_partitioned)

new API

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false.

See also partition() and partition_in_place().

Examples

#![feature(iter_is_partitioned)]

assert!("Iterator".chars().is_partitioned(char::is_uppercase));
assert!(!"IntoIterator".chars().is_partitioned(char::is_uppercase));

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, Self::Item) -> R, 

An iterator method that applies a function as long as it returns successfully, producing a single, final value.

try_fold() takes two arguments: an initial value, and a closure with two arguments: an 'accumulator', and an element. The closure either returns successfully, with the value that the accumulator should have for the next iteration, or it returns failure, with an error value that is propagated back to the caller immediately (short-circuiting).

The initial value is the value the accumulator will have on the first call. If applying the closure succeeded against every element of the iterator, try_fold() returns the final accumulator as success.

Folding is useful whenever you have a collection of something, and want to produce a single value from it.

Note to Implementors

Several of the other (forward) methods have default implementations in terms of this one, so try to implement this explicitly if it can do something better than the default for loop implementation.

In particular, try to have this call try_fold() on the internal parts from which this iterator is composed. If multiple calls are needed, the ? operator may be convenient for chaining the accumulator value along, but beware any invariants that need to be upheld before those early returns. This is a &mut self method, so iteration needs to be resumable after hitting an error here.

Examples

Basic usage:

let a = [1, 2, 3];

// the checked sum of all of the elements of the array
let sum = a.iter().try_fold(0i8, |acc, &x| acc.checked_add(x));

assert_eq!(sum, Some(6));

Short-circuiting:

let a = [10, 20, 30, 100, 40, 50];
let mut it = a.iter();

// This sum overflows when adding the 100 element
let sum = it.try_fold(0i8, |acc, &x| acc.checked_add(x));
assert_eq!(sum, None);

// Because it short-circuited, the remaining elements are still
// available through the iterator.
assert_eq!(it.len(), 2);
assert_eq!(it.next(), Some(&40));

pub fn try_for_each<F, R>(&mut self, f: F) -> R where
    R: Try<Ok = ()>,
    F: FnMut(Self::Item) -> R, 

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error.

This can also be thought of as the fallible form of for_each() or as the stateless version of try_fold().

Examples

use std::fs::rename;
use std::io::{stdout, Write};
use std::path::Path;

let data = ["no_tea.txt", "stale_bread.json", "torrential_rain.png"];

let res = data.iter().try_for_each(|x| writeln!(stdout(), "{}", x));
assert!(res.is_ok());

let mut it = data.iter().cloned();
let res = it.try_for_each(|x| rename(x, Path::new(x).with_extension("old")));
assert!(res.is_err());
// It short-circuited, so the remaining items are still in the iterator:
assert_eq!(it.next(), Some("stale_bread.json"));

pub fn fold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, Self::Item) -> B, 

An iterator method that applies a function, producing a single, final value.

fold() takes two arguments: an initial value, and a closure with two arguments: an 'accumulator', and an element. The closure returns the value that the accumulator should have for the next iteration.

The initial value is the value the accumulator will have on the first call.

After applying this closure to every element of the iterator, fold() returns the accumulator.

This operation is sometimes called 'reduce' or 'inject'.

Folding is useful whenever you have a collection of something, and want to produce a single value from it.

Note: fold(), and similar methods that traverse the entire iterator, may not terminate for infinite iterators, even on traits for which a result is determinable in finite time.

Note to Implementors

Several of the other (forward) methods have default implementations in terms of this one, so try to implement this explicitly if it can do something better than the default for loop implementation.

In particular, try to have this call fold() on the internal parts from which this iterator is composed.

Examples

Basic usage:

let a = [1, 2, 3];

// the sum of all of the elements of the array
let sum = a.iter().fold(0, |acc, x| acc + x);

assert_eq!(sum, 6);

Let's walk through each step of the iteration here:

element	acc	x	result
	0
1	0	1	1
2	1	2	3
3	3	3	6

And so, our final result, 6.

It's common for people who haven't used iterators a lot to use a for loop with a list of things to build up a result. Those can be turned into fold()s:

let numbers = [1, 2, 3, 4, 5];

let mut result = 0;

// for loop:
for i in &numbers {
    result = result + i;
}

// fold:
let result2 = numbers.iter().fold(0, |acc, &x| acc + x);

// they're the same
assert_eq!(result, result2);

pub fn fold_first<F>(self, f: F) -> Option<Self::Item> where
    F: FnMut(Self::Item, Self::Item) -> Self::Item, 

🔬 This is a nightly-only experimental API. (iterator_fold_self)

The same as fold(), but uses the first element in the iterator as the initial value, folding every subsequent element into it. If the iterator is empty, return None; otherwise, return the result of the fold.

Example

Find the maximum value:

#![feature(iterator_fold_self)]

fn find_max<I>(iter: I) -> Option<I::Item>
    where I: Iterator,
          I::Item: Ord,
{
    iter.fold_first(|a, b| {
        if a >= b { a } else { b }
    })
}
let a = [10, 20, 5, -23, 0];
let b: [u32; 0] = [];

assert_eq!(find_max(a.iter()), Some(&20));
assert_eq!(find_max(b.iter()), None);

pub fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if every element of the iterator matches a predicate.

all() takes a closure that returns true or false. It applies this closure to each element of the iterator, and if they all return true, then so does all(). If any of them return false, it returns false.

all() is short-circuiting; in other words, it will stop processing as soon as it finds a false, given that no matter what else happens, the result will also be false.

An empty iterator returns true.

Examples

Basic usage:

let a = [1, 2, 3];

assert!(a.iter().all(|&x| x > 0));

assert!(!a.iter().all(|&x| x > 2));

Stopping at the first false:

let a = [1, 2, 3];

let mut iter = a.iter();

assert!(!iter.all(|&x| x != 2));

// we can still use `iter`, as there are more elements.
assert_eq!(iter.next(), Some(&3));

pub fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if any element of the iterator matches a predicate.

any() takes a closure that returns true or false. It applies this closure to each element of the iterator, and if any of them return true, then so does any(). If they all return false, it returns false.

any() is short-circuiting; in other words, it will stop processing as soon as it finds a true, given that no matter what else happens, the result will also be true.

An empty iterator returns false.

Examples

Basic usage:

let a = [1, 2, 3];

assert!(a.iter().any(|&x| x > 0));

assert!(!a.iter().any(|&x| x > 5));

Stopping at the first true:

let a = [1, 2, 3];

let mut iter = a.iter();

assert!(iter.any(|&x| x != 2));

// we can still use `iter`, as there are more elements.
assert_eq!(iter.next(), Some(&2));

pub fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
    P: FnMut(&Self::Item) -> bool, 

Searches for an element of an iterator that satisfies a predicate.

find() takes a closure that returns true or false. It applies this closure to each element of the iterator, and if any of them return true, then find() returns Some(element). If they all return false, it returns None.

find() is short-circuiting; in other words, it will stop processing as soon as the closure returns true.

Because find() takes a reference, and many iterators iterate over references, this leads to a possibly confusing situation where the argument is a double reference. You can see this effect in the examples below, with &&x.

Examples

Basic usage:

let a = [1, 2, 3];

assert_eq!(a.iter().find(|&&x| x == 2), Some(&2));

assert_eq!(a.iter().find(|&&x| x == 5), None);

Stopping at the first true:

let a = [1, 2, 3];

let mut iter = a.iter();

assert_eq!(iter.find(|&&x| x == 2), Some(&2));

// we can still use `iter`, as there are more elements.
assert_eq!(iter.next(), Some(&3));

Note that iter.find(f) is equivalent to iter.filter(f).next().

pub fn find_map<B, F>(&mut self, f: F) -> Option<B> where
    F: FnMut(Self::Item) -> Option<B>, 

Applies function to the elements of iterator and returns the first non-none result.

iter.find_map(f) is equivalent to iter.filter_map(f).next().

Examples

let a = ["lol", "NaN", "2", "5"];

let first_number = a.iter().find_map(|s| s.parse().ok());

assert_eq!(first_number, Some(2));

pub fn try_find<F, R>(
    &mut self,
    f: F
) -> Result<Option<Self::Item>, <R as Try>::Error> where
    R: Try<Ok = bool>,
    F: FnMut(&Self::Item) -> R, 

🔬 This is a nightly-only experimental API. (try_find)

new API

Applies function to the elements of iterator and returns the first true result or the first error.

Examples

#![feature(try_find)]

let a = ["1", "2", "lol", "NaN", "5"];

let is_my_num = |s: &str, search: i32| -> Result<bool, std::num::ParseIntError> {
    Ok(s.parse::<i32>()?  == search)
};

let result = a.iter().try_find(|&&s| is_my_num(s, 2));
assert_eq!(result, Ok(Some(&"2")));

let result = a.iter().try_find(|&&s| is_my_num(s, 5));
assert!(result.is_err());

pub fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(Self::Item) -> bool, 

Searches for an element in an iterator, returning its index.

position() takes a closure that returns true or false. It applies this closure to each element of the iterator, and if one of them returns true, then position() returns Some(index). If all of them return false, it returns None.

position() is short-circuiting; in other words, it will stop processing as soon as it finds a true.

Overflow Behavior

The method does no guarding against overflows, so if there are more than usize::MAX non-matching elements, it either produces the wrong result or panics. If debug assertions are enabled, a panic is guaranteed.

Panics

This function might panic if the iterator has more than usize::MAX non-matching elements.

Examples

Basic usage:

let a = [1, 2, 3];

assert_eq!(a.iter().position(|&x| x == 2), Some(1));

assert_eq!(a.iter().position(|&x| x == 5), None);

Stopping at the first true:

let a = [1, 2, 3, 4];

let mut iter = a.iter();

assert_eq!(iter.position(|&x| x >= 2), Some(1));

// we can still use `iter`, as there are more elements.
assert_eq!(iter.next(), Some(&3));

// The returned index depends on iterator state
assert_eq!(iter.position(|&x| x == 4), Some(0));

pub fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
    Self: ExactSizeIterator + DoubleEndedIterator,
    P: FnMut(Self::Item) -> bool, 

Searches for an element in an iterator from the right, returning its index.

rposition() takes a closure that returns true or false. It applies this closure to each element of the iterator, starting from the end, and if one of them returns true, then rposition() returns Some(index). If all of them return false, it returns None.

rposition() is short-circuiting; in other words, it will stop processing as soon as it finds a true.

Examples

Basic usage:

let a = [1, 2, 3];

assert_eq!(a.iter().rposition(|&x| x == 3), Some(2));

assert_eq!(a.iter().rposition(|&x| x == 5), None);

Stopping at the first true:

let a = [1, 2, 3];

let mut iter = a.iter();

assert_eq!(iter.rposition(|&x| x == 2), Some(1));

// we can still use `iter`, as there are more elements.
assert_eq!(iter.next(), Some(&1));

pub fn max(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the maximum element of an iterator.

If several elements are equally maximum, the last element is returned. If the iterator is empty, None is returned.

Examples

Basic usage:

let a = [1, 2, 3];
let b: Vec<u32> = Vec::new();

assert_eq!(a.iter().max(), Some(&3));
assert_eq!(b.iter().max(), None);

pub fn min(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the minimum element of an iterator.

If several elements are equally minimum, the first element is returned. If the iterator is empty, None is returned.

Examples

Basic usage:

let a = [1, 2, 3];
let b: Vec<u32> = Vec::new();

assert_eq!(a.iter().min(), Some(&1));
assert_eq!(b.iter().min(), None);

pub fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item) -> B,
    B: Ord, 

Returns the element that gives the maximum value from the specified function.

If several elements are equally maximum, the last element is returned. If the iterator is empty, None is returned.

Examples

let a = [-3_i32, 0, 1, 5, -10];
assert_eq!(*a.iter().max_by_key(|x| x.abs()).unwrap(), -10);

pub fn max_by<F>(self, compare: F) -> Option<Self::Item> where
    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 last element is returned. If the iterator is empty, None is returned.

Examples

let a = [-3_i32, 0, 1, 5, -10];
assert_eq!(*a.iter().max_by(|x, y| x.cmp(y)).unwrap(), 5);

pub fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item) -> B,
    B: Ord, 

Returns the element that gives the minimum value from the specified function.

If several elements are equally minimum, the first element is returned. If the iterator is empty, None is returned.

Examples

let a = [-3_i32, 0, 1, 5, -10];
assert_eq!(*a.iter().min_by_key(|x| x.abs()).unwrap(), 0);

pub fn min_by<F>(self, compare: F) -> Option<Self::Item> where
    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 iterator is empty, None is returned.

Examples

let a = [-3_i32, 0, 1, 5, -10];
assert_eq!(*a.iter().min_by(|x, y| x.cmp(y)).unwrap(), -10);

pub fn rev(self) -> Rev<Self> where
    Self: DoubleEndedIterator, 

Reverses an iterator's direction.

Usually, iterators iterate from left to right. After using rev(), an iterator will instead iterate from right to left.

This is only possible if the iterator has an end, so rev() only works on DoubleEndedIterators.

Examples

let a = [1, 2, 3];

let mut iter = a.iter().rev();

assert_eq!(iter.next(), Some(&3));
assert_eq!(iter.next(), Some(&2));
assert_eq!(iter.next(), Some(&1));

assert_eq!(iter.next(), None);

pub fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
    Self: Iterator<Item = (A, B)>,
    FromA: Default + Extend<A>,
    FromB: Default + Extend<B>, 

Converts an iterator of pairs into a pair of containers.

unzip() consumes an entire iterator of pairs, producing two collections: one from the left elements of the pairs, and one from the right elements.

This function is, in some sense, the opposite of zip.

Examples

Basic usage:

let a = [(1, 2), (3, 4)];

let (left, right): (Vec<_>, Vec<_>) = a.iter().cloned().unzip();

assert_eq!(left, [1, 3]);
assert_eq!(right, [2, 4]);

pub fn copied<'a, T>(self) -> Copied<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Copy, 

Creates an iterator which copies all of its elements.

This is useful when you have an iterator over &T, but you need an iterator over T.

Examples

Basic usage:

let a = [1, 2, 3];

let v_copied: Vec<_> = a.iter().copied().collect();

// copied is the same as .map(|&x| x)
let v_map: Vec<_> = a.iter().map(|&x| x).collect();

assert_eq!(v_copied, vec![1, 2, 3]);
assert_eq!(v_map, vec![1, 2, 3]);

pub fn cloned<'a, T>(self) -> Cloned<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Clone, 

Creates an iterator which clones all of its elements.

This is useful when you have an iterator over &T, but you need an iterator over T.

Examples

Basic usage:

let a = [1, 2, 3];

let v_cloned: Vec<_> = a.iter().cloned().collect();

// cloned is the same as .map(|&x| x), for integers
let v_map: Vec<_> = a.iter().map(|&x| x).collect();

assert_eq!(v_cloned, vec![1, 2, 3]);
assert_eq!(v_map, vec![1, 2, 3]);

pub fn cycle(self) -> Cycle<Self> where
    Self: Clone, 

Repeats an iterator endlessly.

Instead of stopping at None, the iterator will instead start again, from the beginning. After iterating again, it will start at the beginning again. And again. And again. Forever.

Examples

Basic usage:

let a = [1, 2, 3];

let mut it = a.iter().cycle();

assert_eq!(it.next(), Some(&1));
assert_eq!(it.next(), Some(&2));
assert_eq!(it.next(), Some(&3));
assert_eq!(it.next(), Some(&1));
assert_eq!(it.next(), Some(&2));
assert_eq!(it.next(), Some(&3));
assert_eq!(it.next(), Some(&1));

pub fn sum<S>(self) -> S where
    S: Sum<Self::Item>, 

Sums the elements of an iterator.

Takes each element, adds them together, and returns the result.

An empty iterator returns the zero value of the type.

Panics

When calling sum() and a primitive integer type is being returned, this method will panic if the computation overflows and debug assertions are enabled.

Examples

Basic usage:

let a = [1, 2, 3];
let sum: i32 = a.iter().sum();

assert_eq!(sum, 6);

pub fn product<P>(self) -> P where
    P: Product<Self::Item>, 

Iterates over the entire iterator, multiplying all the elements

An empty iterator returns the one value of the type.

Panics

When calling product() and a primitive integer type is being returned, method will panic if the computation overflows and debug assertions are enabled.

Examples

fn factorial(n: u32) -> u32 {
    (1..=n).product()
}
assert_eq!(factorial(0), 1);
assert_eq!(factorial(1), 1);
assert_eq!(factorial(5), 120);

pub fn cmp<I>(self, other: I) -> Ordering where
    I: IntoIterator<Item = Self::Item>,
    Self::Item: Ord, 

Lexicographically compares the elements of this Iterator with those of another.

Examples

use std::cmp::Ordering;

assert_eq!([1].iter().cmp([1].iter()), Ordering::Equal);
assert_eq!([1].iter().cmp([1, 2].iter()), Ordering::Less);
assert_eq!([1, 2].iter().cmp([1].iter()), Ordering::Greater);

pub fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
    F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
    I: IntoIterator, 

🔬 This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

Examples

Basic usage:

#![feature(iter_order_by)]

use std::cmp::Ordering;

let xs = [1, 2, 3, 4];
let ys = [1, 4, 9, 16];

assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| x.cmp(&y)), Ordering::Less);
assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| (x * x).cmp(&y)), Ordering::Equal);
assert_eq!(xs.iter().cmp_by(&ys, |&x, &y| (2 * x).cmp(&y)), Ordering::Greater);

pub fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Lexicographically compares the elements of this Iterator with those of another.

Examples

use std::cmp::Ordering;

assert_eq!([1.].iter().partial_cmp([1.].iter()), Some(Ordering::Equal));
assert_eq!([1.].iter().partial_cmp([1., 2.].iter()), Some(Ordering::Less));
assert_eq!([1., 2.].iter().partial_cmp([1.].iter()), Some(Ordering::Greater));

assert_eq!([f64::NAN].iter().partial_cmp([1.].iter()), None);

pub fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
    F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
    I: IntoIterator, 

🔬 This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

Examples

Basic usage:

#![feature(iter_order_by)]

use std::cmp::Ordering;

let xs = [1.0, 2.0, 3.0, 4.0];
let ys = [1.0, 4.0, 9.0, 16.0];

assert_eq!(
    xs.iter().partial_cmp_by(&ys, |&x, &y| x.partial_cmp(&y)),
    Some(Ordering::Less)
);
assert_eq!(
    xs.iter().partial_cmp_by(&ys, |&x, &y| (x * x).partial_cmp(&y)),
    Some(Ordering::Equal)
);
assert_eq!(
    xs.iter().partial_cmp_by(&ys, |&x, &y| (2.0 * x).partial_cmp(&y)),
    Some(Ordering::Greater)
);

pub fn eq<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are equal to those of another.

Examples

assert_eq!([1].iter().eq([1].iter()), true);
assert_eq!([1].iter().eq([1, 2].iter()), false);

pub fn eq_by<I, F>(self, other: I, eq: F) -> bool where
    F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
    I: IntoIterator, 

🔬 This is a nightly-only experimental API. (iter_order_by)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function.

Examples

Basic usage:

#![feature(iter_order_by)]

let xs = [1, 2, 3, 4];
let ys = [1, 4, 9, 16];

assert!(xs.iter().eq_by(&ys, |&x, &y| x * x == y));

pub fn ne<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are unequal to those of another.

Examples

assert_eq!([1].iter().ne([1].iter()), false);
assert_eq!([1].iter().ne([1, 2].iter()), true);

pub fn lt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically less than those of another.

Examples

assert_eq!([1].iter().lt([1].iter()), false);
assert_eq!([1].iter().lt([1, 2].iter()), true);
assert_eq!([1, 2].iter().lt([1].iter()), false);
assert_eq!([1, 2].iter().lt([1, 2].iter()), false);

pub fn le<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically less or equal to those of another.

Examples

assert_eq!([1].iter().le([1].iter()), true);
assert_eq!([1].iter().le([1, 2].iter()), true);
assert_eq!([1, 2].iter().le([1].iter()), false);
assert_eq!([1, 2].iter().le([1, 2].iter()), true);

pub fn gt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically greater than those of another.

Examples

assert_eq!([1].iter().gt([1].iter()), false);
assert_eq!([1].iter().gt([1, 2].iter()), false);
assert_eq!([1, 2].iter().gt([1].iter()), true);
assert_eq!([1, 2].iter().gt([1, 2].iter()), false);

pub fn ge<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another.

Examples

assert_eq!([1].iter().ge([1].iter()), true);
assert_eq!([1].iter().ge([1, 2].iter()), false);
assert_eq!([1, 2].iter().ge([1].iter()), true);
assert_eq!([1, 2].iter().ge([1, 2].iter()), true);

pub fn is_sorted(self) -> bool where
    Self::Item: PartialOrd<Self::Item>, 

🔬 This is a nightly-only experimental API. (is_sorted)

new API

Checks if the elements of this iterator are sorted.

That is, for each element a and its following element b, a <= b must hold. If the iterator yields exactly zero or one element, true is returned.

Note that if Self::Item is only PartialOrd, but not Ord, the above definition implies that this function returns false if any two consecutive items are not comparable.

Examples

#![feature(is_sorted)]

assert!([1, 2, 2, 9].iter().is_sorted());
assert!(![1, 3, 2, 4].iter().is_sorted());
assert!([0].iter().is_sorted());
assert!(std::iter::empty::<i32>().is_sorted());
assert!(![0.0, 1.0, f32::NAN].iter().is_sorted());

pub fn is_sorted_by<F>(self, compare: F) -> bool where
    F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>, 

🔬 This is a nightly-only experimental API. (is_sorted)

new API

Checks if the elements of this iterator are sorted using the given comparator function.

Instead of using PartialOrd::partial_cmp, this function uses the given compare function to determine the ordering of two elements. Apart from that, it's equivalent to is_sorted; see its documentation for more information.

Examples

#![feature(is_sorted)]

assert!([1, 2, 2, 9].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
assert!(![1, 3, 2, 4].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
assert!([0].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
assert!(std::iter::empty::<i32>().is_sorted_by(|a, b| a.partial_cmp(b)));
assert!(![0.0, 1.0, f32::NAN].iter().is_sorted_by(|a, b| a.partial_cmp(b)));

pub fn is_sorted_by_key<F, K>(self, f: F) -> bool where
    K: PartialOrd<K>,
    F: FnMut(Self::Item) -> K, 

🔬 This is a nightly-only experimental API. (is_sorted)

new API

Checks if the elements of this iterator are sorted using the given key extraction function.

Instead of comparing the iterator's elements directly, this function compares the keys of the elements, as determined by f. Apart from that, it's equivalent to is_sorted; see its documentation for more information.

Examples

#![feature(is_sorted)]

assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));

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Implementations on Foreign Types

impl<'a> Iterator for Iter<'a>

type Item = &'a OsStr

pub fn next(&mut self) -> Option<&'a OsStr>

impl Iterator for ArgsOs

type Item = OsString

pub fn next(&mut self) -> Option<OsString>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, K, V> Iterator for Values<'a, K, V>

type Item = &'a V

pub fn next(&mut self) -> Option<&'a V>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, K, V> Iterator for IterMut<'a, K, V>

type Item = (&'a K, &'a mut V)

pub fn next(&mut self) -> Option<(&'a K, &'a mut V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<R> Iterator for Bytes<R> where
    R: Read, 

type Item = Result<u8, Error>

pub fn next(&mut self) -> Option<Result<u8, Error>>

impl<B> Iterator for Lines<B> where
    B: BufRead, 

type Item = Result<String, Error>

pub fn next(&mut self) -> Option<Result<String, Error>>

impl Iterator for VarsOs

type Item = (OsString, OsString)

pub fn next(&mut self) -> Option<(OsString, OsString)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for Args

type Item = String

pub fn next(&mut self) -> Option<String>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<K> Iterator for IntoIter<K>

type Item = K

pub fn next(&mut self) -> Option<K>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, S> Iterator for Difference<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for CommandArgs<'a>

type Item = &'a OsStr

pub fn next(&mut self) -> Option<&'a OsStr>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, K, V, F> Iterator for DrainFilter<'_, K, V, F> where
    F: FnMut(&K, &mut V) -> bool, 

type Item = (K, V)

pub fn next(&mut self) -> Option<(K, V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for ReadDir

type Item = Result<DirEntry, Error>

pub fn next(&mut self) -> Option<Result<DirEntry, Error>>

impl<'a> Iterator for Chain<'a>

type Item = &'a (dyn Error + 'static)

pub fn next(&mut self) -> Option<<Chain<'a> as Iterator>::Item>

impl<'a> Iterator for CommandEnvs<'a>

type Item = (&'a OsStr, Option<&'a OsStr>)

pub fn next(&mut self) -> Option<<CommandEnvs<'a> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, K> Iterator for Iter<'a, K>

type Item = &'a K

pub fn next(&mut self) -> Option<&'a K>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for Ancestors<'a>

type Item = &'a Path

pub fn next(&mut self) -> Option<<Ancestors<'a> as Iterator>::Item>

impl<'_, K, F> Iterator for DrainFilter<'_, K, F> where
    F: FnMut(&K) -> bool, 

type Item = K

pub fn next(&mut self) -> Option<K>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, S> Iterator for Union<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<K, V> Iterator for IntoValues<K, V>

type Item = V

pub fn next(&mut self) -> Option<V>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for SplitPaths<'a>

type Item = PathBuf

pub fn next(&mut self) -> Option<PathBuf>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for Vars

type Item = (String, String)

pub fn next(&mut self) -> Option<(String, String)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<K, V> Iterator for IntoIter<K, V>

type Item = (K, V)

pub fn next(&mut self) -> Option<(K, V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, K, V> Iterator for Drain<'a, K, V>

type Item = (K, V)

pub fn next(&mut self) -> Option<(K, V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for Incoming<'a>

type Item = Result<UnixStream, Error>

pub fn next(&mut self) -> Option<Result<UnixStream, Error>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<B> Iterator for Split<B> where
    B: BufRead, 

type Item = Result<Vec<u8, Global>, Error>

pub fn next(&mut self) -> Option<Result<Vec<u8, Global>, Error>>

impl<'a, K, V> Iterator for ValuesMut<'a, K, V>

type Item = &'a mut V

pub fn next(&mut self) -> Option<&'a mut V>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for ScmRights<'a>

type Item = i32

pub fn next(&mut self) -> Option<i32>

impl<'a, T, S> Iterator for Intersection<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for Incoming<'a>

type Item = Result<TcpStream, Error>

pub fn next(&mut self) -> Option<Result<TcpStream, Error>>

impl<'a> Iterator for Messages<'a>

type Item = Result<AncillaryData<'a>, AncillaryError>

pub fn next(&mut self) -> Option<<Messages<'a> as Iterator>::Item>

impl<'a> Iterator for ScmCredentials<'a>

type Item = SocketCred

pub fn next(&mut self) -> Option<SocketCred>

impl<'a, K, V> Iterator for Iter<'a, K, V>

type Item = (&'a K, &'a V)

pub fn next(&mut self) -> Option<(&'a K, &'a V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for Components<'a>

type Item = Component<'a>

pub fn next(&mut self) -> Option<Component<'a>>

impl<'a, K> Iterator for Drain<'a, K>

type Item = K

pub fn next(&mut self) -> Option<K>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<K, V> Iterator for IntoKeys<K, V>

type Item = K

pub fn next(&mut self) -> Option<K>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, K, V> Iterator for Keys<'a, K, V>

type Item = &'a K

pub fn next(&mut self) -> Option<&'a K>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, S> Iterator for SymmetricDifference<'a, T, S> where
    T: Eq + Hash,
    S: BuildHasher, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for EscapeUnicode

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn last(self) -> Option<char>

impl<'a, A> Iterator for Iter<'a, A>

type Item = &'a A

pub fn next(&mut self) -> Option<&'a A>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for ToUppercase

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for SplitInclusive<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<A> Iterator for IntoIter<A>

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for EscapeDebug

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for SplitInclusiveMut<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<I> Iterator for DecodeUtf16<I> where
    I: Iterator<Item = u16>, 

type Item = Result<char, DecodeUtf16Error>

pub fn next(&mut self) -> Option<Result<char, DecodeUtf16Error>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, A> Iterator for IterMut<'a, A>

type Item = &'a mut A

pub fn next(&mut self) -> Option<&'a mut A>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl Iterator for EscapeDefault

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<char>

pub fn last(self) -> Option<char>

impl Iterator for ToLowercase

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn advance_by(&mut self, n: usize) -> Result<(), usize>

🔬 This is a nightly-only experimental API. (iter_advance_by)

recently added

pub fn nth(&mut self, n: usize) -> Option<<&'_ mut I as Iterator>::Item>

impl<'a> Iterator for Utf8LossyChunksIter<'a>

type Item = Utf8LossyChunk<'a>

pub fn next(&mut self) -> Option<Utf8LossyChunk<'a>>

impl<T, const N: usize> Iterator for IntoIter<T, N>

type Item = T

pub fn next(&mut self) -> Option<<IntoIter<T, N> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn last(self) -> Option<<IntoIter<T, N> as Iterator>::Item>

impl Iterator for EscapeDefault

type Item = u8

pub fn next(&mut self) -> Option<u8>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<u8>

impl<'_> Iterator for Drain<'_>

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<char>

impl<'a, T> Iterator for Iter<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a T>

impl<'a, T> Iterator for Iter<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a T>

impl<T> Iterator for IntoIterSorted<T> where
    T: Ord, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, T> Iterator for DrainSorted<'_, T> where
    T: Ord, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, T> Iterator for Drain<'_, T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T> Iterator for IterMut<'a, T>

type Item = &'a mut T

pub fn next(&mut self) -> Option<&'a mut T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a mut T>

impl<'_, T, F> Iterator for DrainFilter<'_, T, F> where
    F: FnMut(&mut T) -> bool, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for IntoIter<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for IntoIter<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

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Implementors

impl<'_> Iterator for sp_std::str::Bytes<'_>

type Item = u8

pub fn next(&mut self) -> Option<u8>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn last(self) -> Option<<Bytes<'_> as Iterator>::Item>

pub fn nth(&mut self, n: usize) -> Option<<Bytes<'_> as Iterator>::Item>

pub fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(<Bytes<'_> as Iterator>::Item) -> bool, 

pub fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(<Bytes<'_> as Iterator>::Item) -> bool, 

pub fn find<P>(&mut self, predicate: P) -> Option<<Bytes<'_> as Iterator>::Item> where
    P: FnMut(&<Bytes<'_> as Iterator>::Item) -> bool, 

pub fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(<Bytes<'_> as Iterator>::Item) -> bool, 

pub fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(<Bytes<'_> as Iterator>::Item) -> bool, 

pub unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> u8

impl<'_, I, A> Iterator for Splice<'_, I, A> where
    A: Allocator,
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<Splice<'_, I, A> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, K, V, F> Iterator for sp_std::collections::btree_map::DrainFilter<'_, K, V, F> where
    F: FnMut(&K, &mut V) -> bool, 

type Item = (K, V)

pub fn next(&mut self) -> Option<(K, V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, T> Iterator for sp_std::collections::vec_deque::Drain<'_, T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, T, A> Iterator for sp_std::vec::Drain<'_, T, A> where
    A: Allocator, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'_, T, F, A> Iterator for sp_std::vec::DrainFilter<'_, T, F, A> where
    A: Allocator,
    F: FnMut(&mut T) -> bool, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for CharIndices<'a>

type Item = (usize, char)

pub fn next(&mut self) -> Option<(usize, char)>

pub fn count(self) -> usize

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<(usize, char)>

impl<'a> Iterator for Chars<'a>

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn count(self) -> usize

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<char>

impl<'a> Iterator for EncodeUtf16<'a>

type Item = u16

pub fn next(&mut self) -> Option<u16>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for sp_std::str::EscapeDebug<'a>

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <EscapeDebug<'a> as Iterator>::Item) -> R,
    EscapeDebug<'a>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <EscapeDebug<'a> as Iterator>::Item) -> Acc, 

impl<'a> Iterator for sp_std::str::EscapeDefault<'a>

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <EscapeDefault<'a> as Iterator>::Item) -> R,
    EscapeDefault<'a>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <EscapeDefault<'a> as Iterator>::Item) -> Acc, 

impl<'a> Iterator for sp_std::str::EscapeUnicode<'a>

type Item = char

pub fn next(&mut self) -> Option<char>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <EscapeUnicode<'a> as Iterator>::Item) -> R,
    EscapeUnicode<'a>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <EscapeUnicode<'a> as Iterator>::Item) -> Acc, 

impl<'a> Iterator for sp_std::str::Lines<'a>

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a str>

impl<'a> Iterator for LinesAny<'a>

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a> Iterator for SplitAsciiWhitespace<'a>

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a str>

impl<'a> Iterator for SplitWhitespace<'a>

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a str>

impl<'a, '_, T, F> Iterator for sp_std::collections::btree_set::DrainFilter<'_, T, F> where
    F: 'a + FnMut(&T) -> bool, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, I, T> Iterator for Cloned<I> where
    T: 'a + Clone,
    I: Iterator<Item = &'a T>, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, <Cloned<I> as Iterator>::Item) -> R,
    Cloned<I>: Sized, 

pub fn fold<Acc, F>(self, init: Acc, f: F) -> Acc where
    F: FnMut(Acc, <Cloned<I> as Iterator>::Item) -> Acc, 

pub unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T where
    Cloned<I>: TrustedRandomAccess, 

impl<'a, I, T> Iterator for Copied<I> where
    T: 'a + Copy,
    I: Iterator<Item = &'a T>, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, <Copied<I> as Iterator>::Item) -> R,
    Copied<I>: Sized, 

pub fn fold<Acc, F>(self, init: Acc, f: F) -> Acc where
    F: FnMut(Acc, <Copied<I> as Iterator>::Item) -> Acc, 

pub fn nth(&mut self, n: usize) -> Option<T>

pub fn last(self) -> Option<T>

pub fn count(self) -> usize

pub unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T where
    Copied<I>: TrustedRandomAccess, 

impl<'a, K, V> Iterator for sp_std::collections::btree_map::Iter<'a, K, V> where
    K: 'a,
    V: 'a, 

type Item = (&'a K, &'a V)

pub fn next(&mut self) -> Option<(&'a K, &'a V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<(&'a K, &'a V)>

pub fn min(self) -> Option<(&'a K, &'a V)>

pub fn max(self) -> Option<(&'a K, &'a V)>

impl<'a, K, V> Iterator for sp_std::collections::btree_map::IterMut<'a, K, V> where
    K: 'a,
    V: 'a, 

type Item = (&'a K, &'a mut V)

pub fn next(&mut self) -> Option<(&'a K, &'a mut V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<(&'a K, &'a mut V)>

pub fn min(self) -> Option<(&'a K, &'a mut V)>

pub fn max(self) -> Option<(&'a K, &'a mut V)>

impl<'a, K, V> Iterator for sp_std::collections::btree_map::Keys<'a, K, V>

type Item = &'a K

pub fn next(&mut self) -> Option<&'a K>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a K>

pub fn min(self) -> Option<&'a K>

pub fn max(self) -> Option<&'a K>

impl<'a, K, V> Iterator for sp_std::collections::btree_map::Range<'a, K, V>

type Item = (&'a K, &'a V)

pub fn next(&mut self) -> Option<(&'a K, &'a V)>

pub fn last(self) -> Option<(&'a K, &'a V)>

pub fn min(self) -> Option<(&'a K, &'a V)>

pub fn max(self) -> Option<(&'a K, &'a V)>

impl<'a, K, V> Iterator for RangeMut<'a, K, V>

type Item = (&'a K, &'a mut V)

pub fn next(&mut self) -> Option<(&'a K, &'a mut V)>

pub fn last(self) -> Option<(&'a K, &'a mut V)>

pub fn min(self) -> Option<(&'a K, &'a mut V)>

pub fn max(self) -> Option<(&'a K, &'a mut V)>

impl<'a, K, V> Iterator for sp_std::collections::btree_map::Values<'a, K, V>

type Item = &'a V

pub fn next(&mut self) -> Option<&'a V>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a V>

impl<'a, K, V> Iterator for sp_std::collections::btree_map::ValuesMut<'a, K, V>

type Item = &'a mut V

pub fn next(&mut self) -> Option<&'a mut V>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a mut V>

impl<'a, P> Iterator for MatchIndices<'a, P> where
    P: Pattern<'a>, 

type Item = (usize, &'a str)

pub fn next(&mut self) -> Option<(usize, &'a str)>

impl<'a, P> Iterator for Matches<'a, P> where
    P: Pattern<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for RMatchIndices<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 

type Item = (usize, &'a str)

pub fn next(&mut self) -> Option<(usize, &'a str)>

impl<'a, P> Iterator for RMatches<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for sp_std::str::RSplit<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for sp_std::str::RSplitN<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for RSplitTerminator<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for sp_std::str::Split<'a, P> where
    P: Pattern<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for sp_std::str::SplitN<'a, P> where
    P: Pattern<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, P> Iterator for SplitTerminator<'a, P> where
    P: Pattern<'a>, 

type Item = &'a str

pub fn next(&mut self) -> Option<&'a str>

impl<'a, T> Iterator for sp_std::collections::btree_set::Difference<'a, T> where
    T: Ord, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn min(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::btree_set::Intersection<'a, T> where
    T: Ord, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn min(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::btree_set::Iter<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<&'a T>

pub fn min(self) -> Option<&'a T>

pub fn max(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::btree_set::Range<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn last(self) -> Option<&'a T>

pub fn min(self) -> Option<&'a T>

pub fn max(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::btree_set::SymmetricDifference<'a, T> where
    T: Ord, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn min(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::btree_set::Union<'a, T> where
    T: Ord, 

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn min(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::vec_deque::Iter<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn fold<Acc, F>(self, accum: Acc, f: F) -> Acc where
    F: FnMut(Acc, <Iter<'a, T> as Iterator>::Item) -> Acc, 

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, <Iter<'a, T> as Iterator>::Item) -> R,
    Iter<'a, T>: Sized, 

pub fn nth(&mut self, n: usize) -> Option<<Iter<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<&'a T>

impl<'a, T> Iterator for sp_std::collections::vec_deque::IterMut<'a, T>

type Item = &'a mut T

pub fn next(&mut self) -> Option<&'a mut T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn fold<Acc, F>(self, accum: Acc, f: F) -> Acc where
    F: FnMut(Acc, <IterMut<'a, T> as Iterator>::Item) -> Acc, 

pub fn nth(&mut self, n: usize) -> Option<<IterMut<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<&'a mut T>

impl<'a, T> Iterator for sp_std::result::Iter<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T> Iterator for sp_std::result::IterMut<'a, T>

type Item = &'a mut T

pub fn next(&mut self) -> Option<&'a mut T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T> Iterator for Chunks<'a, T>

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<<Chunks<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<<Chunks<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for ChunksExact<'a, T>

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(
    &mut self,
    n: usize
) -> Option<<ChunksExact<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<<ChunksExact<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for ChunksExactMut<'a, T>

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<&'a mut [T]>

pub fn last(self) -> Option<<ChunksExactMut<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for ChunksMut<'a, T>

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<&'a mut [T]>

pub fn last(self) -> Option<<ChunksMut<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for sp_std::slice::Iter<'a, T>

type Item = &'a T

pub fn next(&mut self) -> Option<&'a T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<&'a T>

pub fn last(self) -> Option<&'a T>

pub fn for_each<F>(self, f: F) where
    F: FnMut(<Iter<'a, T> as Iterator>::Item),
    Iter<'a, T>: Sized, 

pub fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(<Iter<'a, T> as Iterator>::Item) -> bool,
    Iter<'a, T>: Sized, 

pub fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(<Iter<'a, T> as Iterator>::Item) -> bool,
    Iter<'a, T>: Sized, 

pub fn find<P>(
    &mut self,
    predicate: P
) -> Option<<Iter<'a, T> as Iterator>::Item> where
    P: FnMut(&<Iter<'a, T> as Iterator>::Item) -> bool,
    Iter<'a, T>: Sized, 

pub fn find_map<B, F>(&mut self, f: F) -> Option<B> where
    F: FnMut(<Iter<'a, T> as Iterator>::Item) -> Option<B>,
    Iter<'a, T>: Sized, 

pub fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(<Iter<'a, T> as Iterator>::Item) -> bool,
    Iter<'a, T>: Sized, 

pub fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(<Iter<'a, T> as Iterator>::Item) -> bool,
    Iter<'a, T>: Sized,
    Iter<'a, T>: ExactSizeIterator,
    Iter<'a, T>: DoubleEndedIterator, 

pub fn is_sorted_by<F>(self, compare: F) -> bool where
    F: FnMut(&<Iter<'a, T> as Iterator>::Item, &<Iter<'a, T> as Iterator>::Item) -> Option<Ordering>,
    Iter<'a, T>: Sized, 

🔬 This is a nightly-only experimental API. (is_sorted)

new API

impl<'a, T> Iterator for sp_std::slice::IterMut<'a, T>

type Item = &'a mut T

pub fn next(&mut self) -> Option<&'a mut T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<&'a mut T>

pub fn last(self) -> Option<&'a mut T>

pub fn for_each<F>(self, f: F) where
    F: FnMut(<IterMut<'a, T> as Iterator>::Item),
    IterMut<'a, T>: Sized, 

pub fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(<IterMut<'a, T> as Iterator>::Item) -> bool,
    IterMut<'a, T>: Sized, 

pub fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(<IterMut<'a, T> as Iterator>::Item) -> bool,
    IterMut<'a, T>: Sized, 

pub fn find<P>(
    &mut self,
    predicate: P
) -> Option<<IterMut<'a, T> as Iterator>::Item> where
    P: FnMut(&<IterMut<'a, T> as Iterator>::Item) -> bool,
    IterMut<'a, T>: Sized, 

pub fn find_map<B, F>(&mut self, f: F) -> Option<B> where
    F: FnMut(<IterMut<'a, T> as Iterator>::Item) -> Option<B>,
    IterMut<'a, T>: Sized, 

pub fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(<IterMut<'a, T> as Iterator>::Item) -> bool,
    IterMut<'a, T>: Sized, 

pub fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(<IterMut<'a, T> as Iterator>::Item) -> bool,
    IterMut<'a, T>: Sized,
    IterMut<'a, T>: ExactSizeIterator,
    IterMut<'a, T>: DoubleEndedIterator, 

impl<'a, T> Iterator for RChunks<'a, T>

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<<RChunks<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<<RChunks<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for RChunksExact<'a, T>

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(
    &mut self,
    n: usize
) -> Option<<RChunksExact<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<<RChunksExact<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for RChunksExactMut<'a, T>

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<&'a mut [T]>

pub fn last(self) -> Option<<RChunksExactMut<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for RChunksMut<'a, T>

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<&'a mut [T]>

pub fn last(self) -> Option<<RChunksMut<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for Windows<'a, T>

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<<Windows<'a, T> as Iterator>::Item>

pub fn last(self) -> Option<<Windows<'a, T> as Iterator>::Item>

impl<'a, T> Iterator for sp_std::sync::mpsc::Iter<'a, T>

type Item = T

pub fn next(&mut self) -> Option<T>

impl<'a, T> Iterator for TryIter<'a, T>

type Item = T

pub fn next(&mut self) -> Option<T>

impl<'a, T, P> Iterator for GroupBy<'a, T, P> where
    T: 'a,
    P: FnMut(&T, &T) -> bool, 

type Item = &'a [T]

pub fn next(&mut self) -> Option<<GroupBy<'a, T, P> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<<GroupBy<'a, T, P> as Iterator>::Item>

impl<'a, T, P> Iterator for GroupByMut<'a, T, P> where
    T: 'a,
    P: FnMut(&T, &T) -> bool, 

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<<GroupByMut<'a, T, P> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<<GroupByMut<'a, T, P> as Iterator>::Item>

impl<'a, T, P> Iterator for sp_std::slice::RSplit<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for RSplitMut<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for sp_std::slice::RSplitN<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for RSplitNMut<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for sp_std::slice::Split<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for SplitMut<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for sp_std::slice::SplitN<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a [T]

pub fn next(&mut self) -> Option<&'a [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, P> Iterator for SplitNMut<'a, T, P> where
    P: FnMut(&T) -> bool, 

type Item = &'a mut [T]

pub fn next(&mut self) -> Option<&'a mut [T]>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<'a, T, const N: usize> Iterator for ArrayChunks<'a, T, N>

type Item = &'a [T; N]

pub fn next(&mut self) -> Option<&'a [T; N]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(
    &mut self,
    n: usize
) -> Option<<ArrayChunks<'a, T, N> as Iterator>::Item>

pub fn last(self) -> Option<<ArrayChunks<'a, T, N> as Iterator>::Item>

pub unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> &'a [T; N]

impl<'a, T, const N: usize> Iterator for ArrayChunksMut<'a, T, N>

type Item = &'a mut [T; N]

pub fn next(&mut self) -> Option<&'a mut [T; N]>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(
    &mut self,
    n: usize
) -> Option<<ArrayChunksMut<'a, T, N> as Iterator>::Item>

pub fn last(self) -> Option<<ArrayChunksMut<'a, T, N> as Iterator>::Item>

pub unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> &'a mut [T; N]

impl<'a, T, const N: usize> Iterator for ArrayWindows<'a, T, N>

type Item = &'a [T; N]

pub fn next(&mut self) -> Option<<ArrayWindows<'a, T, N> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn nth(
    &mut self,
    n: usize
) -> Option<<ArrayWindows<'a, T, N> as Iterator>::Item>

pub fn last(self) -> Option<<ArrayWindows<'a, T, N> as Iterator>::Item>

impl<A> Iterator for Repeat<A> where
    A: Clone, 

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<A> Iterator for sp_std::ops::Range<A> where
    A: Step, 

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<A>

pub fn last(self) -> Option<A>

pub fn min(self) -> Option<A>

pub fn max(self) -> Option<A>

impl<A> Iterator for RangeFrom<A> where
    A: Step, 

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<A>

impl<A> Iterator for RangeInclusive<A> where
    A: Step, 

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<A>

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, <RangeInclusive<A> as Iterator>::Item) -> R,
    RangeInclusive<A>: Sized, 

pub fn fold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, <RangeInclusive<A> as Iterator>::Item) -> B,
    RangeInclusive<A>: Sized, 

pub fn last(self) -> Option<A>

pub fn min(self) -> Option<A>

pub fn max(self) -> Option<A>

impl<A, B> Iterator for sp_std::iter::Chain<A, B> where
    A: Iterator,
    B: Iterator<Item = <A as Iterator>::Item>, 

type Item = <A as Iterator>::Item

pub fn next(&mut self) -> Option<<A as Iterator>::Item>

pub fn count(self) -> usize

pub fn try_fold<Acc, F, R>(&mut self, acc: Acc, f: F) -> R where
    R: Try<Ok = Acc>,
    F: FnMut(Acc, <Chain<A, B> as Iterator>::Item) -> R,
    Chain<A, B>: Sized, 

pub fn fold<Acc, F>(self, acc: Acc, f: F) -> Acc where
    F: FnMut(Acc, <Chain<A, B> as Iterator>::Item) -> Acc, 

pub fn advance_by(&mut self, n: usize) -> Result<(), usize>

🔬 This is a nightly-only experimental API. (iter_advance_by)

recently added

pub fn nth(&mut self, n: usize) -> Option<<Chain<A, B> as Iterator>::Item>

pub fn find<P>(
    &mut self,
    predicate: P
) -> Option<<Chain<A, B> as Iterator>::Item> where
    P: FnMut(&<Chain<A, B> as Iterator>::Item) -> bool, 

pub fn last(self) -> Option<<A as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<A, B> Iterator for Zip<A, B> where
    A: Iterator,
    B: Iterator, 

type Item = (<A as Iterator>::Item, <B as Iterator>::Item)

pub fn next(&mut self) -> Option<<Zip<A, B> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<<Zip<A, B> as Iterator>::Item>

pub unsafe fn __iterator_get_unchecked(
    &mut self,
    idx: usize
) -> <Zip<A, B> as Iterator>::Item where
    Zip<A, B>: TrustedRandomAccess, 

impl<A, F> Iterator for OnceWith<F> where
    F: FnOnce() -> A, 

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<A, F> Iterator for RepeatWith<F> where
    F: FnMut() -> A, 

type Item = A

pub fn next(&mut self) -> Option<A>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<B, I, F> Iterator for FilterMap<I, F> where
    F: FnMut(<I as Iterator>::Item) -> Option<B>,
    I: Iterator, 

type Item = B

pub fn next(&mut self) -> Option<B>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <FilterMap<I, F> as Iterator>::Item) -> R,
    FilterMap<I, F>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <FilterMap<I, F> as Iterator>::Item) -> Acc, 

impl<B, I, F> Iterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: Iterator, 

type Item = B

pub fn next(&mut self) -> Option<B>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> R where
    R: Try<Ok = Acc>,
    G: FnMut(Acc, <Map<I, F> as Iterator>::Item) -> R,
    Map<I, F>: Sized, 

pub fn fold<Acc, G>(self, init: Acc, g: G) -> Acc where
    G: FnMut(Acc, <Map<I, F> as Iterator>::Item) -> Acc, 

pub unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> B where
    Map<I, F>: TrustedRandomAccess, 

impl<B, I, P> Iterator for MapWhile<I, P> where
    I: Iterator,
    P: FnMut(<I as Iterator>::Item) -> Option<B>, 

type Item = B

pub fn next(&mut self) -> Option<B>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <MapWhile<I, P> as Iterator>::Item) -> R,
    MapWhile<I, P>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <MapWhile<I, P> as Iterator>::Item) -> Acc,
    MapWhile<I, P>: Sized, 

impl<B, I, St, F> Iterator for Scan<I, St, F> where
    F: FnMut(&mut St, <I as Iterator>::Item) -> Option<B>,
    I: Iterator, 

type Item = B

pub fn next(&mut self) -> Option<B>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Scan<I, St, F> as Iterator>::Item) -> R,
    Scan<I, St, F>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Scan<I, St, F> as Iterator>::Item) -> Acc,
    Scan<I, St, F>: Sized, 

impl<I> Iterator for Cycle<I> where
    I: Clone + Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, F, R>(&mut self, acc: Acc, f: F) -> R where
    R: Try<Ok = Acc>,
    F: FnMut(Acc, <Cycle<I> as Iterator>::Item) -> R, 

impl<I> Iterator for Enumerate<I> where
    I: Iterator, 

type Item = (usize, <I as Iterator>::Item)

pub fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)>

Overflow Behavior

The method does no guarding against overflows, so enumerating more than usize::MAX elements either produces the wrong result or panics. If debug assertions are enabled, a panic is guaranteed.

Panics

Might panic if the index of the element overflows a usize.

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<(usize, <I as Iterator>::Item)>

pub fn count(self) -> usize

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Enumerate<I> as Iterator>::Item) -> R,
    Enumerate<I>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Enumerate<I> as Iterator>::Item) -> Acc, 

pub unsafe fn __iterator_get_unchecked(
    &mut self,
    idx: usize
) -> <Enumerate<I> as Iterator>::Item where
    Enumerate<I>: TrustedRandomAccess, 

impl<I> Iterator for Fuse<I> where
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<Fuse<I> as Iterator>::Item>

pub fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>

pub fn last(self) -> Option<<Fuse<I> as Iterator>::Item>

pub fn count(self) -> usize

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, acc: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Fuse<I> as Iterator>::Item) -> R,
    Fuse<I>: Sized, 

pub fn fold<Acc, Fold>(self, acc: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Fuse<I> as Iterator>::Item) -> Acc, 

pub fn find<P>(&mut self, predicate: P) -> Option<<Fuse<I> as Iterator>::Item> where
    P: FnMut(&<Fuse<I> as Iterator>::Item) -> bool, 

pub unsafe fn __iterator_get_unchecked(
    &mut self,
    idx: usize
) -> <Fuse<I> as Iterator>::Item where
    Fuse<I>: TrustedRandomAccess, 

impl<I> Iterator for Intersperse<I> where
    I: Iterator,
    <I as Iterator>::Item: Clone, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn fold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, <Intersperse<I> as Iterator>::Item) -> B,
    Intersperse<I>: Sized, 

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<I> Iterator for Peekable<I> where
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn count(self) -> usize

pub fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>

pub fn last(self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, <Peekable<I> as Iterator>::Item) -> R,
    Peekable<I>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Peekable<I> as Iterator>::Item) -> Acc, 

impl<I> Iterator for Rev<I> where
    I: DoubleEndedIterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn advance_by(&mut self, n: usize) -> Result<(), usize>

🔬 This is a nightly-only experimental API. (iter_advance_by)

recently added

pub fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>

pub fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
    R: Try<Ok = B>,
    F: FnMut(B, <Rev<I> as Iterator>::Item) -> R,
    Rev<I>: Sized, 

pub fn fold<Acc, F>(self, init: Acc, f: F) -> Acc where
    F: FnMut(Acc, <Rev<I> as Iterator>::Item) -> Acc, 

pub fn find<P>(&mut self, predicate: P) -> Option<<Rev<I> as Iterator>::Item> where
    P: FnMut(&<Rev<I> as Iterator>::Item) -> bool, 

impl<I> Iterator for Skip<I> where
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>

pub fn count(self) -> usize

pub fn last(self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Skip<I> as Iterator>::Item) -> R,
    Skip<I>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Skip<I> as Iterator>::Item) -> Acc, 

impl<I> Iterator for StepBy<I> where
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<StepBy<I> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<<StepBy<I> as Iterator>::Item>

pub fn try_fold<Acc, F, R>(&mut self, acc: Acc, f: F) -> R where
    R: Try<Ok = Acc>,
    F: FnMut(Acc, <StepBy<I> as Iterator>::Item) -> R, 

pub fn fold<Acc, F>(self, acc: Acc, f: F) -> Acc where
    F: FnMut(Acc, <StepBy<I> as Iterator>::Item) -> Acc, 

impl<I> Iterator for Take<I> where
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Take<I> as Iterator>::Item) -> R,
    Take<I>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Take<I> as Iterator>::Item) -> Acc,
    Take<I>: Sized, 

impl<I, A> Iterator for Box<I, A> where
    A: Allocator,
    I: Iterator + ?Sized, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item>

pub fn last(self) -> Option<<I as Iterator>::Item>

impl<I, F> Iterator for Inspect<I, F> where
    F: FnMut(&<I as Iterator>::Item),
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Inspect<I, F> as Iterator>::Item) -> R,
    Inspect<I, F>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Inspect<I, F> as Iterator>::Item) -> Acc, 

impl<I, G> Iterator for IntersperseWith<I, G> where
    I: Iterator,
    G: FnMut() -> <I as Iterator>::Item, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn fold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, <IntersperseWith<I, G> as Iterator>::Item) -> B,
    IntersperseWith<I, G>: Sized, 

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<I, P> Iterator for Filter<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Filter<I, P> as Iterator>::Item) -> R,
    Filter<I, P>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Filter<I, P> as Iterator>::Item) -> Acc, 

impl<I, P> Iterator for SkipWhile<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <SkipWhile<I, P> as Iterator>::Item) -> R,
    SkipWhile<I, P>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <SkipWhile<I, P> as Iterator>::Item) -> Acc, 

impl<I, P> Iterator for TakeWhile<I, P> where
    I: Iterator,
    P: FnMut(&<I as Iterator>::Item) -> bool, 

type Item = <I as Iterator>::Item

pub fn next(&mut self) -> Option<<I as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <TakeWhile<I, P> as Iterator>::Item) -> R,
    TakeWhile<I, P>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <TakeWhile<I, P> as Iterator>::Item) -> Acc,
    TakeWhile<I, P>: Sized, 

impl<I, U> Iterator for Flatten<I> where
    I: Iterator,
    U: Iterator,
    <I as Iterator>::Item: IntoIterator,
    <<I as Iterator>::Item as IntoIterator>::IntoIter == U,
    <<I as Iterator>::Item as IntoIterator>::Item == <U as Iterator>::Item, 

type Item = <U as Iterator>::Item

pub fn next(&mut self) -> Option<<U as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <Flatten<I> as Iterator>::Item) -> R,
    Flatten<I>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <Flatten<I> as Iterator>::Item) -> Acc, 

impl<I, U, F> Iterator for FlatMap<I, U, F> where
    F: FnMut(<I as Iterator>::Item) -> U,
    I: Iterator,
    U: IntoIterator, 

type Item = <U as IntoIterator>::Item

pub fn next(&mut self) -> Option<<U as IntoIterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
    R: Try<Ok = Acc>,
    Fold: FnMut(Acc, <FlatMap<I, U, F> as Iterator>::Item) -> R,
    FlatMap<I, U, F>: Sized, 

pub fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc where
    Fold: FnMut(Acc, <FlatMap<I, U, F> as Iterator>::Item) -> Acc, 

impl<K, V> Iterator for sp_std::collections::btree_map::IntoIter<K, V>

type Item = (K, V)

pub fn next(&mut self) -> Option<(K, V)>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<K, V> Iterator for sp_std::collections::btree_map::IntoKeys<K, V>

type Item = K

pub fn next(&mut self) -> Option<K>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<K>

pub fn min(self) -> Option<K>

pub fn max(self) -> Option<K>

impl<K, V> Iterator for sp_std::collections::btree_map::IntoValues<K, V>

type Item = V

pub fn next(&mut self) -> Option<V>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn last(self) -> Option<V>

impl<T> Iterator for sp_std::collections::btree_set::IntoIter<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for sp_std::collections::vec_deque::IntoIter<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for Empty<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for Once<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for sp_std::result::IntoIter<T>

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Iterator for sp_std::sync::mpsc::IntoIter<T>

type Item = T

pub fn next(&mut self) -> Option<T>

impl<T, A> Iterator for sp_std::vec::IntoIter<T, A> where
    A: Allocator, 

type Item = T

pub fn next(&mut self) -> Option<T>

pub fn size_hint(&self) -> (usize, Option<usize>)

pub fn count(self) -> usize

pub unsafe fn __iterator_get_unchecked(
    &mut self,
    i: usize
) -> <IntoIter<T, A> as Iterator>::Item where
    IntoIter<T, A>: TrustedRandomAccess, 

impl<T, F> Iterator for FromFn<F> where
    F: FnMut() -> Option<T>, 

type Item = T

pub fn next(&mut self) -> Option<<FromFn<F> as Iterator>::Item>

impl<T, F> Iterator for Successors<T, F> where
    F: FnMut(&T) -> Option<T>, 

type Item = T

pub fn next(&mut self) -> Option<<Successors<T, F> as Iterator>::Item>

pub fn size_hint(&self) -> (usize, Option<usize>)

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