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1.0.0[][src]Struct core::iter::Map

#[must_use = "iterators are lazy and do nothing unless consumed"]
pub struct Map<I, F> { /* fields omitted */ }

An iterator that maps the values of iter with f.

This struct is created by the map method on Iterator. See its documentation for more.

Notes about side effects

The map iterator implements DoubleEndedIterator, meaning that you can also map backwards:

let v: Vec<i32> = vec![1, 2, 3].into_iter().map(|x| x + 1).rev().collect();

assert_eq!(v, [4, 3, 2]);Run

But if your closure has state, iterating backwards may act in a way you do not expect. Let's go through an example. First, in the forward direction:

let mut c = 0;

for pair in vec!['a', 'b', 'c'].into_iter()
                               .map(|letter| { c += 1; (letter, c) }) {
    println!("{:?}", pair);
}Run

This will print "('a', 1), ('b', 2), ('c', 3)".

Now consider this twist where we add a call to rev. This version will print ('c', 1), ('b', 2), ('a', 3). Note that the letters are reversed, but the values of the counter still go in order. This is because map() is still being called lazily on each item, but we are popping items off the back of the vector now, instead of shifting them from the front.

let mut c = 0;

for pair in vec!['a', 'b', 'c'].into_iter()
                               .map(|letter| { c += 1; (letter, c) })
                               .rev() {
    println!("{:?}", pair);
}Run

Trait Implementations

impl<I: Clone, F: Clone> Clone for Map<I, F>[src]

fn clone_from(&mut self, source: &Self)[src]

Performs copy-assignment from source. Read more

impl<B, I: Iterator, F> Iterator for Map<I, F> where
    F: FnMut(I::Item) -> B, 
[src]

type Item = B

The type of the elements being iterated over.

fn count(self) -> usize where
    Self: Sized
[src]

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

fn last(self) -> Option<Self::Item> where
    Self: Sized
[src]

Consumes the iterator, returning the last element. Read more

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

Returns the nth element of the iterator. Read more

Important traits for StepBy<I>
fn step_by(self, step: usize) -> StepBy<Self> where
    Self: Sized
1.28.0
[src]

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

Important traits for Chain<A, B>
fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> where
    Self: Sized,
    U: IntoIterator<Item = Self::Item>, 
[src]

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

Important traits for Zip<A, B>
fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> where
    Self: Sized,
    U: IntoIterator
[src]

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

Important traits for Map<I, F>
fn map<B, F>(self, f: F) -> Map<Self, F> where
    Self: Sized,
    F: FnMut(Self::Item) -> B, 
[src]

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

fn for_each<F>(self, f: F) where
    Self: Sized,
    F: FnMut(Self::Item), 
1.21.0
[src]

Calls a closure on each element of an iterator. Read more

Important traits for Filter<I, P>
fn filter<P>(self, predicate: P) -> Filter<Self, P> where
    Self: Sized,
    P: FnMut(&Self::Item) -> bool, 
[src]

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

Important traits for FilterMap<I, F>
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
    Self: Sized,
    F: FnMut(Self::Item) -> Option<B>, 
[src]

Creates an iterator that both filters and maps. Read more

Important traits for Enumerate<I>
fn enumerate(self) -> Enumerate<Self> where
    Self: Sized
[src]

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

Important traits for Peekable<I>
fn peekable(self) -> Peekable<Self> where
    Self: Sized
[src]

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

Important traits for SkipWhile<I, P>
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
    Self: Sized,
    P: FnMut(&Self::Item) -> bool, 
[src]

Creates an iterator that [skip]s elements based on a predicate. Read more

Important traits for TakeWhile<I, P>
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
    Self: Sized,
    P: FnMut(&Self::Item) -> bool, 
[src]

Creates an iterator that yields elements based on a predicate. Read more

Important traits for Skip<I>
fn skip(self, n: usize) -> Skip<Self> where
    Self: Sized
[src]

Creates an iterator that skips the first n elements. Read more

Important traits for Take<I>
fn take(self, n: usize) -> Take<Self> where
    Self: Sized
[src]

Creates an iterator that yields its first n elements. Read more

Important traits for Scan<I, St, F>
fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
    Self: Sized,
    F: FnMut(&mut St, Self::Item) -> Option<B>, 
[src]

An iterator adaptor similar to [fold] that holds internal state and produces a new iterator. Read more

Important traits for FlatMap<I, U, F>
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
    Self: Sized,
    U: IntoIterator,
    F: FnMut(Self::Item) -> U, 
[src]

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

Important traits for Flatten<I>
fn flatten(self) -> Flatten<Self> where
    Self: Sized,
    Self::Item: IntoIterator
1.29.0
[src]

Creates an iterator that flattens nested structure. Read more

Important traits for Fuse<I>
fn fuse(self) -> Fuse<Self> where
    Self: Sized
[src]

Creates an iterator which ends after the first [None]. Read more

Important traits for Inspect<I, F>
fn inspect<F>(self, f: F) -> Inspect<Self, F> where
    Self: Sized,
    F: FnMut(&Self::Item), 
[src]

Do something with each element of an iterator, passing the value on. Read more

fn by_ref(&mut self) -> &mut Self where
    Self: Sized
[src]

Borrows an iterator, rather than consuming it. Read more

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

Transforms an iterator into a collection. Read more

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

Consumes an iterator, creating two collections from it. Read more

fn try_for_each<F, R>(&mut self, f: F) -> R where
    Self: Sized,
    F: FnMut(Self::Item) -> R,
    R: Try<Ok = ()>, 
1.27.0
[src]

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

fn all<F>(&mut self, f: F) -> bool where
    Self: Sized,
    F: FnMut(Self::Item) -> bool, 
[src]

Tests if every element of the iterator matches a predicate. Read more

fn any<F>(&mut self, f: F) -> bool where
    Self: Sized,
    F: FnMut(Self::Item) -> bool, 
[src]

Tests if any element of the iterator matches a predicate. Read more

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

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

fn find_map<B, F>(&mut self, f: F) -> Option<B> where
    Self: Sized,
    F: FnMut(Self::Item) -> Option<B>, 
1.30.0
[src]

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

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

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

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

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

fn max(self) -> Option<Self::Item> where
    Self: Sized,
    Self::Item: Ord
[src]

Returns the maximum element of an iterator. Read more

fn min(self) -> Option<Self::Item> where
    Self: Sized,
    Self::Item: Ord
[src]

Returns the minimum element of an iterator. Read more

fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item> where
    Self: Sized,
    F: FnMut(&Self::Item) -> B, 
1.6.0
[src]

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

fn max_by<F>(self, compare: F) -> Option<Self::Item> where
    Self: Sized,
    F: FnMut(&Self::Item, &Self::Item) -> Ordering
1.15.0
[src]

Returns the element that gives the maximum value with respect to the specified comparison function. Read more

fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item> where
    Self: Sized,
    F: FnMut(&Self::Item) -> B, 
1.6.0
[src]

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

fn min_by<F>(self, compare: F) -> Option<Self::Item> where
    Self: Sized,
    F: FnMut(&Self::Item, &Self::Item) -> Ordering
1.15.0
[src]

Returns the element that gives the minimum value with respect to the specified comparison function. Read more

Important traits for Rev<I>
fn rev(self) -> Rev<Self> where
    Self: Sized + DoubleEndedIterator
[src]

Reverses an iterator's direction. Read more

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

Converts an iterator of pairs into a pair of containers. Read more

Important traits for Copied<I>
fn copied<'a, T: 'a>(self) -> Copied<Self> where
    Self: Sized + Iterator<Item = &'a T>,
    T: Copy
[src]

🔬 This is a nightly-only experimental API. (iter_copied #57127)

Creates an iterator which copies all of its elements. Read more

Important traits for Cloned<I>
fn cloned<'a, T: 'a>(self) -> Cloned<Self> where
    Self: Sized + Iterator<Item = &'a T>,
    T: Clone
[src]

Creates an iterator which [clone]s all of its elements. Read more

Important traits for Cycle<I>
fn cycle(self) -> Cycle<Self> where
    Self: Sized + Clone
[src]

Repeats an iterator endlessly. Read more

fn sum<S>(self) -> S where
    Self: Sized,
    S: Sum<Self::Item>, 
1.11.0
[src]

Sums the elements of an iterator. Read more

fn product<P>(self) -> P where
    Self: Sized,
    P: Product<Self::Item>, 
1.11.0
[src]

Iterates over the entire iterator, multiplying all the elements Read more

fn cmp<I>(self, other: I) -> Ordering where
    I: IntoIterator<Item = Self::Item>,
    Self::Item: Ord,
    Self: Sized
1.5.0
[src]

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

fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
    I: IntoIterator,
    Self::Item: PartialOrd<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn eq<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn ne<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn lt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn le<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn gt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn ge<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<I::Item>,
    Self: Sized
1.5.0
[src]

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

fn is_sorted(self) -> bool where
    Self: Sized,
    Self::Item: PartialOrd
[src]

🔬 This is a nightly-only experimental API. (is_sorted #53485)

new API

Checks if the elements of this iterator are sorted. Read more

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

🔬 This is a nightly-only experimental API. (is_sorted #53485)

new API

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

fn is_sorted_by_key<F, K>(self, f: F) -> bool where
    Self: Sized,
    F: FnMut(&Self::Item) -> K,
    K: PartialOrd
[src]

🔬 This is a nightly-only experimental API. (is_sorted #53485)

new API

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

impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F> where
    F: FnMut(I::Item) -> B, 
[src]

fn nth_back(&mut self, n: usize) -> Option<Self::Item>[src]

🔬 This is a nightly-only experimental API. (iter_nth_back #56995)

Returns the nth element from the end of the iterator. Read more

fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item> where
    Self: Sized,
    P: FnMut(&Self::Item) -> bool, 
1.27.0
[src]

Searches for an element of an iterator from the back that satisfies a predicate. Read more

impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F> where
    F: FnMut(I::Item) -> B, 
[src]

impl<B, I: FusedIterator, F> FusedIterator for Map<I, F> where
    F: FnMut(I::Item) -> B, 
1.26.0
[src]

impl<B, I, F> TrustedLen for Map<I, F> where
    I: TrustedLen,
    F: FnMut(I::Item) -> B, 
[src]

impl<I: Debug, F> Debug for Map<I, F>
1.9.0
[src]

Auto Trait Implementations

impl<I, F> Send for Map<I, F> where
    F: Send,
    I: Send

impl<I, F> Sync for Map<I, F> where
    F: Sync,
    I: Sync

Blanket Implementations

impl<T, U> Into for T where
    U: From<T>, 
[src]

impl<T> From for T[src]

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T, U> TryFrom for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T> Borrow for T where
    T: ?Sized
[src]

impl<T> BorrowMut for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]