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

#[must_use = "iterator adaptors 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]

Performs copy-assignment from source. Read more

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

The type of the elements being iterated over.

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

Consumes the iterator, returning the last element. Read more

Returns the nth element of the iterator. Read more

Important traits for StepBy<I>

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>

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

Important traits for Zip<A, B>

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

Important traits for Map<I, F>

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

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

Important traits for Filter<I, P>

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

Important traits for FilterMap<I, F>

Creates an iterator that both filters and maps. Read more

Important traits for Enumerate<I>

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

Important traits for Peekable<I>

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>

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

Important traits for TakeWhile<I, P>

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

Important traits for Skip<I>

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

Important traits for Take<I>

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

Important traits for Scan<I, St, F>

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

Important traits for FlatMap<I, U, F>

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

Important traits for Flatten<I>

Creates an iterator that flattens nested structure. Read more

Important traits for Fuse<I>

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

Important traits for Inspect<I, F>

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

Borrows an iterator, rather than consuming it. Read more

Transforms an iterator into a collection. Read more

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

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

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

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

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

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

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

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

Returns the maximum element of an iterator. Read more

Returns the minimum element of an iterator. Read more

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

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

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

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

Important traits for Rev<I>

Reverses an iterator's direction. Read more

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

Important traits for Cloned<I>

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

Important traits for Cycle<I>

Repeats an iterator endlessly. Read more

Sums the elements of an iterator. Read more

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

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

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

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

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

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

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

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

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

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

🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

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

🔬 This is a nightly-only experimental API. (try_from #33417)

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]