Struct std::iter::Map1.0.0 [] [src]

#[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<B, I, F> TrustedLen for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: TrustedLen
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impl<I, F> Debug for Map<I, F> where
    I: Debug
1.9.0
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Formats the value using the given formatter.

impl<I, F> Clone for Map<I, F> where
    F: Clone,
    I: Clone
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Returns a copy of the value. Read more

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Performs copy-assignment from source. Read more

impl<B, I, F> FusedIterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: FusedIterator
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impl<B, I, F> Iterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: Iterator
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The type of the elements being iterated over.

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Advances the iterator and returns the next value. Read more

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Returns the bounds on the remaining length of the iterator. Read more

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

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

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Consumes the iterator, returning the last element. Read more

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Returns the nth element of the iterator. Read more

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🔬 This is a nightly-only experimental API. (iterator_step_by #27741)

unstable replacement of Range::step_by

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

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

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

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

1.21.0
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Calls a closure on each element of an iterator. Read more

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

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Creates an iterator that both filters and maps. Read more

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

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

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

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

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

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

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

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

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

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

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Borrows an iterator, rather than consuming it. Read more

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Transforms an iterator into a collection. Read more

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

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

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

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

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

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

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Returns the maximum element of an iterator. Read more

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Returns the minimum element of an iterator. Read more

1.6.0
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Returns the element that gives the maximum value from the specified function. Read more

1.15.0
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Returns the element that gives the maximum value with respect to the specified comparison function. Read more

1.6.0
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Returns the element that gives the minimum value from the specified function. Read more

1.15.0
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Returns the element that gives the minimum value with respect to the specified comparison function. Read more

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Reverses an iterator's direction. Read more

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

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

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Repeats an iterator endlessly. Read more

1.11.0
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Sums the elements of an iterator. Read more

1.11.0
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Iterates over the entire iterator, multiplying all the elements Read more

1.5.0
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Lexicographically compares the elements of this Iterator with those of another. Read more

1.5.0
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Lexicographically compares the elements of this Iterator with those of another. Read more

1.5.0
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Determines if the elements of this Iterator are equal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are unequal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically less than those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically less or equal to those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically greater than those of another. Read more

1.5.0
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Determines if the elements of this Iterator are lexicographically greater than or equal to those of another. Read more

impl<B, I, F> ExactSizeIterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: ExactSizeIterator
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Returns the exact number of times the iterator will iterate. Read more

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🔬 This is a nightly-only experimental API. (exact_size_is_empty #35428)

Returns whether the iterator is empty. Read more

impl<B, I, F> DoubleEndedIterator for Map<I, F> where
    F: FnMut(<I as Iterator>::Item) -> B,
    I: DoubleEndedIterator
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Removes and returns an element from the end of the iterator. Read more

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🔬 This is a nightly-only experimental API. (iter_rfold #44705)

An iterator method that reduces the iterator's elements to a single, final value, starting from the back. Read more

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🔬 This is a nightly-only experimental API. (iter_rfind #39480)

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