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

#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Map<I, F> {
    // some 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:

fn main() { let v: Vec<i32> = vec![1, 2, 3].into_iter().rev().map(|x| x + 1).collect(); assert_eq!(v, [4, 3, 2]); }
let v: Vec<i32> = vec![1, 2, 3].into_iter().rev().map(|x| x + 1).collect();

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

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:

fn main() { let mut c = 0; for pair in vec!['a', 'b', 'c'].into_iter() .map(|letter| { c += 1; (letter, c) }) { println!("{:?}", pair); } }
let mut c = 0;

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

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 lazilly on each item, but we are popping items off the back of the vector now, instead of shifting them from the front.

fn main() { let mut c = 0; for pair in vec!['a', 'b', 'c'].into_iter() .map(|letter| { c += 1; (letter, c) }) .rev() { println!("{:?}", pair); } }
let mut c = 0;

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

Trait Implementations

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

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

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 next(&mut self) -> Option<B>

Advances the iterator and returns the next value. Read more

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

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

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

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

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

Consumes the iterator, returning the last element. Read more

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

Consumes the n first elements of the iterator, then returns the next() one. Read more

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

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

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

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

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

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

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

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

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

Creates an iterator that both filters and maps. Read more

fn enumerate(self) -> Enumerate<Self> where Self: Sized

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

fn peekable(self) -> Peekable<Self> where Self: Sized

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

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

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

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

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

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

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

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

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

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>

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

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

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

fn fuse(self) -> Fuse<Self> where Self: Sized

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

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

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

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

Borrows an iterator, rather than consuming it. Read more

fn collect<B: FromIterator<Self::Item>>(self) -> B where Self: Sized

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

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

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

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

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

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

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

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

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

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

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

Returns the maximum element of an iterator. Read more

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

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

Returns the element that gives the maximum value from the specified 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

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

fn rev(self) -> Rev<Self> where Self: Sized + DoubleEndedIterator

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)>

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

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

Creates an iterator which clone()s all of its elements. Read more

fn cycle(self) -> Cycle<Self> where Self: Sized + Clone

Repeats an iterator endlessly. Read more

fn sum<S>(self) -> S where S: Add<Self::Item, Output=S> + Zero, Self: Sized

Sums the elements of an iterator. Read more

fn product<P>(self) -> P where P: Mul<Self::Item, Output=P> + One, Self: Sized

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

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

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

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

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

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

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

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

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]

fn next_back(&mut self) -> Option<B>

An iterator able to yield elements from both ends. Read more

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

fn len(&self) -> usize

Returns the exact number of times the iterator will iterate. Read more

Derived Implementations

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

fn clone(&self) -> Map<I, F>

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more