Struct bitflags::__core::iter::Map

#[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:

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:

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.

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

fn len(&self) -> usize

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

type Item = B

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

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

fn count(self) -> usize

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

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

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

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

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

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

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

fn enumerate(self) -> Enumerate<Self>

fn peekable(self) -> Peekable<Self>

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

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

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

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

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

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

fn fuse(self) -> Fuse<Self>

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Derived Implementations

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

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

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