pub struct Map<I, F> { /* private fields */ }
Expand description
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> = [1, 2, 3].into_iter().map(|x| x + 1).rev().collect();
assert_eq!(v, [4, 3, 2]);
RunBut 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 ['a', 'b', 'c'].into_iter()
.map(|letter| { c += 1; (letter, c) }) {
println!("{pair:?}");
}
RunThis 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 ['a', 'b', 'c'].into_iter()
.map(|letter| { c += 1; (letter, c) })
.rev() {
println!("{pair:?}");
}
RunTrait Implementations
sourceimpl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F>where
F: FnMut(I::Item) -> B,
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F>where
F: FnMut(I::Item) -> B,
sourcefn next_back(&mut self) -> Option<B>
fn next_back(&mut self) -> Option<B>
sourcefn try_rfold<Acc, G, R>(&mut self, init: Acc, g: G) -> Rwhere
Self: Sized,
G: FnMut(Acc, Self::Item) -> R,
R: Try<Output = Acc>,
fn try_rfold<Acc, G, R>(&mut self, init: Acc, g: G) -> Rwhere
Self: Sized,
G: FnMut(Acc, Self::Item) -> R,
R: Try<Output = Acc>,
Iterator::try_fold()
: it takes
elements starting from the back of the iterator. Read moresourcefn rfold<Acc, G>(self, init: Acc, g: G) -> Accwhere
G: FnMut(Acc, Self::Item) -> Acc,
fn rfold<Acc, G>(self, init: Acc, g: G) -> Accwhere
G: FnMut(Acc, Self::Item) -> Acc,
sourcefn advance_back_by(&mut self, n: usize) -> Result<(), usize>
fn advance_back_by(&mut self, n: usize) -> Result<(), usize>
iter_advance_by
#77404)n
elements. Read moresourceimpl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>where
F: FnMut(I::Item) -> B,
impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>where
F: FnMut(I::Item) -> B,
sourceimpl<B, I: Iterator, F> Iterator for Map<I, F>where
F: FnMut(I::Item) -> B,
impl<B, I: Iterator, F> Iterator for Map<I, F>where
F: FnMut(I::Item) -> B,
type Item = B
type Item = B
sourcefn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
sourcefn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> Rwhere
Self: Sized,
G: FnMut(Acc, Self::Item) -> R,
R: Try<Output = Acc>,
fn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> Rwhere
Self: Sized,
G: FnMut(Acc, Self::Item) -> R,
R: Try<Output = Acc>,
sourcefn fold<Acc, G>(self, init: Acc, g: G) -> Accwhere
G: FnMut(Acc, Self::Item) -> Acc,
fn fold<Acc, G>(self, init: Acc, g: G) -> Accwhere
G: FnMut(Acc, Self::Item) -> Acc,
sourcefn next_chunk<const N: usize>(
&mut self
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
fn next_chunk<const N: usize>(
&mut self
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
iter_next_chunk
#98326)N
values. Read moresourcefn count(self) -> usizewhere
Self: Sized,
fn count(self) -> usizewhere
Self: Sized,
sourcefn last(self) -> Option<Self::Item>where
Self: Sized,
fn last(self) -> Option<Self::Item>where
Self: Sized,
sourcefn advance_by(&mut self, n: usize) -> Result<(), usize>
fn advance_by(&mut self, n: usize) -> Result<(), usize>
iter_advance_by
#77404)n
elements. Read moresourcefn nth(&mut self, n: usize) -> Option<Self::Item>
fn nth(&mut self, n: usize) -> Option<Self::Item>
n
th element of the iterator. Read more1.28.0 · sourcefn step_by(self, step: usize) -> StepBy<Self> ⓘwhere
Self: Sized,
fn step_by(self, step: usize) -> StepBy<Self> ⓘwhere
Self: Sized,
sourcefn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> ⓘwhere
Self: Sized,
U: IntoIterator<Item = Self::Item>,
fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> ⓘwhere
Self: Sized,
U: IntoIterator<Item = Self::Item>,
sourcefn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> ⓘwhere
Self: Sized,
U: IntoIterator,
fn zip<U>(self, other: U) -> Zip<Self, U::IntoIter> ⓘwhere
Self: Sized,
U: IntoIterator,
sourcefn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> ⓘwhere
Self: Sized,
G: FnMut() -> Self::Item,
fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> ⓘwhere
Self: Sized,
G: FnMut() -> Self::Item,
iter_intersperse
#79524)separator
between adjacent items of the original iterator. Read moresourcefn map<B, F>(self, f: F) -> Map<Self, F> ⓘwhere
Self: Sized,
F: FnMut(Self::Item) -> B,
fn map<B, F>(self, f: F) -> Map<Self, F> ⓘwhere
Self: Sized,
F: FnMut(Self::Item) -> B,
1.21.0 · sourcefn for_each<F>(self, f: F)where
Self: Sized,
F: FnMut(Self::Item),
fn for_each<F>(self, f: F)where
Self: Sized,
F: FnMut(Self::Item),
sourcefn filter<P>(self, predicate: P) -> Filter<Self, P> ⓘwhere
Self: Sized,
P: FnMut(&Self::Item) -> bool,
fn filter<P>(self, predicate: P) -> Filter<Self, P> ⓘwhere
Self: Sized,
P: FnMut(&Self::Item) -> bool,
sourcefn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> ⓘwhere
Self: Sized,
F: FnMut(Self::Item) -> Option<B>,
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> ⓘwhere
Self: Sized,
F: FnMut(Self::Item) -> Option<B>,
sourcefn enumerate(self) -> Enumerate<Self> ⓘwhere
Self: Sized,
fn enumerate(self) -> Enumerate<Self> ⓘwhere
Self: Sized,
sourcefn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> ⓘwhere
Self: Sized,
P: FnMut(&Self::Item) -> bool,
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> ⓘwhere
Self: Sized,
P: FnMut(&Self::Item) -> bool,
sourcefn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> ⓘwhere
Self: Sized,
P: FnMut(&Self::Item) -> bool,
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> ⓘwhere
Self: Sized,
P: FnMut(&Self::Item) -> bool,
1.57.0 · sourcefn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> ⓘwhere
Self: Sized,
P: FnMut(Self::Item) -> Option<B>,
fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> ⓘwhere
Self: Sized,
P: FnMut(Self::Item) -> Option<B>,
sourcefn skip(self, n: usize) -> Skip<Self> ⓘwhere
Self: Sized,
fn skip(self, n: usize) -> Skip<Self> ⓘwhere
Self: Sized,
n
elements. Read moresourcefn take(self, n: usize) -> Take<Self> ⓘwhere
Self: Sized,
fn take(self, n: usize) -> Take<Self> ⓘwhere
Self: Sized,
n
elements, or fewer
if the underlying iterator ends sooner. Read moresourcefn 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>,
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>,
sourcefn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> ⓘwhere
Self: Sized,
U: IntoIterator,
F: FnMut(Self::Item) -> U,
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> ⓘwhere
Self: Sized,
U: IntoIterator,
F: FnMut(Self::Item) -> U,
sourcefn inspect<F>(self, f: F) -> Inspect<Self, F> ⓘwhere
Self: Sized,
F: FnMut(&Self::Item),
fn inspect<F>(self, f: F) -> Inspect<Self, F> ⓘwhere
Self: Sized,
F: FnMut(&Self::Item),
sourcefn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
sourcefn collect<B: FromIterator<Self::Item>>(self) -> Bwhere
Self: Sized,
fn collect<B: FromIterator<Self::Item>>(self) -> Bwhere
Self: Sized,
sourcefn collect_into<E: Extend<Self::Item>>(self, collection: &mut E) -> &mut Ewhere
Self: Sized,
fn collect_into<E: Extend<Self::Item>>(self, collection: &mut E) -> &mut Ewhere
Self: Sized,
iter_collect_into
#94780)sourcefn partition<B, F>(self, f: F) -> (B, B)where
Self: Sized,
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,
fn partition<B, F>(self, f: F) -> (B, B)where
Self: Sized,
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,
sourcefn is_partitioned<P>(self, predicate: P) -> boolwhere
Self: Sized,
P: FnMut(Self::Item) -> bool,
fn is_partitioned<P>(self, predicate: P) -> boolwhere
Self: Sized,
P: FnMut(Self::Item) -> bool,
iter_is_partitioned
#62544)true
precede all those that return false
. Read more1.27.0 · sourcefn try_for_each<F, R>(&mut self, f: F) -> Rwhere
Self: Sized,
F: FnMut(Self::Item) -> R,
R: Try<Output = ()>,
fn try_for_each<F, R>(&mut self, f: F) -> Rwhere
Self: Sized,
F: FnMut(Self::Item) -> R,
R: Try<Output = ()>,
1.51.0 · sourcefn reduce<F>(self, f: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(Self::Item, Self::Item) -> Self::Item,
fn reduce<F>(self, f: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(Self::Item, Self::Item) -> Self::Item,
sourcefn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<R::Output>>>::TryTypewhere
Self: Sized,
F: FnMut(Self::Item, Self::Item) -> R,
R: Try<Output = Self::Item>,
R::Residual: Residual<Option<Self::Item>>,
fn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<R::Output>>>::TryTypewhere
Self: Sized,
F: FnMut(Self::Item, Self::Item) -> R,
R: Try<Output = Self::Item>,
R::Residual: Residual<Option<Self::Item>>,
iterator_try_reduce
#87053)sourcefn all<F>(&mut self, f: F) -> boolwhere
Self: Sized,
F: FnMut(Self::Item) -> bool,
fn all<F>(&mut self, f: F) -> boolwhere
Self: Sized,
F: FnMut(Self::Item) -> bool,
sourcefn any<F>(&mut self, f: F) -> boolwhere
Self: Sized,
F: FnMut(Self::Item) -> bool,
fn any<F>(&mut self, f: F) -> boolwhere
Self: Sized,
F: FnMut(Self::Item) -> bool,
sourcefn find<P>(&mut self, predicate: P) -> Option<Self::Item>where
Self: Sized,
P: FnMut(&Self::Item) -> bool,
fn find<P>(&mut self, predicate: P) -> Option<Self::Item>where
Self: Sized,
P: FnMut(&Self::Item) -> bool,
1.30.0 · sourcefn find_map<B, F>(&mut self, f: F) -> Option<B>where
Self: Sized,
F: FnMut(Self::Item) -> Option<B>,
fn find_map<B, F>(&mut self, f: F) -> Option<B>where
Self: Sized,
F: FnMut(Self::Item) -> Option<B>,
sourcefn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryTypewhere
Self: Sized,
F: FnMut(&Self::Item) -> R,
R: Try<Output = bool>,
R::Residual: Residual<Option<Self::Item>>,
fn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryTypewhere
Self: Sized,
F: FnMut(&Self::Item) -> R,
R: Try<Output = bool>,
R::Residual: Residual<Option<Self::Item>>,
try_find
#63178)sourcefn position<P>(&mut self, predicate: P) -> Option<usize>where
Self: Sized,
P: FnMut(Self::Item) -> bool,
fn position<P>(&mut self, predicate: P) -> Option<usize>where
Self: Sized,
P: FnMut(Self::Item) -> bool,
1.6.0 · sourcefn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item) -> B,
fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item) -> B,
1.15.0 · sourcefn max_by<F>(self, compare: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
fn max_by<F>(self, compare: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
1.6.0 · sourcefn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item) -> B,
fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item) -> B,
1.15.0 · sourcefn min_by<F>(self, compare: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
fn min_by<F>(self, compare: F) -> Option<Self::Item>where
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
sourcefn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Sized + Iterator<Item = (A, B)>,
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Sized + Iterator<Item = (A, B)>,
1.36.0 · sourcefn copied<'a, T: 'a>(self) -> Copied<Self> ⓘwhere
Self: Sized + Iterator<Item = &'a T>,
T: Copy,
fn copied<'a, T: 'a>(self) -> Copied<Self> ⓘwhere
Self: Sized + Iterator<Item = &'a T>,
T: Copy,
sourcefn cloned<'a, T: 'a>(self) -> Cloned<Self> ⓘwhere
Self: Sized + Iterator<Item = &'a T>,
T: Clone,
fn cloned<'a, T: 'a>(self) -> Cloned<Self> ⓘwhere
Self: Sized + Iterator<Item = &'a T>,
T: Clone,
sourcefn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N> ⓘwhere
Self: Sized,
fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N> ⓘwhere
Self: Sized,
iter_array_chunks
#100450)N
elements of the iterator at a time. Read more1.11.0 · sourcefn sum<S>(self) -> Swhere
Self: Sized,
S: Sum<Self::Item>,
fn sum<S>(self) -> Swhere
Self: Sized,
S: Sum<Self::Item>,
1.11.0 · sourcefn product<P>(self) -> Pwhere
Self: Sized,
P: Product<Self::Item>,
fn product<P>(self) -> Pwhere
Self: Sized,
P: Product<Self::Item>,
sourcefn cmp_by<I, F>(self, other: I, cmp: F) -> Orderingwhere
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, I::Item) -> Ordering,
fn cmp_by<I, F>(self, other: I, cmp: F) -> Orderingwhere
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, I::Item) -> Ordering,
iter_order_by
#64295)Iterator
with those
of another with respect to the specified comparison function. Read more1.5.0 · sourcefn partial_cmp<I>(self, other: I) -> Option<Ordering>where
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
fn partial_cmp<I>(self, other: I) -> Option<Ordering>where
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
sourcefn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>where
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, I::Item) -> Option<Ordering>,
fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>where
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, I::Item) -> Option<Ordering>,
iter_order_by
#64295)Iterator
with those
of another with respect to the specified comparison function. Read more1.5.0 · sourcefn eq<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialEq<I::Item>,
Self: Sized,
fn eq<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialEq<I::Item>,
Self: Sized,
sourcefn eq_by<I, F>(self, other: I, eq: F) -> boolwhere
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, I::Item) -> bool,
fn eq_by<I, F>(self, other: I, eq: F) -> boolwhere
Self: Sized,
I: IntoIterator,
F: FnMut(Self::Item, I::Item) -> bool,
iter_order_by
#64295)1.5.0 · sourcefn ne<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialEq<I::Item>,
Self: Sized,
fn ne<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialEq<I::Item>,
Self: Sized,
1.5.0 · sourcefn lt<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
fn lt<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
Iterator
are lexicographically
less than those of another. Read more1.5.0 · sourcefn le<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
fn le<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
Iterator
are lexicographically
less or equal to those of another. Read more1.5.0 · sourcefn gt<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
fn gt<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
Iterator
are lexicographically
greater than those of another. Read more1.5.0 · sourcefn ge<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
fn ge<I>(self, other: I) -> boolwhere
I: IntoIterator,
Self::Item: PartialOrd<I::Item>,
Self: Sized,
Iterator
are lexicographically
greater than or equal to those of another. Read moresourcefn is_sorted_by<F>(self, compare: F) -> boolwhere
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
fn is_sorted_by<F>(self, compare: F) -> boolwhere
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
is_sorted
#53485)sourcefn is_sorted_by_key<F, K>(self, f: F) -> boolwhere
Self: Sized,
F: FnMut(Self::Item) -> K,
K: PartialOrd,
fn is_sorted_by_key<F, K>(self, f: F) -> boolwhere
Self: Sized,
F: FnMut(Self::Item) -> K,
K: PartialOrd,
is_sorted
#53485)