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§
source§impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F>
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F>
source§fn next_back(&mut self) -> Option<B>
fn next_back(&mut self) -> Option<B>
source§fn try_rfold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
fn try_rfold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
Iterator::try_fold()
: it takes
elements starting from the back of the iterator. Read moresource§fn rfold<Acc, G>(self, init: Acc, g: G) -> Acc
fn rfold<Acc, G>(self, init: Acc, g: G) -> Acc
source§fn advance_back_by(&mut self, n: usize) -> Result<(), NonZeroUsize>
fn advance_back_by(&mut self, n: usize) -> Result<(), NonZeroUsize>
iter_advance_by
#77404)n
elements. Read moresource§impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
source§impl<B, I: Iterator, F> Iterator for Map<I, F>
impl<B, I: Iterator, F> Iterator for Map<I, F>
source§fn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
source§fn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
fn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
source§fn fold<Acc, G>(self, init: Acc, g: G) -> Acc
fn fold<Acc, G>(self, init: Acc, g: G) -> Acc
source§fn 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 moresource§fn count(self) -> usizewhere
Self: Sized,
fn count(self) -> usizewhere
Self: Sized,
source§fn last(self) -> Option<Self::Item>where
Self: Sized,
fn last(self) -> Option<Self::Item>where
Self: Sized,
source§fn advance_by(&mut self, n: usize) -> Result<(), NonZeroUsize>
fn advance_by(&mut self, n: usize) -> Result<(), NonZeroUsize>
iter_advance_by
#77404)n
elements. Read moresource§fn 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 · source§fn step_by(self, step: usize) -> StepBy<Self> ⓘwhere
Self: Sized,
fn step_by(self, step: usize) -> StepBy<Self> ⓘwhere
Self: Sized,
source§fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> ⓘ
fn chain<U>(self, other: U) -> Chain<Self, U::IntoIter> ⓘ
source§fn 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,
source§fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> ⓘ
fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> ⓘ
iter_intersperse
#79524)separator
between adjacent items of the original iterator. Read moresource§fn map<B, F>(self, f: F) -> Map<Self, F> ⓘ
fn map<B, F>(self, f: F) -> Map<Self, F> ⓘ
source§fn filter<P>(self, predicate: P) -> Filter<Self, P> ⓘ
fn filter<P>(self, predicate: P) -> Filter<Self, P> ⓘ
source§fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> ⓘ
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> ⓘ
source§fn enumerate(self) -> Enumerate<Self> ⓘwhere
Self: Sized,
fn enumerate(self) -> Enumerate<Self> ⓘwhere
Self: Sized,
source§fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> ⓘ
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> ⓘ
source§fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> ⓘ
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> ⓘ
1.57.0 · source§fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> ⓘ
fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> ⓘ
source§fn skip(self, n: usize) -> Skip<Self> ⓘwhere
Self: Sized,
fn skip(self, n: usize) -> Skip<Self> ⓘwhere
Self: Sized,
n
elements. Read moresource§fn 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 moresource§fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> ⓘ
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> ⓘ
source§fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N> ⓘ
fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N> ⓘ
iter_map_windows
#87155)f
for each contiguous window of size N
over
self
and returns an iterator over the outputs of f
. Like slice::windows()
,
the windows during mapping overlap as well. Read moresource§fn inspect<F>(self, f: F) -> Inspect<Self, F> ⓘ
fn inspect<F>(self, f: F) -> Inspect<Self, F> ⓘ
source§fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
fn by_ref(&mut self) -> &mut Selfwhere
Self: Sized,
source§fn collect<B: FromIterator<Self::Item>>(self) -> Bwhere
Self: Sized,
fn collect<B: FromIterator<Self::Item>>(self) -> Bwhere
Self: Sized,
source§fn 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)source§fn partition<B, F>(self, f: F) -> (B, B)
fn partition<B, F>(self, f: F) -> (B, B)
source§fn is_partitioned<P>(self, predicate: P) -> bool
fn is_partitioned<P>(self, predicate: P) -> bool
iter_is_partitioned
#62544)true
precede all those that return false
. Read more1.27.0 · source§fn try_for_each<F, R>(&mut self, f: F) -> R
fn try_for_each<F, R>(&mut self, f: F) -> R
1.51.0 · source§fn reduce<F>(self, f: F) -> Option<Self::Item>
fn reduce<F>(self, f: F) -> Option<Self::Item>
source§fn try_reduce<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<R::Output>>>::TryType
fn try_reduce<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<R::Output>>>::TryType
iterator_try_reduce
#87053)source§fn all<F>(&mut self, f: F) -> bool
fn all<F>(&mut self, f: F) -> bool
source§fn any<F>(&mut self, f: F) -> bool
fn any<F>(&mut self, f: F) -> bool
source§fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
1.30.0 · source§fn find_map<B, F>(&mut self, f: F) -> Option<B>
fn find_map<B, F>(&mut self, f: F) -> Option<B>
source§fn try_find<F, R>(
&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
fn try_find<F, R>( &mut self, f: F ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType
try_find
#63178)source§fn position<P>(&mut self, predicate: P) -> Option<usize>
fn position<P>(&mut self, predicate: P) -> Option<usize>
1.6.0 · source§fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
fn max_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
1.15.0 · source§fn max_by<F>(self, compare: F) -> Option<Self::Item>
fn max_by<F>(self, compare: F) -> Option<Self::Item>
1.6.0 · source§fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
fn min_by_key<B: Ord, F>(self, f: F) -> Option<Self::Item>
1.15.0 · source§fn min_by<F>(self, compare: F) -> Option<Self::Item>
fn min_by<F>(self, compare: F) -> Option<Self::Item>
source§fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)
1.36.0 · source§fn copied<'a, T>(self) -> Copied<Self> ⓘ
fn copied<'a, T>(self) -> Copied<Self> ⓘ
source§fn 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 · source§fn product<P>(self) -> P
fn product<P>(self) -> P
source§fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering
iter_order_by
#64295)Iterator
with those
of another with respect to the specified comparison function. Read more1.5.0 · source§fn partial_cmp<I>(self, other: I) -> Option<Ordering>
fn partial_cmp<I>(self, other: I) -> Option<Ordering>
PartialOrd
elements of
this Iterator
with those of another. The comparison works like short-circuit
evaluation, returning a result without comparing the remaining elements.
As soon as an order can be determined, the evaluation stops and a result is returned. Read moresource§fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>
fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>
iter_order_by
#64295)Iterator
with those
of another with respect to the specified comparison function. Read moresource§fn eq_by<I, F>(self, other: I, eq: F) -> bool
fn eq_by<I, F>(self, other: I, eq: F) -> bool
iter_order_by
#64295)1.5.0 · source§fn lt<I>(self, other: I) -> bool
fn lt<I>(self, other: I) -> bool
Iterator
are lexicographically
less than those of another. Read more1.5.0 · source§fn le<I>(self, other: I) -> bool
fn le<I>(self, other: I) -> bool
Iterator
are lexicographically
less or equal to those of another. Read more1.5.0 · source§fn gt<I>(self, other: I) -> bool
fn gt<I>(self, other: I) -> bool
Iterator
are lexicographically
greater than those of another. Read more1.5.0 · source§fn ge<I>(self, other: I) -> bool
fn ge<I>(self, other: I) -> bool
Iterator
are lexicographically
greater than or equal to those of another. Read moresource§fn is_sorted_by<F>(self, compare: F) -> bool
fn is_sorted_by<F>(self, compare: F) -> bool
is_sorted
#53485)