Primitive Type array1.0.0[−]
A fixed-size array, denoted [T; N]
, for the element type, T
, and the
non-negative compile-time constant size, N
.
There are two syntactic forms for creating an array:
- A list with each element, i.e.,
[x, y, z]
. - A repeat expression
[x; N]
, which produces an array withN
copies ofx
. The type ofx
must beCopy
.
Note that [expr; 0]
is allowed, and produces an empty array.
This will still evaluate expr
, however, and immediately drop the resulting value, so
be mindful of side effects.
Arrays of any size implement the following traits if the element type allows it:
Copy
Clone
Debug
IntoIterator
(implemented for[T; N]
,&[T; N]
and&mut [T; N]
)PartialEq
,PartialOrd
,Eq
,Ord
Hash
AsRef
,AsMut
Borrow
,BorrowMut
Arrays of sizes from 0 to 32 (inclusive) implement the Default
trait
if the element type allows it. As a stopgap, trait implementations are
statically generated up to size 32.
Arrays coerce to slices ([T]
), so a slice method may be called on
an array. Indeed, this provides most of the API for working with arrays.
Slices have a dynamic size and do not coerce to arrays.
You can move elements out of an array with a slice pattern. If you want
one element, see mem::replace
.
Examples
let mut array: [i32; 3] = [0; 3]; array[1] = 1; array[2] = 2; assert_eq!([1, 2], &array[1..]); // This loop prints: 0 1 2 for x in array { print!("{} ", x); }Run
You can also iterate over reference to the array’s elements:
let array: [i32; 3] = [0; 3]; for x in &array { }Run
You can use a slice pattern to move elements out of an array:
fn move_away(_: String) { /* Do interesting things. */ } let [john, roa] = ["John".to_string(), "Roa".to_string()]; move_away(john); move_away(roa);Run
Editions
Prior to Rust 1.53, arrays did not implement IntoIterator
by value, so the method call
array.into_iter()
auto-referenced into a slice iterator. Right now, the old behavior
is preserved in the 2015 and 2018 editions of Rust for compatibility, ignoring
IntoIterator
by value. In the future, the behavior on the 2015 and 2018 edition
might be made consistent to the behavior of later editions.
let array: [i32; 3] = [0; 3]; // This creates a slice iterator, producing references to each value. for item in array.into_iter().enumerate() { let (i, x): (usize, &i32) = item; println!("array[{}] = {}", i, x); } // The `array_into_iter` lint suggests this change for future compatibility: for item in array.iter().enumerate() { let (i, x): (usize, &i32) = item; println!("array[{}] = {}", i, x); } // You can explicitly iterate an array by value using // `IntoIterator::into_iter` or `std::array::IntoIter::new`: for item in IntoIterator::into_iter(array).enumerate() { let (i, x): (usize, i32) = item; println!("array[{}] = {}", i, x); }Run
Starting in the 2021 edition, array.into_iter()
will use IntoIterator
normally to iterate
by value, and iter()
should be used to iterate by reference like previous editions.
let array: [i32; 3] = [0; 3]; // This iterates by reference: for item in array.iter().enumerate() { let (i, x): (usize, &i32) = item; println!("array[{}] = {}", i, x); } // This iterates by value: for item in array.into_iter().enumerate() { let (i, x): (usize, i32) = item; println!("array[{}] = {}", i, x); }Run
Future language versions might start treating the array.into_iter()
syntax on editions 2015 and 2018 the same as on edition 2021. So code using
those older editions should still be written with this change in mind, to
prevent breakage in the future. The safest way to accomplish this is to
avoid the into_iter
syntax on those editions. If an edition update is not
viable/desired, there are multiple alternatives:
- use
iter
, equivalent to the old behavior, creating references - use
array::IntoIter
, equivalent to the post-2021 behavior (Rust 1.51+) - replace
for ... in array.into_iter() {
withfor ... in array {
, equivalent to the post-2021 behavior (Rust 1.53+)
use std::array::IntoIter; let array: [i32; 3] = [0; 3]; // This iterates by reference: for item in array.iter() { let x: &i32 = item; println!("{}", x); } // This iterates by value: for item in IntoIter::new(array) { let x: i32 = item; println!("{}", x); } // This iterates by value: for item in array { let x: i32 = item; println!("{}", x); } // IntoIter can also start a chain. // This iterates by value: for item in IntoIter::new(array).enumerate() { let (i, x): (usize, i32) = item; println!("array[{}] = {}", i, x); }Run
Implementations
impl<T, const N: usize> [T; N]
[src]
impl<T, const N: usize> [T; N]
[src]pub fn map<F, U>(self, f: F) -> [U; N] where
F: FnMut(T) -> U,
[src]
F: FnMut(T) -> U,
Returns an array of the same size as self
, with function f
applied to each element
in order.
Examples
#![feature(array_map)] let x = [1, 2, 3]; let y = x.map(|v| v + 1); assert_eq!(y, [2, 3, 4]); let x = [1, 2, 3]; let mut temp = 0; let y = x.map(|v| { temp += 1; v * temp }); assert_eq!(y, [1, 4, 9]); let x = ["Ferris", "Bueller's", "Day", "Off"]; let y = x.map(|v| v.len()); assert_eq!(y, [6, 9, 3, 3]);Run
pub fn zip<U>(self, rhs: [U; N]) -> [(T, U); N]
[src]
‘Zips up’ two arrays into a single array of pairs.
zip()
returns a new array where every element is a tuple where the
first element comes from the first array, and the second element comes
from the second array. In other words, it zips two arrays together,
into a single one.
Examples
#![feature(array_zip)] let x = [1, 2, 3]; let y = [4, 5, 6]; let z = x.zip(y); assert_eq!(z, [(1, 4), (2, 5), (3, 6)]);Run
pub fn as_slice(&self) -> &[T]ⓘ
[src]
Returns a slice containing the entire array. Equivalent to &s[..]
.
pub fn as_mut_slice(&mut self) -> &mut [T]ⓘ
[src]
Returns a mutable slice containing the entire array. Equivalent to
&mut s[..]
.
pub fn each_ref(&self) -> [&T; N]
[src]
Borrows each element and returns an array of references with the same
size as self
.
Example
#![feature(array_methods)] let floats = [3.1, 2.7, -1.0]; let float_refs: [&f64; 3] = floats.each_ref(); assert_eq!(float_refs, [&3.1, &2.7, &-1.0]);Run
This method is particularly useful if combined with other methods, like
map
. This way, you can avoid moving the original
array if its elements are not Copy
.
#![feature(array_methods, array_map)] let strings = ["Ferris".to_string(), "♥".to_string(), "Rust".to_string()]; let is_ascii = strings.each_ref().map(|s| s.is_ascii()); assert_eq!(is_ascii, [true, false, true]); // We can still access the original array: it has not been moved. assert_eq!(strings.len(), 3);Run
pub fn each_mut(&mut self) -> [&mut T; N]
[src]
Borrows each element mutably and returns an array of mutable references
with the same size as self
.
Example
#![feature(array_methods)] let mut floats = [3.1, 2.7, -1.0]; let float_refs: [&mut f64; 3] = floats.each_mut(); *float_refs[0] = 0.0; assert_eq!(float_refs, [&mut 0.0, &mut 2.7, &mut -1.0]); assert_eq!(floats, [0.0, 2.7, -1.0]);Run
Trait Implementations
impl<T, const N: usize> IntoIterator for [T; N]
1.53.0[src]
impl<T, const N: usize> IntoIterator for [T; N]
1.53.0[src]type Item = T
The type of the elements being iterated over.
type IntoIter = IntoIter<T, N>
Which kind of iterator are we turning this into?
pub fn into_iter(self) -> <[T; N] as IntoIterator>::IntoIter
[src]
Creates a consuming iterator, that is, one that moves each value out of
the array (from start to end). The array cannot be used after calling
this unless T
implements Copy
, so the whole array is copied.
Arrays have special behavior when calling .into_iter()
prior to the
2021 edition – see the array Editions section for more information.
impl<'a, T, const N: usize> IntoIterator for &'a [T; N]
[src]
impl<'a, T, const N: usize> IntoIterator for &'a [T; N]
[src]impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N]
[src]
impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N]
[src]impl<T, const N: usize> Ord for [T; N] where
T: Ord,
[src]
impl<T, const N: usize> Ord for [T; N] where
T: Ord,
[src]Implements comparison of arrays lexicographically.
impl<T, const N: usize> PartialOrd<[T; N]> for [T; N] where
T: PartialOrd<T>,
[src]
impl<T, const N: usize> PartialOrd<[T; N]> for [T; N] where
T: PartialOrd<T>,
[src]impl<T, const N: usize> SlicePattern for [T; N]
1.51.0[src]
impl<T, const N: usize> SlicePattern for [T; N]
1.51.0[src]impl<'_, T, const N: usize> TryFrom<&'_ [T]> for [T; N] where
T: Copy,
1.34.0[src]
impl<'_, T, const N: usize> TryFrom<&'_ [T]> for [T; N] where
T: Copy,
1.34.0[src]type Error = TryFromSliceError
The type returned in the event of a conversion error.
pub fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError>
[src]
impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N]
1.34.0[src]
impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N]
1.34.0[src]type Error = TryFromSliceError
The type returned in the event of a conversion error.
pub fn try_from(slice: &[T]) -> Result<&[T; N], TryFromSliceError>
[src]
impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N]
1.34.0[src]
impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N]
1.34.0[src]type Error = TryFromSliceError
The type returned in the event of a conversion error.
pub fn try_from(slice: &mut [T]) -> Result<&mut [T; N], TryFromSliceError>
[src]
impl<T, A, const N: usize> TryFrom<Vec<T, A>> for [T; N] where
A: Allocator,
1.48.0[src]
impl<T, A, const N: usize> TryFrom<Vec<T, A>> for [T; N] where
A: Allocator,
1.48.0[src]type Error = Vec<T, A>
The type returned in the event of a conversion error.
pub fn try_from(vec: Vec<T, A>) -> Result<[T; N], Vec<T, A>>
[src]
Gets the entire contents of the Vec<T>
as an array,
if its size exactly matches that of the requested array.
Examples
use std::convert::TryInto; assert_eq!(vec![1, 2, 3].try_into(), Ok([1, 2, 3])); assert_eq!(<Vec<i32>>::new().try_into(), Ok([]));Run
If the length doesn’t match, the input comes back in Err
:
use std::convert::TryInto; let r: Result<[i32; 4], _> = (0..10).collect::<Vec<_>>().try_into(); assert_eq!(r, Err(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9]));Run
If you’re fine with just getting a prefix of the Vec<T>
,
you can call .truncate(N)
first.
use std::convert::TryInto; let mut v = String::from("hello world").into_bytes(); v.sort(); v.truncate(2); let [a, b]: [_; 2] = v.try_into().unwrap(); assert_eq!(a, b' '); assert_eq!(b, b'd');Run
impl<T, const N: usize> Eq for [T; N] where
T: Eq,
[src]
T: Eq,
Auto Trait Implementations
impl<T, const N: usize> RefUnwindSafe for [T; N] where
T: RefUnwindSafe,
T: RefUnwindSafe,
impl<T, const N: usize> Send for [T; N] where
T: Send,
T: Send,
impl<T, const N: usize> Sync for [T; N] where
T: Sync,
T: Sync,
impl<T, const N: usize> Unpin for [T; N] where
T: Unpin,
T: Unpin,
impl<T, const N: usize> UnwindSafe for [T; N] where
T: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
impl<T> Borrow<T> for T where
T: ?Sized,
[src]
impl<T> Borrow<T> for T where
T: ?Sized,
[src]pub fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]pub fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]
Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W