Primitive Type array

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 [expr; N] where N is how many times to repeat expr in the array. expr must either be:

  • A value of a type implementing the Copy trait
  • A const value

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 of sizes from 1 to 12 (inclusive) implement From<Tuple>, where Tuple is a homogeneous tuple of appropriate length.

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. Instead, use slice.try_into().unwrap() or <ArrayType>::try_from(slice).unwrap().

Array’s try_from(slice) implementations (and the corresponding slice.try_into() array implementations) succeed if the input slice length is the same as the result array length. They optimize especially well when the optimizer can easily determine the slice length, e.g. <[u8; 4]>::try_from(&slice[4..8]).unwrap(). Array implements TryFrom returning:

• [T; N] copies from the slice’s elements
• &[T; N] references the original slice’s elements
• &mut [T; N] references the original slice’s elements

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} ");
}

You can also iterate over reference to the array’s elements:

let array: [i32; 3] = [0; 3];

for x in &array { }

You can use <ArrayType>::try_from(slice) or slice.try_into() to get an array from a slice:

let bytes: [u8; 3] = [1, 0, 2];
assert_eq!(1, u16::from_le_bytes(<[u8; 2]>::try_from(&bytes[0..2]).unwrap()));
assert_eq!(512, u16::from_le_bytes(bytes[1..3].try_into().unwrap()));

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);

Arrays can be created from homogeneous tuples of appropriate length:

let tuple: (u32, u32, u32) = (1, 2, 3);
let array: [u32; 3] = tuple.into();

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.

// Rust 2015 and 2018:

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`
for item in IntoIterator::into_iter(array).enumerate() {
    let (i, x): (usize, i32) = item;
    println!("array[{i}] = {x}");
}

Starting in the 2021 edition, array.into_iter() uses IntoIterator normally to iterate by value, and iter() should be used to iterate by reference like previous editions.

// Rust 2021:

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}");
}

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 IntoIterator::into_iter, equivalent to the post-2021 behavior (Rust 1.53+)
• replace for ... in array.into_iter() { with for ... in array {, equivalent to the post-2021 behavior (Rust 1.53+)

// Rust 2015 and 2018:

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 IntoIterator::into_iter(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 IntoIterator::into_iter(array).enumerate() {
    let (i, x): (usize, i32) = item;
    println!("array[{i}] = {x}");
}

Implementations

impl<T, const N: usize> [MaybeUninit<T>; N]

pub const fn transpose(self) -> MaybeUninit<[T; N]>

🔬This is a nightly-only experimental API. (maybe_uninit_uninit_array_transpose #96097)

Transposes a [MaybeUninit<T>; N] into a MaybeUninit<[T; N]>.

Examples

#![feature(maybe_uninit_uninit_array_transpose)]

let data = [MaybeUninit::<u8>::uninit(); 1000];
let data: MaybeUninit<[u8; 1000]> = data.transpose();

impl<const N: usize> [u8; N]

pub const fn as_ascii(&self) -> Option<&[AsciiChar; N]>

🔬This is a nightly-only experimental API. (ascii_char #110998)

Converts this array of bytes into an array of ASCII characters, or returns None if any of the characters is non-ASCII.

Examples

#![feature(ascii_char)]

const HEX_DIGITS: [std::ascii::Char; 16] =
    *b"0123456789abcdef".as_ascii().unwrap();

assert_eq!(HEX_DIGITS[1].as_str(), "1");
assert_eq!(HEX_DIGITS[10].as_str(), "a");

pub const unsafe fn as_ascii_unchecked(&self) -> &[AsciiChar; N]

🔬This is a nightly-only experimental API. (ascii_char #110998)

Converts this array of bytes into an array of ASCII characters, without checking whether they’re valid.

Safety

Every byte in the array must be in 0..=127, or else this is UB.

impl<T, const N: usize> [T; N]

pub fn map<F, U>(self, f: F) -> [U; N]

where F: FnMut(T) -> U,

Returns an array of the same size as self, with function f applied to each element in order.

If you don’t necessarily need a new fixed-size array, consider using Iterator::map instead.

Note on performance and stack usage

Unfortunately, usages of this method are currently not always optimized as well as they could be. This mainly concerns large arrays, as mapping over small arrays seem to be optimized just fine. Also note that in debug mode (i.e. without any optimizations), this method can use a lot of stack space (a few times the size of the array or more).

Therefore, in performance-critical code, try to avoid using this method on large arrays or check the emitted code. Also try to avoid chained maps (e.g. arr.map(...).map(...)).

In many cases, you can instead use Iterator::map by calling .iter() or .into_iter() on your array. [T; N]::map is only necessary if you really need a new array of the same size as the result. Rust’s lazy iterators tend to get optimized very well.

Examples

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]);

pub fn try_map<R>( self, f: impl FnMut(T) -> R, ) -> <<R as Try>::Residual as Residual<[<R as Try>::Output; N]>>::TryType

where R: Try, <R as Try>::Residual: Residual<[<R as Try>::Output; N]>,

🔬This is a nightly-only experimental API. (array_try_map #79711)

A fallible function f applied to each element on array self in order to return an array the same size as self or the first error encountered.

The return type of this function depends on the return type of the closure. If you return Result<T, E> from the closure, you’ll get a Result<[T; N], E>. If you return Option<T> from the closure, you’ll get an Option<[T; N]>.

Examples

#![feature(array_try_map)]

let a = ["1", "2", "3"];
let b = a.try_map(|v| v.parse::<u32>()).unwrap().map(|v| v + 1);
assert_eq!(b, [2, 3, 4]);

let a = ["1", "2a", "3"];
let b = a.try_map(|v| v.parse::<u32>());
assert!(b.is_err());

use std::num::NonZero;

let z = [1, 2, 0, 3, 4];
assert_eq!(z.try_map(NonZero::new), None);

let a = [1, 2, 3];
let b = a.try_map(NonZero::new);
let c = b.map(|x| x.map(NonZero::get));
assert_eq!(c, Some(a));

pub const fn as_slice(&self) -> &[T]

Returns a slice containing the entire array. Equivalent to &s[..].

pub fn as_mut_slice(&mut self) -> &mut [T]

Returns a mutable slice containing the entire array. Equivalent to &mut s[..].

pub fn each_ref(&self) -> [&T; N]

Borrows each element and returns an array of references with the same size as self.

Example

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]);

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.

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);

pub fn each_mut(&mut self) -> [&mut T; N]

Borrows each element mutably and returns an array of mutable references with the same size as self.

Example

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]);

pub fn split_array_ref<const M: usize>(&self) -> (&[T; M], &[T])

🔬This is a nightly-only experimental API. (split_array #90091)

Divides one array reference into two at an index.

The first will contain all indices from [0, M) (excluding the index M itself) and the second will contain all indices from [M, N) (excluding the index N itself).

Panics

Panics if M > N.

Examples

#![feature(split_array)]

let v = [1, 2, 3, 4, 5, 6];

{
   let (left, right) = v.split_array_ref::<0>();
   assert_eq!(left, &[]);
   assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
}

{
    let (left, right) = v.split_array_ref::<2>();
    assert_eq!(left, &[1, 2]);
    assert_eq!(right, &[3, 4, 5, 6]);
}

{
    let (left, right) = v.split_array_ref::<6>();
    assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
    assert_eq!(right, &[]);
}

pub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T])

🔬This is a nightly-only experimental API. (split_array #90091)

Divides one mutable array reference into two at an index.

The first will contain all indices from [0, M) (excluding the index M itself) and the second will contain all indices from [M, N) (excluding the index N itself).

Panics

Panics if M > N.

Examples

#![feature(split_array)]

let mut v = [1, 0, 3, 0, 5, 6];
let (left, right) = v.split_array_mut::<2>();
assert_eq!(left, &mut [1, 0][..]);
assert_eq!(right, &mut [3, 0, 5, 6]);
left[1] = 2;
right[1] = 4;
assert_eq!(v, [1, 2, 3, 4, 5, 6]);

pub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M])

🔬This is a nightly-only experimental API. (split_array #90091)

Divides one array reference into two at an index from the end.

The first will contain all indices from [0, N - M) (excluding the index N - M itself) and the second will contain all indices from [N - M, N) (excluding the index N itself).

Panics

Panics if M > N.

Examples

#![feature(split_array)]

let v = [1, 2, 3, 4, 5, 6];

{
   let (left, right) = v.rsplit_array_ref::<0>();
   assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
   assert_eq!(right, &[]);
}

{
    let (left, right) = v.rsplit_array_ref::<2>();
    assert_eq!(left, &[1, 2, 3, 4]);
    assert_eq!(right, &[5, 6]);
}

{
    let (left, right) = v.rsplit_array_ref::<6>();
    assert_eq!(left, &[]);
    assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
}

pub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M])

🔬This is a nightly-only experimental API. (split_array #90091)

Divides one mutable array reference into two at an index from the end.

The first will contain all indices from [0, N - M) (excluding the index N - M itself) and the second will contain all indices from [N - M, N) (excluding the index N itself).

Panics

Panics if M > N.

Examples

#![feature(split_array)]

let mut v = [1, 0, 3, 0, 5, 6];
let (left, right) = v.rsplit_array_mut::<4>();
assert_eq!(left, &mut [1, 0]);
assert_eq!(right, &mut [3, 0, 5, 6][..]);
left[1] = 2;
right[1] = 4;
assert_eq!(v, [1, 2, 3, 4, 5, 6]);

impl<T, const N: usize> [Option<T>; N]

pub fn transpose(self) -> Option<[T; N]>

🔬This is a nightly-only experimental API. (option_array_transpose #130828)

Transposes a [Option<T>; N] into a Option<[T; N]>.

Examples

#![feature(option_array_transpose)]

let data = [Some(0); 1000];
let data: Option<[u8; 1000]> = data.transpose();
assert_eq!(data, Some([0; 1000]));

let data = [Some(0), None];
let data: Option<[u8; 2]> = data.transpose();
assert_eq!(data, None);

Trait Implementations

impl<T, const N: usize> AsMut<[T]> for [T; N]

fn as_mut(&mut self) -> &mut [T]

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T, const N: usize> AsMut<[T; N]> for Simd<T, N>

where LaneCount<N>: SupportedLaneCount, T: SimdElement,

fn as_mut(&mut self) -> &mut [T; N]

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T, const N: usize> AsRef<[T]> for [T; N]

fn as_ref(&self) -> &[T]

Converts this type into a shared reference of the (usually inferred) input type.

impl<T, const N: usize> AsRef<[T; N]> for Simd<T, N>

where LaneCount<N>: SupportedLaneCount, T: SimdElement,

fn as_ref(&self) -> &[T; N]

Converts this type into a shared reference of the (usually inferred) input type.

impl<T, const N: usize> Borrow<[T]> for [T; N]

fn borrow(&self) -> &[T]

Immutably borrows from an owned value.

impl<T, const N: usize> BorrowMut<[T]> for [T; N]

fn borrow_mut(&mut self) -> &mut [T]

Mutably borrows from an owned value.

impl<T, const N: usize> Clone for [T; N]

where T: Clone,

fn clone(&self) -> [T; N]

Returns a copy of the value.

fn clone_from(&mut self, other: &[T; N])

Performs copy-assignment from source.

impl<T, const N: usize> Debug for [T; N]

where T: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> Default for [T; 32]

where T: Default,

fn default() -> [T; 32]

Returns the “default value” for a type.

impl<T> Default for [T; 31]

where T: Default,

fn default() -> [T; 31]

Returns the “default value” for a type.

impl<T> Default for [T; 30]

where T: Default,

fn default() -> [T; 30]

Returns the “default value” for a type.

impl<T> Default for [T; 29]

where T: Default,

fn default() -> [T; 29]

Returns the “default value” for a type.

impl<T> Default for [T; 28]

where T: Default,

fn default() -> [T; 28]

Returns the “default value” for a type.

impl<T> Default for [T; 27]

where T: Default,

fn default() -> [T; 27]

Returns the “default value” for a type.

impl<T> Default for [T; 26]

where T: Default,

fn default() -> [T; 26]

Returns the “default value” for a type.

impl<T> Default for [T; 25]

where T: Default,

fn default() -> [T; 25]

Returns the “default value” for a type.

impl<T> Default for [T; 24]

where T: Default,

fn default() -> [T; 24]

Returns the “default value” for a type.

impl<T> Default for [T; 23]

where T: Default,

fn default() -> [T; 23]

Returns the “default value” for a type.

impl<T> Default for [T; 22]

where T: Default,

fn default() -> [T; 22]

Returns the “default value” for a type.

impl<T> Default for [T; 21]

where T: Default,

fn default() -> [T; 21]

Returns the “default value” for a type.

impl<T> Default for [T; 20]

where T: Default,

fn default() -> [T; 20]

Returns the “default value” for a type.

impl<T> Default for [T; 19]

where T: Default,

fn default() -> [T; 19]

Returns the “default value” for a type.

impl<T> Default for [T; 18]

where T: Default,

fn default() -> [T; 18]

Returns the “default value” for a type.

impl<T> Default for [T; 17]

where T: Default,

fn default() -> [T; 17]

Returns the “default value” for a type.

impl<T> Default for [T; 16]

where T: Default,

fn default() -> [T; 16]

Returns the “default value” for a type.

impl<T> Default for [T; 15]

where T: Default,

fn default() -> [T; 15]

Returns the “default value” for a type.

impl<T> Default for [T; 14]

where T: Default,

fn default() -> [T; 14]

Returns the “default value” for a type.

impl<T> Default for [T; 13]

where T: Default,

fn default() -> [T; 13]

Returns the “default value” for a type.

impl<T> Default for [T; 12]

where T: Default,

fn default() -> [T; 12]

Returns the “default value” for a type.

impl<T> Default for [T; 11]

where T: Default,

fn default() -> [T; 11]

Returns the “default value” for a type.

impl<T> Default for [T; 10]

where T: Default,

fn default() -> [T; 10]

Returns the “default value” for a type.

impl<T> Default for [T; 9]

where T: Default,

fn default() -> [T; 9]

Returns the “default value” for a type.

impl<T> Default for [T; 8]

where T: Default,

fn default() -> [T; 8]

Returns the “default value” for a type.

impl<T> Default for [T; 7]

where T: Default,

fn default() -> [T; 7]

Returns the “default value” for a type.

impl<T> Default for [T; 6]

where T: Default,

fn default() -> [T; 6]

Returns the “default value” for a type.

impl<T> Default for [T; 5]

where T: Default,

fn default() -> [T; 5]

Returns the “default value” for a type.

impl<T> Default for [T; 4]

where T: Default,

fn default() -> [T; 4]

Returns the “default value” for a type.

impl<T> Default for [T; 3]

where T: Default,

fn default() -> [T; 3]

Returns the “default value” for a type.

impl<T> Default for [T; 2]

where T: Default,

fn default() -> [T; 2]

Returns the “default value” for a type.

impl<T> Default for [T; 1]

where T: Default,

fn default() -> [T; 1]

Returns the “default value” for a type.

impl<T> Default for [T; 0]

fn default() -> [T; 0]

Returns the “default value” for a type.

impl<'a, T, const N: usize> From<&'a [T; N]> for Cow<'a, [T]>

where T: Clone,

fn from(s: &'a [T; N]) -> Cow<'a, [T]>

Creates a Borrowed variant of Cow from a reference to an array.

This conversion does not allocate or clone the data.

impl<T, const N: usize> From<&[T; N]> for Vec<T>

where T: Clone,

fn from(s: &[T; N]) -> Vec<T>

Allocates a Vec<T> and fills it by cloning s’s items.

Examples

assert_eq!(Vec::from(&[1, 2, 3]), vec![1, 2, 3]);

impl<T, const N: usize> From<&mut [T; N]> for Vec<T>

where T: Clone,

fn from(s: &mut [T; N]) -> Vec<T>

Allocates a Vec<T> and fills it by cloning s’s items.

Examples

assert_eq!(Vec::from(&mut [1, 2, 3]), vec![1, 2, 3]);

impl<K, V, const N: usize> From<[(K, V); N]> for BTreeMap<K, V>

where K: Ord,

fn from(arr: [(K, V); N]) -> BTreeMap<K, V>

Converts a [(K, V); N] into a BTreeMap<(K, V)>.

use std::collections::BTreeMap;

let map1 = BTreeMap::from([(1, 2), (3, 4)]);
let map2: BTreeMap<_, _> = [(1, 2), (3, 4)].into();
assert_eq!(map1, map2);

impl<K, V, const N: usize> From<[(K, V); N]> for HashMap<K, V, RandomState>

where K: Eq + Hash,

fn from(arr: [(K, V); N]) -> Self

Examples

use std::collections::HashMap;

let map1 = HashMap::from([(1, 2), (3, 4)]);
let map2: HashMap<_, _> = [(1, 2), (3, 4)].into();
assert_eq!(map1, map2);

impl<T> From<[T; N]> for (T₁, T₂, …, Tₙ)

This trait is implemented for tuples up to twelve items long.

fn from(array: [T; 1]) -> (T,)

Converts to this type from the input type.

impl<T, const N: usize> From<[T; N]> for Arc<[T]>

fn from(v: [T; N]) -> Arc<[T]>

Converts a [T; N] into an Arc<[T]>.

The conversion moves the array into a newly allocated Arc.

Example

let original: [i32; 3] = [1, 2, 3];
let shared: Arc<[i32]> = Arc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<T, const N: usize> From<[T; N]> for BTreeSet<T>

where T: Ord,

fn from(arr: [T; N]) -> BTreeSet<T>

Converts a [T; N] into a BTreeSet<T>.

use std::collections::BTreeSet;

let set1 = BTreeSet::from([1, 2, 3, 4]);
let set2: BTreeSet<_> = [1, 2, 3, 4].into();
assert_eq!(set1, set2);

impl<T, const N: usize> From<[T; N]> for BinaryHeap<T>

where T: Ord,

fn from(arr: [T; N]) -> BinaryHeap<T>

use std::collections::BinaryHeap;

let mut h1 = BinaryHeap::from([1, 4, 2, 3]);
let mut h2: BinaryHeap<_> = [1, 4, 2, 3].into();
while let Some((a, b)) = h1.pop().zip(h2.pop()) {
    assert_eq!(a, b);
}

impl<T, const N: usize> From<[T; N]> for Box<[T]>

fn from(array: [T; N]) -> Box<[T]>

Converts a [T; N] into a Box<[T]>

This conversion moves the array to newly heap-allocated memory.

Examples

let boxed: Box<[u8]> = Box::from([4, 2]);
println!("{boxed:?}");

impl<T, const N: usize> From<[T; N]> for HashSet<T, RandomState>

where T: Eq + Hash,

fn from(arr: [T; N]) -> Self

Examples

use std::collections::HashSet;

let set1 = HashSet::from([1, 2, 3, 4]);
let set2: HashSet<_> = [1, 2, 3, 4].into();
assert_eq!(set1, set2);

impl<T, const N: usize> From<[T; N]> for LinkedList<T>

fn from(arr: [T; N]) -> LinkedList<T>

Converts a [T; N] into a LinkedList<T>.

use std::collections::LinkedList;

let list1 = LinkedList::from([1, 2, 3, 4]);
let list2: LinkedList<_> = [1, 2, 3, 4].into();
assert_eq!(list1, list2);

impl<T, const N: usize> From<[T; N]> for Rc<[T]>

fn from(v: [T; N]) -> Rc<[T]>

Converts a [T; N] into an Rc<[T]>.

The conversion moves the array into a newly allocated Rc.

Example

let original: [i32; 3] = [1, 2, 3];
let shared: Rc<[i32]> = Rc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<T, const N: usize> From<[T; N]> for Simd<T, N>

where LaneCount<N>: SupportedLaneCount, T: SimdElement,

fn from(array: [T; N]) -> Simd<T, N>

Converts to this type from the input type.

impl<T, const N: usize> From<[T; N]> for Vec<T>

fn from(s: [T; N]) -> Vec<T>

Allocates a Vec<T> and moves s’s items into it.

Examples

assert_eq!(Vec::from([1, 2, 3]), vec![1, 2, 3]);

impl<T, const N: usize> From<[T; N]> for VecDeque<T>

fn from(arr: [T; N]) -> VecDeque<T>

Converts a [T; N] into a VecDeque<T>.

use std::collections::VecDeque;

let deq1 = VecDeque::from([1, 2, 3, 4]);
let deq2: VecDeque<_> = [1, 2, 3, 4].into();
assert_eq!(deq1, deq2);

impl<T, const N: usize> From<[bool; N]> for Mask<T, N>

where T: MaskElement, LaneCount<N>: SupportedLaneCount,

fn from(array: [bool; N]) -> Mask<T, N>

Converts to this type from the input type.

impl From<[u16; 8]> for IpAddr

fn from(segments: [u16; 8]) -> IpAddr

Creates an IpAddr::V6 from an eight element 16-bit array.

Examples

use std::net::{IpAddr, Ipv6Addr};

let addr = IpAddr::from([
    0x20du16, 0x20cu16, 0x20bu16, 0x20au16,
    0x209u16, 0x208u16, 0x207u16, 0x206u16,
]);
assert_eq!(
    IpAddr::V6(Ipv6Addr::new(
        0x20d, 0x20c, 0x20b, 0x20a,
        0x209, 0x208, 0x207, 0x206,
    )),
    addr
);

impl From<[u16; 8]> for Ipv6Addr

fn from(segments: [u16; 8]) -> Ipv6Addr

Creates an Ipv6Addr from an eight element 16-bit array.

Examples

use std::net::Ipv6Addr;

let addr = Ipv6Addr::from([
    0x20du16, 0x20cu16, 0x20bu16, 0x20au16,
    0x209u16, 0x208u16, 0x207u16, 0x206u16,
]);
assert_eq!(
    Ipv6Addr::new(
        0x20d, 0x20c, 0x20b, 0x20a,
        0x209, 0x208, 0x207, 0x206,
    ),
    addr
);

impl From<[u8; 16]> for IpAddr

fn from(octets: [u8; 16]) -> IpAddr

Creates an IpAddr::V6 from a sixteen element byte array.

Examples

use std::net::{IpAddr, Ipv6Addr};

let addr = IpAddr::from([
    0x19u8, 0x18u8, 0x17u8, 0x16u8, 0x15u8, 0x14u8, 0x13u8, 0x12u8,
    0x11u8, 0x10u8, 0x0fu8, 0x0eu8, 0x0du8, 0x0cu8, 0x0bu8, 0x0au8,
]);
assert_eq!(
    IpAddr::V6(Ipv6Addr::new(
        0x1918, 0x1716, 0x1514, 0x1312,
        0x1110, 0x0f0e, 0x0d0c, 0x0b0a,
    )),
    addr
);

impl From<[u8; 16]> for Ipv6Addr

fn from(octets: [u8; 16]) -> Ipv6Addr

Creates an Ipv6Addr from a sixteen element byte array.

Examples

use std::net::Ipv6Addr;

let addr = Ipv6Addr::from([
    0x19u8, 0x18u8, 0x17u8, 0x16u8, 0x15u8, 0x14u8, 0x13u8, 0x12u8,
    0x11u8, 0x10u8, 0x0fu8, 0x0eu8, 0x0du8, 0x0cu8, 0x0bu8, 0x0au8,
]);
assert_eq!(
    Ipv6Addr::new(
        0x1918, 0x1716, 0x1514, 0x1312,
        0x1110, 0x0f0e, 0x0d0c, 0x0b0a,
    ),
    addr
);

impl From<[u8; 4]> for IpAddr

fn from(octets: [u8; 4]) -> IpAddr

Creates an IpAddr::V4 from a four element byte array.

Examples

use std::net::{IpAddr, Ipv4Addr};

let addr = IpAddr::from([13u8, 12u8, 11u8, 10u8]);
assert_eq!(IpAddr::V4(Ipv4Addr::new(13, 12, 11, 10)), addr);

impl From<[u8; 4]> for Ipv4Addr

fn from(octets: [u8; 4]) -> Ipv4Addr

Creates an Ipv4Addr from a four element byte array.

Examples

use std::net::Ipv4Addr;

let addr = Ipv4Addr::from([13u8, 12u8, 11u8, 10u8]);
assert_eq!(Ipv4Addr::new(13, 12, 11, 10), addr);

impl<T> From<(T₁, T₂, …, Tₙ)> for [T; N]

This trait is implemented for tuples up to twelve items long.

fn from(tuple: (T,)) -> [T; 1]

Converts to this type from the input type.

impl<T, const N: usize> From<Mask<T, N>> for [bool; N]

where T: MaskElement, LaneCount<N>: SupportedLaneCount,

fn from(vector: Mask<T, N>) -> [bool; N]

Converts to this type from the input type.

impl<T, const N: usize> From<Simd<T, N>> for [T; N]

where LaneCount<N>: SupportedLaneCount, T: SimdElement,

fn from(vector: Simd<T, N>) -> [T; N]

Converts to this type from the input type.

impl<T, const N: usize> Hash for [T; N]

where T: Hash,

The hash of an array is the same as that of the corresponding slice, as required by the Borrow implementation.

use std::hash::BuildHasher;

let b = std::hash::RandomState::new();
let a: [u8; 3] = [0xa8, 0x3c, 0x09];
let s: &[u8] = &[0xa8, 0x3c, 0x09];
assert_eq!(b.hash_one(a), b.hash_one(s));

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T, I, const N: usize> Index<I> for [T; N]

where [T]: Index<I>,

type Output = <[T] as Index<I>>::Output

The returned type after indexing.

fn index(&self, index: I) -> &<[T; N] as Index<I>>::Output

Performs the indexing (container[index]) operation.

impl<T, I, const N: usize> IndexMut<I> for [T; N]

where [T]: IndexMut<I>,

fn index_mut(&mut self, index: I) -> &mut <[T; N] as Index<I>>::Output

Performs the mutable indexing (container[index]) operation.

impl<'a, T, const N: usize> IntoIterator for &'a [T; N]

type Item = &'a T

The type of the elements being iterated over.

type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Iter<'a, T>

Creates an iterator from a value.

impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N]

type Item = &'a mut T

The type of the elements being iterated over.

type IntoIter = IterMut<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> IterMut<'a, T>

Creates an iterator from a value.

impl<T, const N: usize> IntoIterator for [T; N]

fn into_iter(self) -> <[T; N] as IntoIterator>::IntoIter

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.

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?

impl<T, const N: usize> Ord for [T; N]

where T: Ord,

Implements comparison of arrays lexicographically.

fn cmp(&self, other: &[T; N]) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T, U, const N: usize> PartialEq<&[U]> for [T; N]

where T: PartialEq<U>,

fn eq(&self, other: &&[U]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&[U]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, A, const N: usize> PartialEq<&[U; N]> for Vec<T, A>

where A: Allocator, T: PartialEq<U>,

fn eq(&self, other: &&[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&[U; N]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, A, const N: usize> PartialEq<&[U; N]> for VecDeque<T, A>

where A: Allocator, T: PartialEq<U>,

fn eq(&self, other: &&[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, const N: usize> PartialEq<&mut [U]> for [T; N]

where T: PartialEq<U>,

fn eq(&self, other: &&mut [U]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &&mut [U]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, A, const N: usize> PartialEq<&mut [U; N]> for VecDeque<T, A>

where A: Allocator, T: PartialEq<U>,

fn eq(&self, other: &&mut [U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, const N: usize> PartialEq<[U]> for [T; N]

where T: PartialEq<U>,

fn eq(&self, other: &[U]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &[U]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, const N: usize> PartialEq<[U; N]> for &[T]

where T: PartialEq<U>,

fn eq(&self, other: &[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &[U; N]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, const N: usize> PartialEq<[U; N]> for &mut [T]

where T: PartialEq<U>,

fn eq(&self, other: &[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &[U; N]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, const N: usize> PartialEq<[U; N]> for [T]

where T: PartialEq<U>,

fn eq(&self, other: &[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &[U; N]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, const N: usize> PartialEq<[U; N]> for [T; N]

where T: PartialEq<U>,

fn eq(&self, other: &[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &[U; N]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, A, const N: usize> PartialEq<[U; N]> for Vec<T, A>

where A: Allocator, T: PartialEq<U>,

fn eq(&self, other: &[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &[U; N]) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U, A, const N: usize> PartialEq<[U; N]> for VecDeque<T, A>

where A: Allocator, T: PartialEq<U>,

fn eq(&self, other: &[U; N]) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, const N: usize> PartialOrd for [T; N]

where T: PartialOrd,

Implements comparison of arrays lexicographically.

fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &[T; N]) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &[T; N]) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn ge(&self, other: &[T; N]) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

fn gt(&self, other: &[T; N]) -> bool

Tests greater than (for self and other) and is used by the > operator.

impl<'b, const N: usize> Pattern for &'b [char; N]

Searches for chars that are equal to any of the chars in the array.

Examples

assert_eq!("Hello world".find(&['o', 'l']), Some(2));
assert_eq!("Hello world".find(&['h', 'w']), Some(6));

type Searcher<'a> = CharArrayRefSearcher<'a, 'b, N>

🔬This is a nightly-only experimental API. (pattern #27721)

Associated searcher for this pattern

fn into_searcher<'a>(self, haystack: &'a str) -> CharArrayRefSearcher<'a, 'b, N>

🔬This is a nightly-only experimental API. (pattern #27721)

Constructs the associated searcher from self and the haystack to search in.

fn is_contained_in<'a>(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches anywhere in the haystack

fn is_prefix_of<'a>(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the front of the haystack

fn strip_prefix_of<'a>(self, haystack: &'a str) -> Option<&'a str>

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the front of haystack, if it matches.

fn is_suffix_of<'a>(self, haystack: &'a str) -> bool

where CharArrayRefSearcher<'a, 'b, N>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the back of the haystack

fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&'a str>

where CharArrayRefSearcher<'a, 'b, N>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the back of haystack, if it matches.

fn as_utf8_pattern(&self) -> Option<Utf8Pattern<'_>>

🔬This is a nightly-only experimental API. (pattern #27721)

Returns the pattern as utf-8 bytes if possible.

impl<const N: usize> Pattern for [char; N]

Searches for chars that are equal to any of the chars in the array.

Examples

assert_eq!("Hello world".find(['o', 'l']), Some(2));
assert_eq!("Hello world".find(['h', 'w']), Some(6));

type Searcher<'a> = CharArraySearcher<'a, N>

🔬This is a nightly-only experimental API. (pattern #27721)

Associated searcher for this pattern

fn into_searcher<'a>(self, haystack: &'a str) -> CharArraySearcher<'a, N>

🔬This is a nightly-only experimental API. (pattern #27721)

Constructs the associated searcher from self and the haystack to search in.

fn is_contained_in<'a>(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches anywhere in the haystack

fn is_prefix_of<'a>(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the front of the haystack

fn strip_prefix_of<'a>(self, haystack: &'a str) -> Option<&'a str>

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the front of haystack, if it matches.

fn is_suffix_of<'a>(self, haystack: &'a str) -> bool

where CharArraySearcher<'a, N>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the back of the haystack

fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&'a str>

where CharArraySearcher<'a, N>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the back of haystack, if it matches.

fn as_utf8_pattern(&self) -> Option<Utf8Pattern<'_>>

🔬This is a nightly-only experimental API. (pattern #27721)

Returns the pattern as utf-8 bytes if possible.

impl<T, const N: usize> SlicePattern for [T; N]

type Item = T

🔬This is a nightly-only experimental API. (slice_pattern #56345)

The element type of the slice being matched on.

fn as_slice(&self) -> &[<[T; N] as SlicePattern>::Item]

🔬This is a nightly-only experimental API. (slice_pattern #56345)

Currently, the consumers of SlicePattern need a slice.

impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N]

Tries to create an array ref &[T; N] from a slice ref &[T]. Succeeds if slice.len() == N.

let bytes: [u8; 3] = [1, 0, 2];

let bytes_head: &[u8; 2] = <&[u8; 2]>::try_from(&bytes[0..2]).unwrap();
assert_eq!(1, u16::from_le_bytes(*bytes_head));

let bytes_tail: &[u8; 2] = bytes[1..3].try_into().unwrap();
assert_eq!(512, u16::from_le_bytes(*bytes_tail));

type Error = TryFromSliceError

The type returned in the event of a conversion error.

fn try_from(slice: &'a [T]) -> Result<&'a [T; N], TryFromSliceError>

Performs the conversion.

impl<T, const N: usize> TryFrom<&[T]> for [T; N]

where T: Copy,

Tries to create an array [T; N] by copying from a slice &[T]. Succeeds if slice.len() == N.

let bytes: [u8; 3] = [1, 0, 2];

let bytes_head: [u8; 2] = <[u8; 2]>::try_from(&bytes[0..2]).unwrap();
assert_eq!(1, u16::from_le_bytes(bytes_head));

let bytes_tail: [u8; 2] = bytes[1..3].try_into().unwrap();
assert_eq!(512, u16::from_le_bytes(bytes_tail));

type Error = TryFromSliceError

The type returned in the event of a conversion error.

fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError>

Performs the conversion.

impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N]

Tries to create a mutable array ref &mut [T; N] from a mutable slice ref &mut [T]. Succeeds if slice.len() == N.

let mut bytes: [u8; 3] = [1, 0, 2];

let bytes_head: &mut [u8; 2] = <&mut [u8; 2]>::try_from(&mut bytes[0..2]).unwrap();
assert_eq!(1, u16::from_le_bytes(*bytes_head));

let bytes_tail: &mut [u8; 2] = (&mut bytes[1..3]).try_into().unwrap();
assert_eq!(512, u16::from_le_bytes(*bytes_tail));

type Error = TryFromSliceError

The type returned in the event of a conversion error.

fn try_from(slice: &'a mut [T]) -> Result<&'a mut [T; N], TryFromSliceError>

Performs the conversion.

impl<T, const N: usize> TryFrom<&mut [T]> for [T; N]

where T: Copy,

Tries to create an array [T; N] by copying from a mutable slice &mut [T]. Succeeds if slice.len() == N.

let mut bytes: [u8; 3] = [1, 0, 2];

let bytes_head: [u8; 2] = <[u8; 2]>::try_from(&mut bytes[0..2]).unwrap();
assert_eq!(1, u16::from_le_bytes(bytes_head));

let bytes_tail: [u8; 2] = (&mut bytes[1..3]).try_into().unwrap();
assert_eq!(512, u16::from_le_bytes(bytes_tail));

type Error = TryFromSliceError

The type returned in the event of a conversion error.

fn try_from(slice: &mut [T]) -> Result<[T; N], TryFromSliceError>

Performs the conversion.

impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]>

fn try_from( boxed_slice: Box<[T]>, ) -> Result<Box<[T; N]>, <Box<[T; N]> as TryFrom<Box<[T]>>>::Error>

Attempts to convert a Box<[T]> into a Box<[T; N]>.

The conversion occurs in-place and does not require a new memory allocation.

Errors

Returns the old Box<[T]> in the Err variant if boxed_slice.len() does not equal N.

type Error = Box<[T]>

The type returned in the event of a conversion error.

impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]>

fn try_from( vec: Vec<T>, ) -> Result<Box<[T; N]>, <Box<[T; N]> as TryFrom<Vec<T>>>::Error>

Attempts to convert a Vec<T> into a Box<[T; N]>.

Like Vec::into_boxed_slice, this is in-place if vec.capacity() == N, but will require a reallocation otherwise.

Errors

Returns the original Vec<T> in the Err variant if boxed_slice.len() does not equal N.

Examples

This can be used with vec! to create an array on the heap:

let state: Box<[f32; 100]> = vec![1.0; 100].try_into().unwrap();
assert_eq!(state.len(), 100);

type Error = Vec<T>

The type returned in the event of a conversion error.

impl<T, A, const N: usize> TryFrom<Vec<T, A>> for [T; N]

where A: Allocator,

fn try_from(vec: Vec<T, A>) -> Result<[T; N], Vec<T, A>>

Gets the entire contents of the Vec<T> as an array, if its size exactly matches that of the requested array.

Examples

assert_eq!(vec![1, 2, 3].try_into(), Ok([1, 2, 3]));
assert_eq!(<Vec<i32>>::new().try_into(), Ok([]));

If the length doesn’t match, the input comes back in Err:

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]));

If you’re fine with just getting a prefix of the Vec<T>, you can call .truncate(N) first.

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');

type Error = Vec<T, A>

The type returned in the event of a conversion error.

impl<T, const N: usize> ConstParamTy_ for [T; N]

where T: ConstParamTy_,

impl<T, const N: usize> Copy for [T; N]

where T: Copy,

impl<T, const N: usize> Eq for [T; N]

where T: Eq,

impl<T, const N: usize> StructuralPartialEq for [T; N]

impl<T, const N: usize> UnsizedConstParamTy for [T; N]

where T: UnsizedConstParamTy,