Struct std::vec::Vec [−] [src]

```pub struct Vec<T> {
// some fields omitted
}```
1.0.0

A contiguous growable array type, written `Vec<T>` but pronounced 'vector.'

Examples

fn main() { let mut vec = Vec::new(); vec.push(1); vec.push(2); assert_eq!(vec.len(), 2); assert_eq!(vec[0], 1); assert_eq!(vec.pop(), Some(2)); assert_eq!(vec.len(), 1); vec[0] = 7; assert_eq!(vec[0], 7); vec.extend([1, 2, 3].iter().cloned()); for x in &vec { println!("{}", x); } assert_eq!(vec, [7, 1, 2, 3]); }
```let mut vec = Vec::new();
vec.push(1);
vec.push(2);

assert_eq!(vec.len(), 2);
assert_eq!(vec[0], 1);

assert_eq!(vec.pop(), Some(2));
assert_eq!(vec.len(), 1);

vec[0] = 7;
assert_eq!(vec[0], 7);

vec.extend([1, 2, 3].iter().cloned());

for x in &vec {
println!("{}", x);
}
assert_eq!(vec, [7, 1, 2, 3]);```

The `vec!` macro is provided to make initialization more convenient:

fn main() { let mut vec = vec![1, 2, 3]; vec.push(4); assert_eq!(vec, [1, 2, 3, 4]); }
```let mut vec = vec![1, 2, 3];
vec.push(4);
assert_eq!(vec, [1, 2, 3, 4]);```

It can also initialize each element of a `Vec<T>` with a given value:

fn main() { let vec = vec![0; 5]; assert_eq!(vec, [0, 0, 0, 0, 0]); }
```let vec = vec![0; 5];
assert_eq!(vec, [0, 0, 0, 0, 0]);```

Use a `Vec<T>` as an efficient stack:

fn main() { let mut stack = Vec::new(); stack.push(1); stack.push(2); stack.push(3); while let Some(top) = stack.pop() { // Prints 3, 2, 1 println!("{}", top); } }
```let mut stack = Vec::new();

stack.push(1);
stack.push(2);
stack.push(3);

while let Some(top) = stack.pop() {
// Prints 3, 2, 1
println!("{}", top);
}```

Indexing

The Vec type allows to access values by index, because it implements the `Index` trait. An example will be more explicit:

fn main() { let v = vec!(0, 2, 4, 6); println!("{}", v[1]); // it will display '2' }
```let v = vec!(0, 2, 4, 6);
println!("{}", v[1]); // it will display '2'```

However be careful: if you try to access an index which isn't in the Vec, your software will panic! You cannot do this:

fn main() { let v = vec!(0, 2, 4, 6); println!("{}", v[6]); // it will panic! }
```let v = vec!(0, 2, 4, 6);
println!("{}", v[6]); // it will panic!```

In conclusion: always check if the index you want to get really exists before doing it.

Slicing

A Vec can be mutable. Slices, on the other hand, are read-only objects. To get a slice, use "&". Example:

fn main() { fn read_slice(slice: &[usize]) { // ... } let v = vec!(0, 1); read_slice(&v); // ... and that's all! // you can also do it like this: let x : &[usize] = &v; }
```fn read_slice(slice: &[usize]) {
// ...
}

let v = vec!(0, 1);

// ... and that's all!
// you can also do it like this:
let x : &[usize] = &v;```

In Rust, it's more common to pass slices as arguments rather than vectors when you just want to provide a read access. The same goes for String and &str.

Capacity and reallocation

The capacity of a vector is the amount of space allocated for any future elements that will be added onto the vector. This is not to be confused with the length of a vector, which specifies the number of actual elements within the vector. If a vector's length exceeds its capacity, its capacity will automatically be increased, but its elements will have to be reallocated.

For example, a vector with capacity 10 and length 0 would be an empty vector with space for 10 more elements. Pushing 10 or fewer elements onto the vector will not change its capacity or cause reallocation to occur. However, if the vector's length is increased to 11, it will have to reallocate, which can be slow. For this reason, it is recommended to use `Vec::with_capacity` whenever possible to specify how big the vector is expected to get.

Guarantees

Due to its incredibly fundamental nature, Vec makes a lot of guarantees about its design. This ensures that it's as low-overhead as possible in the general case, and can be correctly manipulated in primitive ways by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`. If additional type parameters are added (e.g. to support custom allocators), overriding their defaults may change the behavior.

Most fundamentally, Vec is and always will be a (pointer, capacity, length) triplet. No more, no less. The order of these fields is completely unspecified, and you should use the appropriate methods to modify these. The pointer will never be null, so this type is null-pointer-optimized.

However, the pointer may not actually point to allocated memory. In particular, if you construct a Vec with capacity 0 via `Vec::new()`, `vec![]`, `Vec::with_capacity(0)`, or by calling `shrink_to_fit()` on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized types inside a Vec, it will not allocate space for them. Note that in this case the Vec may not report a `capacity()` of 0. Vec will allocate if and only if `mem::size_of::<T>() * capacity() > 0`. In general, Vec's allocation details are subtle enough that it is strongly recommended that you only free memory allocated by a Vec by creating a new Vec and dropping it.

If a Vec has allocated memory, then the memory it points to is on the heap (as defined by the allocator Rust is configured to use by default), and its pointer points to `len()` initialized elements in order (what you would see if you coerced it to a slice), followed by `capacity() - len()` logically uninitialized elements.

Vec will never perform a "small optimization" where elements are actually stored on the stack for two reasons:

• It would make it more difficult for unsafe code to correctly manipulate a Vec. The contents of a Vec wouldn't have a stable address if it were only moved, and it would be more difficult to determine if a Vec had actually allocated memory.

• It would penalize the general case, incurring an additional branch on every access.

Vec will never automatically shrink itself, even if completely empty. This ensures no unnecessary allocations or deallocations occur. Emptying a Vec and then filling it back up to the same `len()` should incur no calls to the allocator. If you wish to free up unused memory, use `shrink_to_fit`.

`push` and `insert` will never (re)allocate if the reported capacity is sufficient. `push` and `insert` will (re)allocate if `len() == capacity()`. That is, the reported capacity is completely accurate, and can be relied on. It can even be used to manually free the memory allocated by a Vec if desired. Bulk insertion methods may reallocate, even when not necessary.

Vec does not guarantee any particular growth strategy when reallocating when full, nor when `reserve` is called. The current strategy is basic and it may prove desirable to use a non-constant growth factor. Whatever strategy is used will of course guarantee `O(1)` amortized `push`.

`vec![x; n]`, `vec![a, b, c, d]`, and `Vec::with_capacity(n)`, will all produce a Vec with exactly the requested capacity. If `len() == capacity()`, (as is the case for the `vec!` macro), then a `Vec<T>` can be converted to and from a `Box<[T]>` without reallocating or moving the elements.

Vec will not specifically overwrite any data that is removed from it, but also won't specifically preserve it. Its uninitialized memory is scratch space that it may use however it wants. It will generally just do whatever is most efficient or otherwise easy to implement. Do not rely on removed data to be erased for security purposes. Even if you drop a Vec, its buffer may simply be reused by another Vec. Even if you zero a Vec's memory first, that may not actually happen because the optimizer does not consider this a side-effect that must be preserved.

Vec does not currently guarantee the order in which elements are dropped (the order has changed in the past, and may change again).

Methods

`impl<T> Vec<T> where T: PartialEq<T>`

`fn dedup(&mut self)`

Removes consecutive repeated elements in the vector.

If the vector is sorted, this removes all duplicates.

Examples

fn main() { let mut vec = vec![1, 2, 2, 3, 2]; vec.dedup(); assert_eq!(vec, [1, 2, 3, 2]); }
```let mut vec = vec![1, 2, 2, 3, 2];

vec.dedup();

assert_eq!(vec, [1, 2, 3, 2]);```

`impl<T> Vec<T> where T: Clone`

1.5.0`fn resize(&mut self, new_len: usize, value: T)`

Resizes the `Vec` in-place so that `len()` is equal to `new_len`.

If `new_len` is greater than `len()`, the `Vec` is extended by the difference, with each additional slot filled with `value`. If `new_len` is less than `len()`, the `Vec` is simply truncated.

Examples

fn main() { let mut vec = vec!["hello"]; vec.resize(3, "world"); assert_eq!(vec, ["hello", "world", "world"]); let mut vec = vec![1, 2, 3, 4]; vec.resize(2, 0); assert_eq!(vec, [1, 2]); }
```let mut vec = vec!["hello"];
vec.resize(3, "world");
assert_eq!(vec, ["hello", "world", "world"]);

let mut vec = vec![1, 2, 3, 4];
vec.resize(2, 0);
assert_eq!(vec, [1, 2]);```

1.6.0`fn extend_from_slice(&mut self, other: &[T])`

Appends all elements in a slice to the `Vec`.

Iterates over the slice `other`, clones each element, and then appends it to this `Vec`. The `other` vector is traversed in-order.

Note that this function is same as `extend` except that it is specialized to work with slices instead. If and when Rust gets specialization this function will likely be deprecated (but still available).

Examples

fn main() { let mut vec = vec![1]; vec.extend_from_slice(&[2, 3, 4]); assert_eq!(vec, [1, 2, 3, 4]); }
```let mut vec = vec![1];
vec.extend_from_slice(&[2, 3, 4]);
assert_eq!(vec, [1, 2, 3, 4]);```

`impl<T> Vec<T>`

`fn new() -> Vec<T>`

Constructs a new, empty `Vec<T>`.

The vector will not allocate until elements are pushed onto it.

Examples

fn main() { #![allow(unused_mut)] let mut vec: Vec<i32> = Vec::new(); }
`let mut vec: Vec<i32> = Vec::new();`

`fn with_capacity(capacity: usize) -> Vec<T>`

Constructs a new, empty `Vec<T>` with the specified capacity.

The vector will be able to hold exactly `capacity` elements without reallocating. If `capacity` is 0, the vector will not allocate.

It is important to note that this function does not specify the length of the returned vector, but only the capacity. (For an explanation of the difference between length and capacity, see the main `Vec<T>` docs above, 'Capacity and reallocation'.)

Examples

fn main() { let mut vec = Vec::with_capacity(10); // The vector contains no items, even though it has capacity for more assert_eq!(vec.len(), 0); // These are all done without reallocating... for i in 0..10 { vec.push(i); } // ...but this may make the vector reallocate vec.push(11); }
```let mut vec = Vec::with_capacity(10);

// The vector contains no items, even though it has capacity for more
assert_eq!(vec.len(), 0);

// These are all done without reallocating...
for i in 0..10 {
vec.push(i);
}

// ...but this may make the vector reallocate
vec.push(11);```

`unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T>`

Creates a `Vec<T>` directly from the raw components of another vector.

Safety

This is highly unsafe, due to the number of invariants that aren't checked:

• `ptr` needs to have been previously allocated via `String`/`Vec<T>` (at least, it's highly likely to be incorrect if it wasn't).
• `length` needs to be the length that less than or equal to `capacity`.
• `capacity` needs to be the capacity that the pointer was allocated with.

Violating these may cause problems like corrupting the allocator's internal datastructures.

Examples

use std::ptr; use std::mem; fn main() { let mut v = vec![1, 2, 3]; // Pull out the various important pieces of information about `v` let p = v.as_mut_ptr(); let len = v.len(); let cap = v.capacity(); unsafe { // Cast `v` into the void: no destructor run, so we are in // complete control of the allocation to which `p` points. mem::forget(v); // Overwrite memory with 4, 5, 6 for i in 0..len as isize { ptr::write(p.offset(i), 4 + i); } // Put everything back together into a Vec let rebuilt = Vec::from_raw_parts(p, len, cap); assert_eq!(rebuilt, [4, 5, 6]); } }
```use std::ptr;
use std::mem;

fn main() {
let mut v = vec![1, 2, 3];

// Pull out the various important pieces of information about `v`
let p = v.as_mut_ptr();
let len = v.len();
let cap = v.capacity();

unsafe {
// Cast `v` into the void: no destructor run, so we are in
// complete control of the allocation to which `p` points.
mem::forget(v);

// Overwrite memory with 4, 5, 6
for i in 0..len as isize {
ptr::write(p.offset(i), 4 + i);
}

// Put everything back together into a Vec
let rebuilt = Vec::from_raw_parts(p, len, cap);
assert_eq!(rebuilt, [4, 5, 6]);
}
}```

`fn capacity(&self) -> usize`

Returns the number of elements the vector can hold without reallocating.

Examples

fn main() { let vec: Vec<i32> = Vec::with_capacity(10); assert_eq!(vec.capacity(), 10); }
```let vec: Vec<i32> = Vec::with_capacity(10);
assert_eq!(vec.capacity(), 10);```

`fn reserve(&mut self, additional: usize)`

Reserves capacity for at least `additional` more elements to be inserted in the given `Vec<T>`. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new capacity overflows `usize`.

Examples

fn main() { let mut vec = vec![1]; vec.reserve(10); assert!(vec.capacity() >= 11); }
```let mut vec = vec![1];
vec.reserve(10);
assert!(vec.capacity() >= 11);```

`fn reserve_exact(&mut self, additional: usize)`

Reserves the minimum capacity for exactly `additional` more elements to be inserted in the given `Vec<T>`. Does nothing if the capacity is already sufficient.

Note that the allocator may give the collection more space than it requests. Therefore capacity can not be relied upon to be precisely minimal. Prefer `reserve` if future insertions are expected.

Panics

Panics if the new capacity overflows `usize`.

Examples

fn main() { let mut vec = vec![1]; vec.reserve_exact(10); assert!(vec.capacity() >= 11); }
```let mut vec = vec![1];
vec.reserve_exact(10);
assert!(vec.capacity() >= 11);```

`fn shrink_to_fit(&mut self)`

Shrinks the capacity of the vector as much as possible.

It will drop down as close as possible to the length but the allocator may still inform the vector that there is space for a few more elements.

Examples

fn main() { let mut vec = Vec::with_capacity(10); vec.extend([1, 2, 3].iter().cloned()); assert_eq!(vec.capacity(), 10); vec.shrink_to_fit(); assert!(vec.capacity() >= 3); }
```let mut vec = Vec::with_capacity(10);
vec.extend([1, 2, 3].iter().cloned());
assert_eq!(vec.capacity(), 10);
vec.shrink_to_fit();
assert!(vec.capacity() >= 3);```

`fn into_boxed_slice(self) -> Box<[T]>`

Converts the vector into Box<[T]>.

Note that this will drop any excess capacity. Calling this and converting back to a vector with `into_vec()` is equivalent to calling `shrink_to_fit()`.

`fn truncate(&mut self, len: usize)`

Shorten a vector to be `len` elements long, dropping excess elements.

If `len` is greater than the vector's current length, this has no effect.

Examples

fn main() { let mut vec = vec![1, 2, 3, 4, 5]; vec.truncate(2); assert_eq!(vec, [1, 2]); }
```let mut vec = vec![1, 2, 3, 4, 5];
vec.truncate(2);
assert_eq!(vec, [1, 2]);```

1.7.0`fn as_slice(&self) -> &[T]`

Extracts a slice containing the entire vector.

Equivalent to `&s[..]`.

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

Extracts a mutable slice of the entire vector.

Equivalent to `&mut s[..]`.

`unsafe fn set_len(&mut self, len: usize)`

Sets the length of a vector.

This will explicitly set the size of the vector, without actually modifying its buffers, so it is up to the caller to ensure that the vector is actually the specified size.

Examples

fn main() { let mut v = vec![1, 2, 3, 4]; unsafe { v.set_len(1); } }
```let mut v = vec![1, 2, 3, 4];
unsafe {
v.set_len(1);
}```

`fn swap_remove(&mut self, index: usize) -> T`

Removes an element from anywhere in the vector and return it, replacing it with the last element.

This does not preserve ordering, but is O(1).

Panics

Panics if `index` is out of bounds.

Examples

fn main() { let mut v = vec!["foo", "bar", "baz", "qux"]; assert_eq!(v.swap_remove(1), "bar"); assert_eq!(v, ["foo", "qux", "baz"]); assert_eq!(v.swap_remove(0), "foo"); assert_eq!(v, ["baz", "qux"]); }
```let mut v = vec!["foo", "bar", "baz", "qux"];

assert_eq!(v.swap_remove(1), "bar");
assert_eq!(v, ["foo", "qux", "baz"]);

assert_eq!(v.swap_remove(0), "foo");
assert_eq!(v, ["baz", "qux"]);```

`fn insert(&mut self, index: usize, element: T)`

Inserts an element at position `index` within the vector, shifting all elements after it to the right.

Panics

Panics if `index` is greater than the vector's length.

Examples

fn main() { let mut vec = vec![1, 2, 3]; vec.insert(1, 4); assert_eq!(vec, [1, 4, 2, 3]); vec.insert(4, 5); assert_eq!(vec, [1, 4, 2, 3, 5]); }
```let mut vec = vec![1, 2, 3];
vec.insert(1, 4);
assert_eq!(vec, [1, 4, 2, 3]);
vec.insert(4, 5);
assert_eq!(vec, [1, 4, 2, 3, 5]);```

`fn remove(&mut self, index: usize) -> T`

Removes and returns the element at position `index` within the vector, shifting all elements after it to the left.

Panics

Panics if `index` is out of bounds.

Examples

fn main() { let mut v = vec![1, 2, 3]; assert_eq!(v.remove(1), 2); assert_eq!(v, [1, 3]); }
```let mut v = vec![1, 2, 3];
assert_eq!(v.remove(1), 2);
assert_eq!(v, [1, 3]);```

`fn retain<F>(&mut self, f: F) where F: FnMut(&T) -> bool`

Retains only the elements specified by the predicate.

In other words, remove all elements `e` such that `f(&e)` returns false. This method operates in place and preserves the order of the retained elements.

Examples

fn main() { let mut vec = vec![1, 2, 3, 4]; vec.retain(|&x| x%2 == 0); assert_eq!(vec, [2, 4]); }
```let mut vec = vec![1, 2, 3, 4];
vec.retain(|&x| x%2 == 0);
assert_eq!(vec, [2, 4]);```

`fn push(&mut self, value: T)`

Appends an element to the back of a collection.

Panics

Panics if the number of elements in the vector overflows a `usize`.

Examples

fn main() { let mut vec = vec![1, 2]; vec.push(3); assert_eq!(vec, [1, 2, 3]); }
```let mut vec = vec![1, 2];
vec.push(3);
assert_eq!(vec, [1, 2, 3]);```

`fn pop(&mut self) -> Option<T>`

Removes the last element from a vector and returns it, or `None` if it is empty.

Examples

fn main() { let mut vec = vec![1, 2, 3]; assert_eq!(vec.pop(), Some(3)); assert_eq!(vec, [1, 2]); }
```let mut vec = vec![1, 2, 3];
assert_eq!(vec.pop(), Some(3));
assert_eq!(vec, [1, 2]);```

1.4.0`fn append(&mut self, other: &mut Vec<T>)`

Moves all the elements of `other` into `Self`, leaving `other` empty.

Panics

Panics if the number of elements in the vector overflows a `usize`.

Examples

fn main() { let mut vec = vec![1, 2, 3]; let mut vec2 = vec![4, 5, 6]; vec.append(&mut vec2); assert_eq!(vec, [1, 2, 3, 4, 5, 6]); assert_eq!(vec2, []); }
```let mut vec = vec![1, 2, 3];
let mut vec2 = vec![4, 5, 6];
vec.append(&mut vec2);
assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
assert_eq!(vec2, []);```

1.6.0`fn drain<R>(&mut self, range: R) -> Drain<T> where R: RangeArgument<usize>`

Create a draining iterator that removes the specified range in the vector and yields the removed items.

Note 1: The element range is removed even if the iterator is not consumed until the end.

Note 2: It is unspecified how many elements are removed from the vector, if the `Drain` value is leaked.

Panics

Panics if the starting point is greater than the end point or if the end point is greater than the length of the vector.

Examples

fn main() { let mut v = vec![1, 2, 3]; let u: Vec<_> = v.drain(1..).collect(); assert_eq!(v, &[1]); assert_eq!(u, &[2, 3]); // A full range clears the vector v.drain(..); assert_eq!(v, &[]); }
```let mut v = vec![1, 2, 3];
let u: Vec<_> = v.drain(1..).collect();
assert_eq!(v, &[1]);
assert_eq!(u, &[2, 3]);

// A full range clears the vector
v.drain(..);
assert_eq!(v, &[]);```

`fn clear(&mut self)`

Clears the vector, removing all values.

Examples

fn main() { let mut v = vec![1, 2, 3]; v.clear(); assert!(v.is_empty()); }
```let mut v = vec![1, 2, 3];

v.clear();

assert!(v.is_empty());```

`fn len(&self) -> usize`

Returns the number of elements in the vector.

Examples

fn main() { let a = vec![1, 2, 3]; assert_eq!(a.len(), 3); }
```let a = vec![1, 2, 3];
assert_eq!(a.len(), 3);```

`fn is_empty(&self) -> bool`

Returns `true` if the vector contains no elements.

Examples

fn main() { let mut v = Vec::new(); assert!(v.is_empty()); v.push(1); assert!(!v.is_empty()); }
```let mut v = Vec::new();
assert!(v.is_empty());

v.push(1);
assert!(!v.is_empty());```

1.4.0`fn split_off(&mut self, at: usize) -> Vec<T>`

Splits the collection into two at the given index.

Returns a newly allocated `Self`. `self` contains elements `[0, at)`, and the returned `Self` contains elements `[at, len)`.

Note that the capacity of `self` does not change.

Panics

Panics if `at > len`.

Examples

fn main() { let mut vec = vec![1,2,3]; let vec2 = vec.split_off(1); assert_eq!(vec, [1]); assert_eq!(vec2, [2, 3]); }
```let mut vec = vec![1,2,3];
let vec2 = vec.split_off(1);
assert_eq!(vec, [1]);
assert_eq!(vec2, [2, 3]);```

Methods from Deref<Target=[T]>

`fn len(&self) -> usize`

Returns the number of elements in the slice.

Example

fn main() { let a = [1, 2, 3]; assert_eq!(a.len(), 3); }
```let a = [1, 2, 3];
assert_eq!(a.len(), 3);```

`fn is_empty(&self) -> bool`

Returns true if the slice has a length of 0

Example

fn main() { let a = [1, 2, 3]; assert!(!a.is_empty()); }
```let a = [1, 2, 3];
assert!(!a.is_empty());```

`fn first(&self) -> Option<&T>`

Returns the first element of a slice, or `None` if it is empty.

Examples

fn main() { let v = [10, 40, 30]; assert_eq!(Some(&10), v.first()); let w: &[i32] = &[]; assert_eq!(None, w.first()); }
```let v = [10, 40, 30];
assert_eq!(Some(&10), v.first());

let w: &[i32] = &[];
assert_eq!(None, w.first());```

`fn first_mut(&mut self) -> Option<&mut T>`

Returns a mutable pointer to the first element of a slice, or `None` if it is empty

1.5.0`fn split_first(&self) -> Option<(&T, &[T])>`

Returns the first and all the rest of the elements of a slice.

1.5.0`fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])>`

Returns the first and all the rest of the elements of a slice.

1.5.0`fn split_last(&self) -> Option<(&T, &[T])>`

Returns the last and all the rest of the elements of a slice.

1.5.0`fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])>`

Returns the last and all the rest of the elements of a slice.

`fn last(&self) -> Option<&T>`

Returns the last element of a slice, or `None` if it is empty.

Examples

fn main() { let v = [10, 40, 30]; assert_eq!(Some(&30), v.last()); let w: &[i32] = &[]; assert_eq!(None, w.last()); }
```let v = [10, 40, 30];
assert_eq!(Some(&30), v.last());

let w: &[i32] = &[];
assert_eq!(None, w.last());```

`fn last_mut(&mut self) -> Option<&mut T>`

Returns a mutable pointer to the last item in the slice.

`fn get(&self, index: usize) -> Option<&T>`

Returns the element of a slice at the given index, or `None` if the index is out of bounds.

Examples

fn main() { let v = [10, 40, 30]; assert_eq!(Some(&40), v.get(1)); assert_eq!(None, v.get(3)); }
```let v = [10, 40, 30];
assert_eq!(Some(&40), v.get(1));
assert_eq!(None, v.get(3));```

`fn get_mut(&mut self, index: usize) -> Option<&mut T>`

Returns a mutable reference to the element at the given index, or `None` if the index is out of bounds

`unsafe fn get_unchecked(&self, index: usize) -> &T`

Returns a pointer to the element at the given index, without doing bounds checking.

`unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T`

Returns an unsafe mutable pointer to the element in index

`fn as_ptr(&self) -> *const T`

Returns an raw pointer to the slice's buffer

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

Modifying the slice may cause its buffer to be reallocated, which would also make any pointers to it invalid.

`fn as_mut_ptr(&mut self) -> *mut T`

Returns an unsafe mutable pointer to the slice's buffer.

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

Modifying the slice may cause its buffer to be reallocated, which would also make any pointers to it invalid.

`fn swap(&mut self, a: usize, b: usize)`

Swaps two elements in a slice.

Arguments

• a - The index of the first element
• b - The index of the second element

Panics

Panics if `a` or `b` are out of bounds.

Example

fn main() { let mut v = ["a", "b", "c", "d"]; v.swap(1, 3); assert!(v == ["a", "d", "c", "b"]); }
```let mut v = ["a", "b", "c", "d"];
v.swap(1, 3);
assert!(v == ["a", "d", "c", "b"]);```

`fn reverse(&mut self)`

Reverse the order of elements in a slice, in place.

Example

fn main() { let mut v = [1, 2, 3]; v.reverse(); assert!(v == [3, 2, 1]); }
```let mut v = [1, 2, 3];
v.reverse();
assert!(v == [3, 2, 1]);```

`fn iter(&self) -> Iter<T>`

Returns an iterator over the slice.

`fn iter_mut(&mut self) -> IterMut<T>`

Returns an iterator that allows modifying each value

`fn windows(&self, size: usize) -> Windows<T>`

Returns an iterator over all contiguous windows of length `size`. The windows overlap. If the slice is shorter than `size`, the iterator returns no values.

Panics

Panics if `size` is 0.

Example

Print the adjacent pairs of a slice (i.e. `[1,2]`, `[2,3]`, `[3,4]`):

fn main() { let v = &[1, 2, 3, 4]; for win in v.windows(2) { println!("{:?}", win); } }
```let v = &[1, 2, 3, 4];
for win in v.windows(2) {
println!("{:?}", win);
}```

`fn chunks(&self, size: usize) -> Chunks<T>`

Returns an iterator over `size` elements of the slice at a time. The chunks are slices and do not overlap. If `size` does not divide the length of the slice, then the last chunk will not have length `size`.

Panics

Panics if `size` is 0.

Example

Print the slice two elements at a time (i.e. `[1,2]`, `[3,4]`, `[5]`):

fn main() { let v = &[1, 2, 3, 4, 5]; for win in v.chunks(2) { println!("{:?}", win); } }
```let v = &[1, 2, 3, 4, 5];
for win in v.chunks(2) {
println!("{:?}", win);
}```

`fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T>`

Returns an iterator over `chunk_size` elements of the slice at a time. The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the length of the slice, then the last chunk will not have length `chunk_size`.

Panics

Panics if `chunk_size` is 0.

`fn split_at(&self, mid: usize) -> (&[T], &[T])`

Divides one slice into two at an index.

The first will contain all indices from `[0, mid)` (excluding the index `mid` itself) and the second will contain all indices from `[mid, len)` (excluding the index `len` itself).

Panics

Panics if `mid > len`.

Examples

fn main() { let v = [10, 40, 30, 20, 50]; let (v1, v2) = v.split_at(2); assert_eq!([10, 40], v1); assert_eq!([30, 20, 50], v2); }
```let v = [10, 40, 30, 20, 50];
let (v1, v2) = v.split_at(2);
assert_eq!([10, 40], v1);
assert_eq!([30, 20, 50], v2);```

`fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T])`

Divides one `&mut` into two at an index.

The first will contain all indices from `[0, mid)` (excluding the index `mid` itself) and the second will contain all indices from `[mid, len)` (excluding the index `len` itself).

Panics

Panics if `mid > len`.

Example

fn main() { let mut v = [1, 2, 3, 4, 5, 6]; // scoped to restrict the lifetime of the borrows { let (left, right) = v.split_at_mut(0); assert!(left == []); assert!(right == [1, 2, 3, 4, 5, 6]); } { let (left, right) = v.split_at_mut(2); assert!(left == [1, 2]); assert!(right == [3, 4, 5, 6]); } { let (left, right) = v.split_at_mut(6); assert!(left == [1, 2, 3, 4, 5, 6]); assert!(right == []); } }
```let mut v = [1, 2, 3, 4, 5, 6];

// scoped to restrict the lifetime of the borrows
{
let (left, right) = v.split_at_mut(0);
assert!(left == []);
assert!(right == [1, 2, 3, 4, 5, 6]);
}

{
let (left, right) = v.split_at_mut(2);
assert!(left == [1, 2]);
assert!(right == [3, 4, 5, 6]);
}

{
let (left, right) = v.split_at_mut(6);
assert!(left == [1, 2, 3, 4, 5, 6]);
assert!(right == []);
}```

`fn split<F>(&self, pred: F) -> Split<T, F> where F: FnMut(&T) -> bool`

Returns an iterator over subslices separated by elements that match `pred`. The matched element is not contained in the subslices.

Examples

Print the slice split by numbers divisible by 3 (i.e. `[10, 40]`, `[20]`, `[50]`):

fn main() { let v = [10, 40, 30, 20, 60, 50]; for group in v.split(|num| *num % 3 == 0) { println!("{:?}", group); } }
```let v = [10, 40, 30, 20, 60, 50];
for group in v.split(|num| *num % 3 == 0) {
println!("{:?}", group);
}```

`fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F> where F: FnMut(&T) -> bool`

Returns an iterator over mutable subslices separated by elements that match `pred`. The matched element is not contained in the subslices.

`fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F> where F: FnMut(&T) -> bool`

Returns an iterator over subslices separated by elements that match `pred`, limited to returning at most `n` items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`, `[20, 60, 50]`):

fn main() { let v = [10, 40, 30, 20, 60, 50]; for group in v.splitn(2, |num| *num % 3 == 0) { println!("{:?}", group); } }
```let v = [10, 40, 30, 20, 60, 50];
for group in v.splitn(2, |num| *num % 3 == 0) {
println!("{:?}", group);
}```

`fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F> where F: FnMut(&T) -> bool`

Returns an iterator over subslices separated by elements that match `pred`, limited to returning at most `n` items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

`fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F> where F: FnMut(&T) -> bool`

Returns an iterator over subslices separated by elements that match `pred` limited to returning at most `n` items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once, starting from the end, by numbers divisible by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):

fn main() { let v = [10, 40, 30, 20, 60, 50]; for group in v.rsplitn(2, |num| *num % 3 == 0) { println!("{:?}", group); } }
```let v = [10, 40, 30, 20, 60, 50];
for group in v.rsplitn(2, |num| *num % 3 == 0) {
println!("{:?}", group);
}```

`fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F> where F: FnMut(&T) -> bool`

Returns an iterator over subslices separated by elements that match `pred` limited to returning at most `n` items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

`fn contains(&self, x: &T) -> bool where T: PartialEq<T>`

Returns true if the slice contains an element with the given value.

Examples

fn main() { let v = [10, 40, 30]; assert!(v.contains(&30)); assert!(!v.contains(&50)); }
```let v = [10, 40, 30];
assert!(v.contains(&30));
assert!(!v.contains(&50));```

`fn starts_with(&self, needle: &[T]) -> bool where T: PartialEq<T>`

Returns true if `needle` is a prefix of the slice.

Examples

fn main() { let v = [10, 40, 30]; assert!(v.starts_with(&[10])); assert!(v.starts_with(&[10, 40])); assert!(!v.starts_with(&[50])); assert!(!v.starts_with(&[10, 50])); }
```let v = [10, 40, 30];
assert!(v.starts_with(&[10]));
assert!(v.starts_with(&[10, 40]));
assert!(!v.starts_with(&[50]));
assert!(!v.starts_with(&[10, 50]));```

`fn ends_with(&self, needle: &[T]) -> bool where T: PartialEq<T>`

Returns true if `needle` is a suffix of the slice.

Examples

fn main() { let v = [10, 40, 30]; assert!(v.ends_with(&[30])); assert!(v.ends_with(&[40, 30])); assert!(!v.ends_with(&[50])); assert!(!v.ends_with(&[50, 30])); }
```let v = [10, 40, 30];
assert!(v.ends_with(&[30]));
assert!(v.ends_with(&[40, 30]));
assert!(!v.ends_with(&[50]));
assert!(!v.ends_with(&[50, 30]));```

Binary search a sorted slice for a given element.

If the value is found then `Ok` is returned, containing the index of the matching element; if the value is not found then `Err` is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Example

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in `[1,4]`.

fn main() { let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; assert_eq!(s.binary_search(&13), Ok(9)); assert_eq!(s.binary_search(&4), Err(7)); assert_eq!(s.binary_search(&100), Err(13)); let r = s.binary_search(&1); assert!(match r { Ok(1...4) => true, _ => false, }); }
```let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

assert_eq!(s.binary_search(&13),  Ok(9));
assert_eq!(s.binary_search(&4),   Err(7));
assert_eq!(s.binary_search(&100), Err(13));
let r = s.binary_search(&1);
assert!(match r { Ok(1...4) => true, _ => false, });```

`fn binary_search_by<F>(&self, f: F) -> Result<usize, usize> where F: FnMut(&T) -> Ordering`

Binary search a sorted slice with a comparator function.

The comparator function should implement an order consistent with the sort order of the underlying slice, returning an order code that indicates whether its argument is `Less`, `Equal` or `Greater` the desired target.

If a matching value is found then returns `Ok`, containing the index for the matched element; if no match is found then `Err` is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Example

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in `[1,4]`.

fn main() { let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; let seek = 13; assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9)); let seek = 4; assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7)); let seek = 100; assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13)); let seek = 1; let r = s.binary_search_by(|probe| probe.cmp(&seek)); assert!(match r { Ok(1...4) => true, _ => false, }); }
```let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];

let seek = 13;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
let seek = 4;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
let seek = 100;
assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
let seek = 1;
let r = s.binary_search_by(|probe| probe.cmp(&seek));
assert!(match r { Ok(1...4) => true, _ => false, });```

`fn sort(&mut self) where T: Ord`

Sorts the slice, in place.

This is equivalent to `self.sort_by(|a, b| a.cmp(b))`.

This is a stable sort.

Examples

fn main() { let mut v = [-5, 4, 1, -3, 2]; v.sort(); assert!(v == [-5, -3, 1, 2, 4]); }
```let mut v = [-5, 4, 1, -3, 2];

v.sort();
assert!(v == [-5, -3, 1, 2, 4]);```

1.7.0`fn sort_by_key<B, F>(&mut self, f: F) where B: Ord, F: FnMut(&T) -> B`

Sorts the slice, in place, using `key` to extract a key by which to order the sort by.

This sort is `O(n log n)` worst-case and stable, but allocates approximately `2 * n`, where `n` is the length of `self`.

This is a stable sort.

Examples

fn main() { let mut v = [-5i32, 4, 1, -3, 2]; v.sort_by_key(|k| k.abs()); assert!(v == [1, 2, -3, 4, -5]); }
```let mut v = [-5i32, 4, 1, -3, 2];

v.sort_by_key(|k| k.abs());
assert!(v == [1, 2, -3, 4, -5]);```

`fn sort_by<F>(&mut self, compare: F) where F: FnMut(&T, &T) -> Ordering`

Sorts the slice, in place, using `compare` to compare elements.

This sort is `O(n log n)` worst-case and stable, but allocates approximately `2 * n`, where `n` is the length of `self`.

Examples

fn main() { let mut v = [5, 4, 1, 3, 2]; v.sort_by(|a, b| a.cmp(b)); assert!(v == [1, 2, 3, 4, 5]); // reverse sorting v.sort_by(|a, b| b.cmp(a)); assert!(v == [5, 4, 3, 2, 1]); }
```let mut v = [5, 4, 1, 3, 2];
v.sort_by(|a, b| a.cmp(b));
assert!(v == [1, 2, 3, 4, 5]);

// reverse sorting
v.sort_by(|a, b| b.cmp(a));
assert!(v == [5, 4, 3, 2, 1]);```

1.7.0`fn clone_from_slice(&mut self, src: &[T]) where T: Clone`

Copies the elements from `src` into `self`.

The length of this slice must be the same as the slice passed in.

Panics

This function will panic if the two slices have different lengths.

Example

fn main() { let mut dst = [0, 0, 0]; let src = [1, 2, 3]; dst.clone_from_slice(&src); assert!(dst == [1, 2, 3]); }
```let mut dst = [0, 0, 0];
let src = [1, 2, 3];

dst.clone_from_slice(&src);
assert!(dst == [1, 2, 3]);```

1.9.0`fn copy_from_slice(&mut self, src: &[T]) where T: Copy`

Copies all elements from `src` into `self`, using a memcpy.

The length of `src` must be the same as `self`.

Panics

This function will panic if the two slices have different lengths.

Example

fn main() { let mut dst = [0, 0, 0]; let src = [1, 2, 3]; dst.copy_from_slice(&src); assert_eq!(src, dst); }
```let mut dst = [0, 0, 0];
let src = [1, 2, 3];

dst.copy_from_slice(&src);
assert_eq!(src, dst);```

`fn to_vec(&self) -> Vec<T> where T: Clone`

Copies `self` into a new `Vec`.

`fn into_vec(self: Box<[T]>) -> Vec<T>`

Converts `self` into a vector without clones or allocation.