Struct sized_chunks::sized_chunk::Chunk

source · [−]
pub struct Chunk<A, const N: usize> { /* private fields */ }
Expand description

A fixed capacity smart array.

An inline array of items with a variable length but a fixed, preallocated capacity given by the N type.

It’s ‘smart’ because it’s able to reorganise its contents based on expected behaviour. If you construct one using push_back, it will be laid out like a Vec with space at the end. If you push_front it will start filling in values from the back instead of the front, so that you still get linear time push as long as you don’t reverse direction. If you do, and there’s no room at the end you’re pushing to, it’ll shift its contents over to the other side, creating more space to push into. This technique is tuned for Chunk’s expected use case in im::Vector: usually, chunks always see either push_front or push_back, but not both unless they move around inside the tree, in which case they’re able to reorganise themselves with reasonable efficiency to suit their new usage patterns.

It maintains a left index and a right index instead of a simple length counter in order to accomplish this, much like a ring buffer would, except that the Chunk keeps all its items sequentially in memory so that you can always get a &[A] slice for them, at the price of the occasional reordering operation. The allocated size of a Chunk is thus usize * 2 + A * N.

This technique also lets us choose to shift the shortest side to account for the inserted or removed element when performing insert and remove operations, unlike Vec where you always need to shift the right hand side.

Unlike a Vec, the Chunk has a fixed capacity and cannot grow beyond it. Being intended for low level use, it expects you to know or test whether you’re pushing to a full array, and has an API more geared towards panics than returning Options, on the assumption that you know what you’re doing. Of course, if you don’t, you can expect it to panic immediately rather than do something undefined and usually bad.

Isn’t this just a less efficient ring buffer?

You might be wondering why you would want to use this data structure rather than a RingBuffer, which is similar but doesn’t need to shift its content around when it hits the sides of the allocated buffer. The answer is that Chunk can be dereferenced into a slice, while a ring buffer can not. You’ll also save a few cycles on index lookups, as a Chunk’s data is guaranteed to be contiguous in memory, so there’s no need to remap logical indices to a ring buffer’s physical layout.

Examples

// Construct a chunk with a 64 item capacity
let mut chunk = Chunk::<i32, 64>::new();
// Fill it with descending numbers
chunk.extend((0..64).rev());
// It derefs to a slice so we can use standard slice methods
chunk.sort();
// It's got all the amenities like `FromIterator` and `Eq`
let expected: Chunk<i32, 64> = (0..64).collect();
assert_eq!(expected, chunk);

Implementations

The maximum number of elements this Chunk can contain.

Construct a new empty chunk.

Construct a new chunk with one item.

Construct a new chunk with two items.

Construct a new chunk and move every item from other into the new chunk.

Time: O(n)

Construct a new chunk and populate it by taking count items from the iterator iter.

Panics if the iterator contains less than count items.

Time: O(n)

Construct a new chunk and populate it by taking count items from the front of other.

Time: O(n) for the number of items moved

Construct a new chunk and populate it by taking count items from the back of other.

Time: O(n) for the number of items moved

Get the length of the chunk.

Test if the chunk is empty.

Test if the chunk is at capacity.

Push an item to the front of the chunk.

Panics if the capacity of the chunk is exceeded.

Time: O(1) if there’s room at the front, O(n) otherwise

Push an item to the back of the chunk.

Panics if the capacity of the chunk is exceeded.

Time: O(1) if there’s room at the back, O(n) otherwise

Pop an item off the front of the chunk.

Panics if the chunk is empty.

Time: O(1)

Pop an item off the back of the chunk.

Panics if the chunk is empty.

Time: O(1)

Discard all items up to but not including index.

Panics if index is out of bounds.

Time: O(n) for the number of items dropped

Discard all items from index onward.

Panics if index is out of bounds.

Time: O(n) for the number of items dropped

Split a chunk into two, the original chunk containing everything up to index and the returned chunk containing everything from index onwards.

Panics if index is out of bounds.

Time: O(n) for the number of items in the new chunk

Remove all items from other and append them to the back of self.

Panics if the capacity of the chunk is exceeded.

Time: O(n) for the number of items moved

Remove count items from the front of other and append them to the back of self.

Panics if self doesn’t have count items left, or if other has fewer than count items.

Time: O(n) for the number of items moved

Remove count items from the back of other and append them to the front of self.

Panics if self doesn’t have count items left, or if other has fewer than count items.

Time: O(n) for the number of items moved

Update the value at index index, returning the old value.

Panics if index is out of bounds.

Time: O(1)

Insert a new value at index index, shifting all the following values to the right.

Panics if the index is out of bounds or the chunk is full.

Time: O(n) for the number of elements shifted

Insert a new value into the chunk in sorted order.

This assumes every element of the chunk is already in sorted order. If not, the value will still be inserted but the ordering is not guaranteed.

Time: O(log n) to find the insert position, then O(n) for the number of elements shifted.

Examples
let mut chunk = Chunk::<i32, 64>::from_iter(0..5);
chunk.insert_ordered(3);
assert_eq!(&[0, 1, 2, 3, 3, 4], chunk.as_slice());

Insert multiple values at index index, shifting all the following values to the right.

Panics if the index is out of bounds or the chunk doesn’t have room for all the values.

Time: O(m+n) where m is the number of elements inserted and n is the number of elements following the insertion index. Calling insert repeatedly would be O(m*n).

Remove the value at index index, shifting all the following values to the left.

Returns the removed value.

Panics if the index is out of bounds.

Time: O(n) for the number of items shifted

Construct an iterator that drains values from the front of the chunk.

Discard the contents of the chunk.

Time: O(n)

Get a reference to the contents of the chunk as a slice.

Get a reference to the contents of the chunk as a mutable slice.

Methods from Deref<Target = [A]>

🔬 This is a nightly-only experimental API. (slice_flatten)

Takes a &[[T; N]], and flattens it to a &[T].

Panics

This panics if the length of the resulting slice would overflow a usize.

This is only possible when flattening a slice of arrays of zero-sized types, and thus tends to be irrelevant in practice. If size_of::<T>() > 0, this will never panic.

Examples
#![feature(slice_flatten)]

assert_eq!([[1, 2, 3], [4, 5, 6]].flatten(), &[1, 2, 3, 4, 5, 6]);

assert_eq!(
    [[1, 2, 3], [4, 5, 6]].flatten(),
    [[1, 2], [3, 4], [5, 6]].flatten(),
);

let slice_of_empty_arrays: &[[i32; 0]] = &[[], [], [], [], []];
assert!(slice_of_empty_arrays.flatten().is_empty());

let empty_slice_of_arrays: &[[u32; 10]] = &[];
assert!(empty_slice_of_arrays.flatten().is_empty());
🔬 This is a nightly-only experimental API. (slice_flatten)

Takes a &mut [[T; N]], and flattens it to a &mut [T].

Panics

This panics if the length of the resulting slice would overflow a usize.

This is only possible when flattening a slice of arrays of zero-sized types, and thus tends to be irrelevant in practice. If size_of::<T>() > 0, this will never panic.

Examples
#![feature(slice_flatten)]

fn add_5_to_all(slice: &mut [i32]) {
    for i in slice {
        *i += 5;
    }
}

let mut array = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
add_5_to_all(array.flatten_mut());
assert_eq!(array, [[6, 7, 8], [9, 10, 11], [12, 13, 14]]);

Returns the number of elements in the slice.

Examples
let a = [1, 2, 3];
assert_eq!(a.len(), 3);

Returns true if the slice has a length of 0.

Examples
let a = [1, 2, 3];
assert!(!a.is_empty());

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

Examples
let v = [10, 40, 30];
assert_eq!(Some(&10), v.first());

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

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

Examples
let x = &mut [0, 1, 2];

if let Some(first) = x.first_mut() {
    *first = 5;
}
assert_eq!(x, &[5, 1, 2]);

Returns the first and all the rest of the elements of the slice, or None if it is empty.

Examples
let x = &[0, 1, 2];

if let Some((first, elements)) = x.split_first() {
    assert_eq!(first, &0);
    assert_eq!(elements, &[1, 2]);
}

Returns the first and all the rest of the elements of the slice, or None if it is empty.

Examples
let x = &mut [0, 1, 2];

if let Some((first, elements)) = x.split_first_mut() {
    *first = 3;
    elements[0] = 4;
    elements[1] = 5;
}
assert_eq!(x, &[3, 4, 5]);

Returns the last and all the rest of the elements of the slice, or None if it is empty.

Examples
let x = &[0, 1, 2];

if let Some((last, elements)) = x.split_last() {
    assert_eq!(last, &2);
    assert_eq!(elements, &[0, 1]);
}

Returns the last and all the rest of the elements of the slice, or None if it is empty.

Examples
let x = &mut [0, 1, 2];

if let Some((last, elements)) = x.split_last_mut() {
    *last = 3;
    elements[0] = 4;
    elements[1] = 5;
}
assert_eq!(x, &[4, 5, 3]);

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

Examples
let v = [10, 40, 30];
assert_eq!(Some(&30), v.last());

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

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

Examples
let x = &mut [0, 1, 2];

if let Some(last) = x.last_mut() {
    *last = 10;
}
assert_eq!(x, &[0, 1, 10]);

Returns a reference to an element or subslice depending on the type of index.

  • If given a position, returns a reference to the element at that position or None if out of bounds.
  • If given a range, returns the subslice corresponding to that range, or None if out of bounds.
Examples
let v = [10, 40, 30];
assert_eq!(Some(&40), v.get(1));
assert_eq!(Some(&[10, 40][..]), v.get(0..2));
assert_eq!(None, v.get(3));
assert_eq!(None, v.get(0..4));

Returns a mutable reference to an element or subslice depending on the type of index (see get) or None if the index is out of bounds.

Examples
let x = &mut [0, 1, 2];

if let Some(elem) = x.get_mut(1) {
    *elem = 42;
}
assert_eq!(x, &[0, 42, 2]);

Returns a reference to an element or subslice, without doing bounds checking.

For a safe alternative see get.

Safety

Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used.

Examples
let x = &[1, 2, 4];

unsafe {
    assert_eq!(x.get_unchecked(1), &2);
}

Returns a mutable reference to an element or subslice, without doing bounds checking.

For a safe alternative see get_mut.

Safety

Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used.

Examples
let x = &mut [1, 2, 4];

unsafe {
    let elem = x.get_unchecked_mut(1);
    *elem = 13;
}
assert_eq!(x, &[1, 13, 4]);

Returns a 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.

The caller must also ensure that the memory the pointer (non-transitively) points to is never written to (except inside an UnsafeCell) using this pointer or any pointer derived from it. If you need to mutate the contents of the slice, use as_mut_ptr.

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

Examples
let x = &[1, 2, 4];
let x_ptr = x.as_ptr();

unsafe {
    for i in 0..x.len() {
        assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
    }
}

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 container referenced by this slice may cause its buffer to be reallocated, which would also make any pointers to it invalid.

Examples
let x = &mut [1, 2, 4];
let x_ptr = x.as_mut_ptr();

unsafe {
    for i in 0..x.len() {
        *x_ptr.add(i) += 2;
    }
}
assert_eq!(x, &[3, 4, 6]);

Returns the two raw pointers spanning the slice.

The returned range is half-open, which means that the end pointer points one past the last element of the slice. This way, an empty slice is represented by two equal pointers, and the difference between the two pointers represents the size of the slice.

See as_ptr for warnings on using these pointers. The end pointer requires extra caution, as it does not point to a valid element in the slice.

This function is useful for interacting with foreign interfaces which use two pointers to refer to a range of elements in memory, as is common in C++.

It can also be useful to check if a pointer to an element refers to an element of this slice:

let a = [1, 2, 3];
let x = &a[1] as *const _;
let y = &5 as *const _;

assert!(a.as_ptr_range().contains(&x));
assert!(!a.as_ptr_range().contains(&y));

Returns the two unsafe mutable pointers spanning the slice.

The returned range is half-open, which means that the end pointer points one past the last element of the slice. This way, an empty slice is represented by two equal pointers, and the difference between the two pointers represents the size of the slice.

See as_mut_ptr for warnings on using these pointers. The end pointer requires extra caution, as it does not point to a valid element in the slice.

This function is useful for interacting with foreign interfaces which use two pointers to refer to a range of elements in memory, as is common in C++.

Swaps two elements in the 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.

Examples
let mut v = ["a", "b", "c", "d", "e"];
v.swap(2, 4);
assert!(v == ["a", "b", "e", "d", "c"]);
🔬 This is a nightly-only experimental API. (slice_swap_unchecked)

Swaps two elements in the slice, without doing bounds checking.

For a safe alternative see swap.

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

Calling this method with an out-of-bounds index is undefined behavior. The caller has to ensure that a < self.len() and b < self.len().

Examples
#![feature(slice_swap_unchecked)]

let mut v = ["a", "b", "c", "d"];
// SAFETY: we know that 1 and 3 are both indices of the slice
unsafe { v.swap_unchecked(1, 3) };
assert!(v == ["a", "d", "c", "b"]);

Reverses the order of elements in the slice, in place.

Examples
let mut v = [1, 2, 3];
v.reverse();
assert!(v == [3, 2, 1]);

Returns an iterator over the slice.

Examples
let x = &[1, 2, 4];
let mut iterator = x.iter();

assert_eq!(iterator.next(), Some(&1));
assert_eq!(iterator.next(), Some(&2));
assert_eq!(iterator.next(), Some(&4));
assert_eq!(iterator.next(), None);

Returns an iterator that allows modifying each value.

Examples
let x = &mut [1, 2, 4];
for elem in x.iter_mut() {
    *elem += 2;
}
assert_eq!(x, &[3, 4, 6]);

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.

Examples
let slice = ['r', 'u', 's', 't'];
let mut iter = slice.windows(2);
assert_eq!(iter.next().unwrap(), &['r', 'u']);
assert_eq!(iter.next().unwrap(), &['u', 's']);
assert_eq!(iter.next().unwrap(), &['s', 't']);
assert!(iter.next().is_none());

If the slice is shorter than size:

let slice = ['f', 'o', 'o'];
let mut iter = slice.windows(4);
assert!(iter.next().is_none());

Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.

The chunks are 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.

See chunks_exact for a variant of this iterator that returns chunks of always exactly chunk_size elements, and rchunks for the same iterator but starting at the end of the slice.

Panics

Panics if chunk_size is 0.

Examples
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.chunks(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert_eq!(iter.next().unwrap(), &['m']);
assert!(iter.next().is_none());

Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.

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.

See chunks_exact_mut for a variant of this iterator that returns chunks of always exactly chunk_size elements, and rchunks_mut for the same iterator but starting at the end of the slice.

Panics

Panics if chunk_size is 0.

Examples
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

for chunk in v.chunks_mut(2) {
    for elem in chunk.iter_mut() {
        *elem += count;
    }
    count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 3]);

Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.

The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted and can be retrieved from the remainder function of the iterator.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks.

See chunks for a variant of this iterator that also returns the remainder as a smaller chunk, and rchunks_exact for the same iterator but starting at the end of the slice.

Panics

Panics if chunk_size is 0.

Examples
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.chunks_exact(2);
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['m']);

Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.

The chunks are mutable slices, and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted and can be retrieved from the into_remainder function of the iterator.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks_mut.

See chunks_mut for a variant of this iterator that also returns the remainder as a smaller chunk, and rchunks_exact_mut for the same iterator but starting at the end of the slice.

Panics

Panics if chunk_size is 0.

Examples
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

for chunk in v.chunks_exact_mut(2) {
    for elem in chunk.iter_mut() {
        *elem += count;
    }
    count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 0]);
🔬 This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.

Safety

This may only be called when

  • The slice splits exactly into N-element chunks (aka self.len() % N == 0).
  • N != 0.
Examples
#![feature(slice_as_chunks)]
let slice: &[char] = &['l', 'o', 'r', 'e', 'm', '!'];
let chunks: &[[char; 1]] =
    // SAFETY: 1-element chunks never have remainder
    unsafe { slice.as_chunks_unchecked() };
assert_eq!(chunks, &[['l'], ['o'], ['r'], ['e'], ['m'], ['!']]);
let chunks: &[[char; 3]] =
    // SAFETY: The slice length (6) is a multiple of 3
    unsafe { slice.as_chunks_unchecked() };
assert_eq!(chunks, &[['l', 'o', 'r'], ['e', 'm', '!']]);

// These would be unsound:
// let chunks: &[[_; 5]] = slice.as_chunks_unchecked() // The slice length is not a multiple of 5
// let chunks: &[[_; 0]] = slice.as_chunks_unchecked() // Zero-length chunks are never allowed
🔬 This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, starting at the beginning of the slice, and a remainder slice with length strictly less than N.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(slice_as_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let (chunks, remainder) = slice.as_chunks();
assert_eq!(chunks, &[['l', 'o'], ['r', 'e']]);
assert_eq!(remainder, &['m']);
🔬 This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, starting at the end of the slice, and a remainder slice with length strictly less than N.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(slice_as_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let (remainder, chunks) = slice.as_rchunks();
assert_eq!(remainder, &['l']);
assert_eq!(chunks, &[['o', 'r'], ['e', 'm']]);
🔬 This is a nightly-only experimental API. (array_chunks)

Returns an iterator over N elements of the slice at a time, starting at the beginning of the slice.

The chunks are array references and do not overlap. If N does not divide the length of the slice, then the last up to N-1 elements will be omitted and can be retrieved from the remainder function of the iterator.

This method is the const generic equivalent of chunks_exact.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(array_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.array_chunks();
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['m']);
🔬 This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.

Safety

This may only be called when

  • The slice splits exactly into N-element chunks (aka self.len() % N == 0).
  • N != 0.
Examples
#![feature(slice_as_chunks)]
let slice: &mut [char] = &mut ['l', 'o', 'r', 'e', 'm', '!'];
let chunks: &mut [[char; 1]] =
    // SAFETY: 1-element chunks never have remainder
    unsafe { slice.as_chunks_unchecked_mut() };
chunks[0] = ['L'];
assert_eq!(chunks, &[['L'], ['o'], ['r'], ['e'], ['m'], ['!']]);
let chunks: &mut [[char; 3]] =
    // SAFETY: The slice length (6) is a multiple of 3
    unsafe { slice.as_chunks_unchecked_mut() };
chunks[1] = ['a', 'x', '?'];
assert_eq!(slice, &['L', 'o', 'r', 'a', 'x', '?']);

// These would be unsound:
// let chunks: &[[_; 5]] = slice.as_chunks_unchecked_mut() // The slice length is not a multiple of 5
// let chunks: &[[_; 0]] = slice.as_chunks_unchecked_mut() // Zero-length chunks are never allowed
🔬 This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, starting at the beginning of the slice, and a remainder slice with length strictly less than N.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(slice_as_chunks)]
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

let (chunks, remainder) = v.as_chunks_mut();
remainder[0] = 9;
for chunk in chunks {
    *chunk = [count; 2];
    count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 9]);
🔬 This is a nightly-only experimental API. (slice_as_chunks)

Splits the slice into a slice of N-element arrays, starting at the end of the slice, and a remainder slice with length strictly less than N.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(slice_as_chunks)]
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

let (remainder, chunks) = v.as_rchunks_mut();
remainder[0] = 9;
for chunk in chunks {
    *chunk = [count; 2];
    count += 1;
}
assert_eq!(v, &[9, 1, 1, 2, 2]);
🔬 This is a nightly-only experimental API. (array_chunks)

Returns an iterator over N elements of the slice at a time, starting at the beginning of the slice.

The chunks are mutable array references and do not overlap. If N does not divide the length of the slice, then the last up to N-1 elements will be omitted and can be retrieved from the into_remainder function of the iterator.

This method is the const generic equivalent of chunks_exact_mut.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(array_chunks)]
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

for chunk in v.array_chunks_mut() {
    *chunk = [count; 2];
    count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 0]);
🔬 This is a nightly-only experimental API. (array_windows)

Returns an iterator over overlapping windows of N elements of a slice, starting at the beginning of the slice.

This is the const generic equivalent of windows.

If N is greater than the size of the slice, it will return no windows.

Panics

Panics if N is 0. This check will most probably get changed to a compile time error before this method gets stabilized.

Examples
#![feature(array_windows)]
let slice = [0, 1, 2, 3];
let mut iter = slice.array_windows();
assert_eq!(iter.next().unwrap(), &[0, 1]);
assert_eq!(iter.next().unwrap(), &[1, 2]);
assert_eq!(iter.next().unwrap(), &[2, 3]);
assert!(iter.next().is_none());

Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.

The chunks are 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.

See rchunks_exact for a variant of this iterator that returns chunks of always exactly chunk_size elements, and chunks for the same iterator but starting at the beginning of the slice.

Panics

Panics if chunk_size is 0.

Examples
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.rchunks(2);
assert_eq!(iter.next().unwrap(), &['e', 'm']);
assert_eq!(iter.next().unwrap(), &['o', 'r']);
assert_eq!(iter.next().unwrap(), &['l']);
assert!(iter.next().is_none());

Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.

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.

See rchunks_exact_mut for a variant of this iterator that returns chunks of always exactly chunk_size elements, and chunks_mut for the same iterator but starting at the beginning of the slice.

Panics

Panics if chunk_size is 0.

Examples
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

for chunk in v.rchunks_mut(2) {
    for elem in chunk.iter_mut() {
        *elem += count;
    }
    count += 1;
}
assert_eq!(v, &[3, 2, 2, 1, 1]);

Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.

The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted and can be retrieved from the remainder function of the iterator.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks.

See rchunks for a variant of this iterator that also returns the remainder as a smaller chunk, and chunks_exact for the same iterator but starting at the beginning of the slice.

Panics

Panics if chunk_size is 0.

Examples
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.rchunks_exact(2);
assert_eq!(iter.next().unwrap(), &['e', 'm']);
assert_eq!(iter.next().unwrap(), &['o', 'r']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['l']);

Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.

The chunks are mutable slices, and do not overlap. If chunk_size does not divide the length of the slice, then the last up to chunk_size-1 elements will be omitted and can be retrieved from the into_remainder function of the iterator.

Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks_mut.

See rchunks_mut for a variant of this iterator that also returns the remainder as a smaller chunk, and chunks_exact_mut for the same iterator but starting at the beginning of the slice.

Panics

Panics if chunk_size is 0.

Examples
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;

for chunk in v.rchunks_exact_mut(2) {
    for elem in chunk.iter_mut() {
        *elem += count;
    }
    count += 1;
}
assert_eq!(v, &[0, 2, 2, 1, 1]);
🔬 This is a nightly-only experimental API. (slice_group_by)

Returns an iterator over the slice producing non-overlapping runs of elements using the predicate to separate them.

The predicate is called on two elements following themselves, it means the predicate is called on slice[0] and slice[1] then on slice[1] and slice[2] and so on.

Examples
#![feature(slice_group_by)]

let slice = &[1, 1, 1, 3, 3, 2, 2, 2];

let mut iter = slice.group_by(|a, b| a == b);

assert_eq!(iter.next(), Some(&[1, 1, 1][..]));
assert_eq!(iter.next(), Some(&[3, 3][..]));
assert_eq!(iter.next(), Some(&[2, 2, 2][..]));
assert_eq!(iter.next(), None);

This method can be used to extract the sorted subslices:

#![feature(slice_group_by)]

let slice = &[1, 1, 2, 3, 2, 3, 2, 3, 4];

let mut iter = slice.group_by(|a, b| a <= b);

assert_eq!(iter.next(), Some(&[1, 1, 2, 3][..]));
assert_eq!(iter.next(), Some(&[2, 3][..]));
assert_eq!(iter.next(), Some(&[2, 3, 4][..]));
assert_eq!(iter.next(), None);
🔬 This is a nightly-only experimental API. (slice_group_by)

Returns an iterator over the slice producing non-overlapping mutable runs of elements using the predicate to separate them.

The predicate is called on two elements following themselves, it means the predicate is called on slice[0] and slice[1] then on slice[1] and slice[2] and so on.

Examples
#![feature(slice_group_by)]

let slice = &mut [1, 1, 1, 3, 3, 2, 2, 2];

let mut iter = slice.group_by_mut(|a, b| a == b);

assert_eq!(iter.next(), Some(&mut [1, 1, 1][..]));
assert_eq!(iter.next(), Some(&mut [3, 3][..]));
assert_eq!(iter.next(), Some(&mut [2, 2, 2][..]));
assert_eq!(iter.next(), None);

This method can be used to extract the sorted subslices:

#![feature(slice_group_by)]

let slice = &mut [1, 1, 2, 3, 2, 3, 2, 3, 4];

let mut iter = slice.group_by_mut(|a, b| a <= b);

assert_eq!(iter.next(), Some(&mut [1, 1, 2, 3][..]));
assert_eq!(iter.next(), Some(&mut [2, 3][..]));
assert_eq!(iter.next(), Some(&mut [2, 3, 4][..]));
assert_eq!(iter.next(), None);

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

{
   let (left, right) = v.split_at(0);
   assert_eq!(left, []);
   assert_eq!(right, [1, 2, 3, 4, 5, 6]);
}

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

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

Divides one mutable 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
let mut v = [1, 0, 3, 0, 5, 6];
let (left, right) = v.split_at_mut(2);
assert_eq!(left, [1, 0]);
assert_eq!(right, [3, 0, 5, 6]);
left[1] = 2;
right[1] = 4;
assert_eq!(v, [1, 2, 3, 4, 5, 6]);
🔬 This is a nightly-only experimental API. (slice_split_at_unchecked)

Divides one slice into two at an index, without doing bounds checking.

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).

For a safe alternative see split_at.

Safety

Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used. The caller has to ensure that 0 <= mid <= self.len().

Examples
#![feature(slice_split_at_unchecked)]

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

unsafe {
   let (left, right) = v.split_at_unchecked(0);
   assert_eq!(left, []);
   assert_eq!(right, [1, 2, 3, 4, 5, 6]);
}

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

unsafe {
    let (left, right) = v.split_at_unchecked(6);
    assert_eq!(left, [1, 2, 3, 4, 5, 6]);
    assert_eq!(right, []);
}
🔬 This is a nightly-only experimental API. (slice_split_at_unchecked)

Divides one mutable slice into two at an index, without doing bounds checking.

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).

For a safe alternative see split_at_mut.

Safety

Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used. The caller has to ensure that 0 <= mid <= self.len().

Examples
#![feature(slice_split_at_unchecked)]

let mut v = [1, 0, 3, 0, 5, 6];
// scoped to restrict the lifetime of the borrows
unsafe {
    let (left, right) = v.split_at_mut_unchecked(2);
    assert_eq!(left, [1, 0]);
    assert_eq!(right, [3, 0, 5, 6]);
    left[1] = 2;
    right[1] = 4;
}
assert_eq!(v, [1, 2, 3, 4, 5, 6]);
🔬 This is a nightly-only experimental API. (split_array)

Divides one slice into an array and a remainder slice at an index.

The array will contain all indices from [0, N) (excluding the index N itself) and the slice will contain all indices from [N, len) (excluding the index len itself).

Panics

Panics if N > len.

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, []);
}
🔬 This is a nightly-only experimental API. (split_array)

Divides one mutable slice into an array and a remainder slice at an index.

The array will contain all indices from [0, N) (excluding the index N itself) and the slice will contain all indices from [N, len) (excluding the index len itself).

Panics

Panics if N > len.

Examples
#![feature(split_array)]

let mut v = &mut [1, 0, 3, 0, 5, 6][..];
let (left, right) = v.split_array_mut::<2>();
assert_eq!(left, &mut [1, 0]);
assert_eq!(right, [3, 0, 5, 6]);
left[1] = 2;
right[1] = 4;
assert_eq!(v, [1, 2, 3, 4, 5, 6]);
🔬 This is a nightly-only experimental API. (split_array)

Divides one slice into an array and a remainder slice at an index from the end.

The slice will contain all indices from [0, len - N) (excluding the index len - N itself) and the array will contain all indices from [len - N, len) (excluding the index len itself).

Panics

Panics if N > len.

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]);
}
🔬 This is a nightly-only experimental API. (split_array)

Divides one mutable slice into an array and a remainder slice at an index from the end.

The slice will contain all indices from [0, len - N) (excluding the index N itself) and the array will contain all indices from [len - N, len) (excluding the index len itself).

Panics

Panics if N > len.

Examples
#![feature(split_array)]

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

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

Examples
let slice = [10, 40, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

If the first element is matched, an empty slice will be the first item returned by the iterator. Similarly, if the last element in the slice is matched, an empty slice will be the last item returned by the iterator:

let slice = [10, 40, 33];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40]);
assert_eq!(iter.next().unwrap(), &[]);
assert!(iter.next().is_none());

If two matched elements are directly adjacent, an empty slice will be present between them:

let slice = [10, 6, 33, 20];
let mut iter = slice.split(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10]);
assert_eq!(iter.next().unwrap(), &[]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

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

Examples
let mut v = [10, 40, 30, 20, 60, 50];

for group in v.split_mut(|num| *num % 3 == 0) {
    group[0] = 1;
}
assert_eq!(v, [1, 40, 30, 1, 60, 1]);

Returns an iterator over subslices separated by elements that match pred. The matched element is contained in the end of the previous subslice as a terminator.

Examples
let slice = [10, 40, 33, 20];
let mut iter = slice.split_inclusive(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[10, 40, 33]);
assert_eq!(iter.next().unwrap(), &[20]);
assert!(iter.next().is_none());

If the last element of the slice is matched, that element will be considered the terminator of the preceding slice. That slice will be the last item returned by the iterator.

let slice = [3, 10, 40, 33];
let mut iter = slice.split_inclusive(|num| num % 3 == 0);

assert_eq!(iter.next().unwrap(), &[3]);
assert_eq!(iter.next().unwrap(), &[10, 40, 33]);
assert!(iter.next().is_none());

Returns an iterator over mutable subslices separated by elements that match pred. The matched element is contained in the previous subslice as a terminator.

Examples
let mut v = [10, 40, 30, 20, 60, 50];

for group in v.split_inclusive_mut(|num| *num % 3 == 0) {
    let terminator_idx = group.len()-1;
    group[terminator_idx] = 1;
}
assert_eq!(v, [10, 40, 1, 20, 1, 1]);

Returns an iterator over subslices separated by elements that match pred, starting at the end of the slice and working backwards. The matched element is not contained in the subslices.

Examples
let slice = [11, 22, 33, 0, 44, 55];
let mut iter = slice.rsplit(|num| *num == 0);

assert_eq!(iter.next().unwrap(), &[44, 55]);
assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
assert_eq!(iter.next(), None);

As with split(), if the first or last element is matched, an empty slice will be the first (or last) item returned by the iterator.

let v = &[0, 1, 1, 2, 3, 5, 8];
let mut it = v.rsplit(|n| *n % 2 == 0);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next().unwrap(), &[3, 5]);
assert_eq!(it.next().unwrap(), &[1, 1]);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next(), None);

Returns an iterator over mutable subslices separated by elements that match pred, starting at the end of the slice and working backwards. The matched element is not contained in the subslices.

Examples
let mut v = [100, 400, 300, 200, 600, 500];

let mut count = 0;
for group in v.rsplit_mut(|num| *num % 3 == 0) {
    count += 1;
    group[0] = count;
}
assert_eq!(v, [3, 400, 300, 2, 600, 1]);

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]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.splitn(2, |num| *num % 3 == 0) {
    println!("{group:?}");
}

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
let mut v = [10, 40, 30, 20, 60, 50];

for group in v.splitn_mut(2, |num| *num % 3 == 0) {
    group[0] = 1;
}
assert_eq!(v, [1, 40, 30, 1, 60, 50]);

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]):

let v = [10, 40, 30, 20, 60, 50];

for group in v.rsplitn(2, |num| *num % 3 == 0) {
    println!("{group:?}");
}

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
let mut s = [10, 40, 30, 20, 60, 50];

for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
    group[0] = 1;
}
assert_eq!(s, [1, 40, 30, 20, 60, 1]);

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

This operation is O(n).

Note that if you have a sorted slice, binary_search may be faster.

Examples
let v = [10, 40, 30];
assert!(v.contains(&30));
assert!(!v.contains(&50));

If you do not have a &T, but some other value that you can compare with one (for example, String implements PartialEq<str>), you can use iter().any:

let v = [String::from("hello"), String::from("world")]; // slice of `String`
assert!(v.iter().any(|e| e == "hello")); // search with `&str`
assert!(!v.iter().any(|e| e == "hi"));

Returns true if needle is a prefix of the slice.

Examples
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]));

Always returns true if needle is an empty slice:

let v = &[10, 40, 30];
assert!(v.starts_with(&[]));
let v: &[u8] = &[];
assert!(v.starts_with(&[]));

Returns true if needle is a suffix of the slice.

Examples
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]));

Always returns true if needle is an empty slice:

let v = &[10, 40, 30];
assert!(v.ends_with(&[]));
let v: &[u8] = &[];
assert!(v.ends_with(&[]));

Returns a subslice with the prefix removed.

If the slice starts with prefix, returns the subslice after the prefix, wrapped in Some. If prefix is empty, simply returns the original slice.

If the slice does not start with prefix, returns None.

Examples
let v = &[10, 40, 30];
assert_eq!(v.strip_prefix(&[10]), Some(&[40, 30][..]));
assert_eq!(v.strip_prefix(&[10, 40]), Some(&[30][..]));
assert_eq!(v.strip_prefix(&[50]), None);
assert_eq!(v.strip_prefix(&[10, 50]), None);

let prefix : &str = "he";
assert_eq!(b"hello".strip_prefix(prefix.as_bytes()),
           Some(b"llo".as_ref()));

Returns a subslice with the suffix removed.

If the slice ends with suffix, returns the subslice before the suffix, wrapped in Some. If suffix is empty, simply returns the original slice.

If the slice does not end with suffix, returns None.

Examples
let v = &[10, 40, 30];
assert_eq!(v.strip_suffix(&[30]), Some(&[10, 40][..]));
assert_eq!(v.strip_suffix(&[40, 30]), Some(&[10][..]));
assert_eq!(v.strip_suffix(&[50]), None);
assert_eq!(v.strip_suffix(&[50, 30]), None);

Binary searches this slice for a given element. This behaves similary to contains if this slice is sorted.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. The index is chosen deterministically, but is subject to change in future versions of Rust. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

See also binary_search_by, binary_search_by_key, and partition_point.

Examples

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].

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, });

If you want to insert an item to a sorted vector, while maintaining sort order, consider using partition_point:

let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
let num = 42;
let idx = s.partition_point(|&x| x < num);
// The above is equivalent to `let idx = s.binary_search(&num).unwrap_or_else(|x| x);`
s.insert(idx, num);
assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);

Binary searches this slice with a comparator function. This behaves similarly to contains if this slice is sorted.

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 the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. The index is chosen deterministically, but is subject to change in future versions of Rust. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

See also binary_search, binary_search_by_key, and partition_point.

Examples

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].

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, });

Binary searches this slice with a key extraction function. This behaves similarly to contains if this slice is sorted.

Assumes that the slice is sorted by the key, for instance with sort_by_key using the same key extraction function.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. The index is chosen deterministically, but is subject to change in future versions of Rust. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

See also binary_search, binary_search_by, and partition_point.

Examples

Looks up a series of four elements in a slice of pairs sorted by their second 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].

let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
         (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
         (1, 21), (2, 34), (4, 55)];

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

Sorts the slice, but might not preserve the order of equal elements.

This sort is unstable (i.e., may reorder equal elements), in-place (i.e., does not allocate), and O(n * log(n)) worst-case.

Current implementation

The current algorithm is based on pattern-defeating quicksort by Orson Peters, which combines the fast average case of randomized quicksort with the fast worst case of heapsort, while achieving linear time on slices with certain patterns. It uses some randomization to avoid degenerate cases, but with a fixed seed to always provide deterministic behavior.

It is typically faster than stable sorting, except in a few special cases, e.g., when the slice consists of several concatenated sorted sequences.

Examples
let mut v = [-5, 4, 1, -3, 2];

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

Sorts the slice with a comparator function, but might not preserve the order of equal elements.

This sort is unstable (i.e., may reorder equal elements), in-place (i.e., does not allocate), and O(n * log(n)) worst-case.

The comparator function must define a total ordering for the elements in the slice. If the ordering is not total, the order of the elements is unspecified. An order is a total order if it is (for all a, b and c):

  • total and antisymmetric: exactly one of a < b, a == b or a > b is true, and
  • transitive, a < b and b < c implies a < c. The same must hold for both == and >.

For example, while f64 doesn’t implement Ord because NaN != NaN, we can use partial_cmp as our sort function when we know the slice doesn’t contain a NaN.

let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0];
floats.sort_unstable_by(|a, b| a.partial_cmp(b).unwrap());
assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]);
Current implementation

The current algorithm is based on pattern-defeating quicksort by Orson Peters, which combines the fast average case of randomized quicksort with the fast worst case of heapsort, while achieving linear time on slices with certain patterns. It uses some randomization to avoid degenerate cases, but with a fixed seed to always provide deterministic behavior.

It is typically faster than stable sorting, except in a few special cases, e.g., when the slice consists of several concatenated sorted sequences.

Examples
let mut v = [5, 4, 1, 3, 2];
v.sort_unstable_by(|a, b| a.cmp(b));
assert!(v == [1, 2, 3, 4, 5]);

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

Sorts the slice with a key extraction function, but might not preserve the order of equal elements.

This sort is unstable (i.e., may reorder equal elements), in-place (i.e., does not allocate), and O(m * n * log(n)) worst-case, where the key function is O(m).

Current implementation

The current algorithm is based on pattern-defeating quicksort by Orson Peters, which combines the fast average case of randomized quicksort with the fast worst case of heapsort, while achieving linear time on slices with certain patterns. It uses some randomization to avoid degenerate cases, but with a fixed seed to always provide deterministic behavior.

Due to its key calling strategy, sort_unstable_by_key is likely to be slower than sort_by_cached_key in cases where the key function is expensive.

Examples
let mut v = [-5i32, 4, 1, -3, 2];

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

Reorder the slice such that the element at index is at its final sorted position.

This reordering has the additional property that any value at position i < index will be less than or equal to any value at a position j > index. Additionally, this reordering is unstable (i.e. any number of equal elements may end up at position index), in-place (i.e. does not allocate), and O(n) worst-case. This function is also/ known as “kth element” in other libraries. It returns a triplet of the following values: all elements less than the one at the given index, the value at the given index, and all elements greater than the one at the given index.

Current implementation

The current algorithm is based on the quickselect portion of the same quicksort algorithm used for sort_unstable.

Panics

Panics when index >= len(), meaning it always panics on empty slices.

Examples
let mut v = [-5i32, 4, 1, -3, 2];

// Find the median
v.select_nth_unstable(2);

// We are only guaranteed the slice will be one of the following, based on the way we sort
// about the specified index.
assert!(v == [-3, -5, 1, 2, 4] ||
        v == [-5, -3, 1, 2, 4] ||
        v == [-3, -5, 1, 4, 2] ||
        v == [-5, -3, 1, 4, 2]);

Reorder the slice with a comparator function such that the element at index is at its final sorted position.

This reordering has the additional property that any value at position i < index will be less than or equal to any value at a position j > index using the comparator function. Additionally, this reordering is unstable (i.e. any number of equal elements may end up at position index), in-place (i.e. does not allocate), and O(n) worst-case. This function is also known as “kth element” in other libraries. It returns a triplet of the following values: all elements less than the one at the given index, the value at the given index, and all elements greater than the one at the given index, using the provided comparator function.

Current implementation

The current algorithm is based on the quickselect portion of the same quicksort algorithm used for sort_unstable.

Panics

Panics when index >= len(), meaning it always panics on empty slices.

Examples
let mut v = [-5i32, 4, 1, -3, 2];

// Find the median as if the slice were sorted in descending order.
v.select_nth_unstable_by(2, |a, b| b.cmp(a));

// We are only guaranteed the slice will be one of the following, based on the way we sort
// about the specified index.
assert!(v == [2, 4, 1, -5, -3] ||
        v == [2, 4, 1, -3, -5] ||
        v == [4, 2, 1, -5, -3] ||
        v == [4, 2, 1, -3, -5]);

Reorder the slice with a key extraction function such that the element at index is at its final sorted position.

This reordering has the additional property that any value at position i < index will be less than or equal to any value at a position j > index using the key extraction function. Additionally, this reordering is unstable (i.e. any number of equal elements may end up at position index), in-place (i.e. does not allocate), and O(n) worst-case. This function is also known as “kth element” in other libraries. It returns a triplet of the following values: all elements less than the one at the given index, the value at the given index, and all elements greater than the one at the given index, using the provided key extraction function.

Current implementation

The current algorithm is based on the quickselect portion of the same quicksort algorithm used for sort_unstable.

Panics

Panics when index >= len(), meaning it always panics on empty slices.

Examples
let mut v = [-5i32, 4, 1, -3, 2];

// Return the median as if the array were sorted according to absolute value.
v.select_nth_unstable_by_key(2, |a| a.abs());

// We are only guaranteed the slice will be one of the following, based on the way we sort
// about the specified index.
assert!(v == [1, 2, -3, 4, -5] ||
        v == [1, 2, -3, -5, 4] ||
        v == [2, 1, -3, 4, -5] ||
        v == [2, 1, -3, -5, 4]);
🔬 This is a nightly-only experimental API. (slice_partition_dedup)

Moves all consecutive repeated elements to the end of the slice according to the PartialEq trait implementation.

Returns two slices. The first contains no consecutive repeated elements. The second contains all the duplicates in no specified order.

If the slice is sorted, the first returned slice contains no duplicates.

Examples
#![feature(slice_partition_dedup)]

let mut slice = [1, 2, 2, 3, 3, 2, 1, 1];

let (dedup, duplicates) = slice.partition_dedup();

assert_eq!(dedup, [1, 2, 3, 2, 1]);
assert_eq!(duplicates, [2, 3, 1]);
🔬 This is a nightly-only experimental API. (slice_partition_dedup)

Moves all but the first of consecutive elements to the end of the slice satisfying a given equality relation.

Returns two slices. The first contains no consecutive repeated elements. The second contains all the duplicates in no specified order.

The same_bucket function is passed references to two elements from the slice and must determine if the elements compare equal. The elements are passed in opposite order from their order in the slice, so if same_bucket(a, b) returns true, a is moved at the end of the slice.

If the slice is sorted, the first returned slice contains no duplicates.

Examples
#![feature(slice_partition_dedup)]

let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"];

let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b));

assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]);
assert_eq!(duplicates, ["bar", "Foo", "BAZ"]);
🔬 This is a nightly-only experimental API. (slice_partition_dedup)

Moves all but the first of consecutive elements to the end of the slice that resolve to the same key.

Returns two slices. The first contains no consecutive repeated elements. The second contains all the duplicates in no specified order.

If the slice is sorted, the first returned slice contains no duplicates.

Examples
#![feature(slice_partition_dedup)]

let mut slice = [10, 20, 21, 30, 30, 20, 11, 13];

let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10);

assert_eq!(dedup, [10, 20, 30, 20, 11]);
assert_eq!(duplicates, [21, 30, 13]);

Rotates the slice in-place such that the first mid elements of the slice move to the end while the last self.len() - mid elements move to the front. After calling rotate_left, the element previously at index mid will become the first element in the slice.

Panics

This function will panic if mid is greater than the length of the slice. Note that mid == self.len() does not panic and is a no-op rotation.

Complexity

Takes linear (in self.len()) time.

Examples
let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
a.rotate_left(2);
assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);

Rotating a subslice:

let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
a[1..5].rotate_left(1);
assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);

Rotates the slice in-place such that the first self.len() - k elements of the slice move to the end while the last k elements move to the front. After calling rotate_right, the element previously at index self.len() - k will become the first element in the slice.

Panics

This function will panic if k is greater than the length of the slice. Note that k == self.len() does not panic and is a no-op rotation.

Complexity

Takes linear (in self.len()) time.

Examples
let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
a.rotate_right(2);
assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);

Rotate a subslice:

let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
a[1..5].rotate_right(1);
assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);

Fills self with elements by cloning value.

Examples
let mut buf = vec![0; 10];
buf.fill(1);
assert_eq!(buf, vec![1; 10]);

Fills self with elements returned by calling a closure repeatedly.

This method uses a closure to create new values. If you’d rather Clone a given value, use fill. If you want to use the Default trait to generate values, you can pass Default::default as the argument.

Examples
let mut buf = vec![1; 10];
buf.fill_with(Default::default);
assert_eq!(buf, vec![0; 10]);

Copies the elements from src into self.

The length of src must be the same as self.

Panics

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

Examples

Cloning two elements from a slice into another:

let src = [1, 2, 3, 4];
let mut dst = [0, 0];

// Because the slices have to be the same length,
// we slice the source slice from four elements
// to two. It will panic if we don't do this.
dst.clone_from_slice(&src[2..]);

assert_eq!(src, [1, 2, 3, 4]);
assert_eq!(dst, [3, 4]);

Rust enforces that there can only be one mutable reference with no immutable references to a particular piece of data in a particular scope. Because of this, attempting to use clone_from_slice on a single slice will result in a compile failure:

ⓘ
let mut slice = [1, 2, 3, 4, 5];

slice[..2].clone_from_slice(&slice[3..]); // compile fail!

To work around this, we can use split_at_mut to create two distinct sub-slices from a slice:

let mut slice = [1, 2, 3, 4, 5];

{
    let (left, right) = slice.split_at_mut(2);
    left.clone_from_slice(&right[1..]);
}

assert_eq!(slice, [4, 5, 3, 4, 5]);

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

The length of src must be the same as self.

If T does not implement Copy, use clone_from_slice.

Panics

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

Examples

Copying two elements from a slice into another:

let src = [1, 2, 3, 4];
let mut dst = [0, 0];

// Because the slices have to be the same length,
// we slice the source slice from four elements
// to two. It will panic if we don't do this.
dst.copy_from_slice(&src[2..]);

assert_eq!(src, [1, 2, 3, 4]);
assert_eq!(dst, [3, 4]);

Rust enforces that there can only be one mutable reference with no immutable references to a particular piece of data in a particular scope. Because of this, attempting to use copy_from_slice on a single slice will result in a compile failure:

ⓘ
let mut slice = [1, 2, 3, 4, 5];

slice[..2].copy_from_slice(&slice[3..]); // compile fail!

To work around this, we can use split_at_mut to create two distinct sub-slices from a slice:

let mut slice = [1, 2, 3, 4, 5];

{
    let (left, right) = slice.split_at_mut(2);
    left.copy_from_slice(&right[1..]);
}

assert_eq!(slice, [4, 5, 3, 4, 5]);

Copies elements from one part of the slice to another part of itself, using a memmove.

src is the range within self to copy from. dest is the starting index of the range within self to copy to, which will have the same length as src. The two ranges may overlap. The ends of the two ranges must be less than or equal to self.len().

Panics

This function will panic if either range exceeds the end of the slice, or if the end of src is before the start.

Examples

Copying four bytes within a slice:

let mut bytes = *b"Hello, World!";

bytes.copy_within(1..5, 8);

assert_eq!(&bytes, b"Hello, Wello!");

Swaps all elements in self with those in other.

The length of other must be the same as self.

Panics

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

Example

Swapping two elements across slices:

let mut slice1 = [0, 0];
let mut slice2 = [1, 2, 3, 4];

slice1.swap_with_slice(&mut slice2[2..]);

assert_eq!(slice1, [3, 4]);
assert_eq!(slice2, [1, 2, 0, 0]);

Rust enforces that there can only be one mutable reference to a particular piece of data in a particular scope. Because of this, attempting to use swap_with_slice on a single slice will result in a compile failure:

ⓘ
let mut slice = [1, 2, 3, 4, 5];
slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!

To work around this, we can use split_at_mut to create two distinct mutable sub-slices from a slice:

let mut slice = [1, 2, 3, 4, 5];

{
    let (left, right) = slice.split_at_mut(2);
    left.swap_with_slice(&mut right[1..]);
}

assert_eq!(slice, [4, 5, 3, 1, 2]);

Transmute the slice to a slice of another type, ensuring alignment of the types is maintained.

This method splits the slice into three distinct slices: prefix, correctly aligned middle slice of a new type, and the suffix slice. The method may make the middle slice the greatest length possible for a given type and input slice, but only your algorithm’s performance should depend on that, not its correctness. It is permissible for all of the input data to be returned as the prefix or suffix slice.

This method has no purpose when either input element T or output element U are zero-sized and will return the original slice without splitting anything.

Safety

This method is essentially a transmute with respect to the elements in the returned middle slice, so all the usual caveats pertaining to transmute::<T, U> also apply here.

Examples

Basic usage:

unsafe {
    let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
    let (prefix, shorts, suffix) = bytes.align_to::<u16>();
    // less_efficient_algorithm_for_bytes(prefix);
    // more_efficient_algorithm_for_aligned_shorts(shorts);
    // less_efficient_algorithm_for_bytes(suffix);
}

Transmute the slice to a slice of another type, ensuring alignment of the types is maintained.

This method splits the slice into three distinct slices: prefix, correctly aligned middle slice of a new type, and the suffix slice. The method may make the middle slice the greatest length possible for a given type and input slice, but only your algorithm’s performance should depend on that, not its correctness. It is permissible for all of the input data to be returned as the prefix or suffix slice.

This method has no purpose when either input element T or output element U are zero-sized and will return the original slice without splitting anything.

Safety

This method is essentially a transmute with respect to the elements in the returned middle slice, so all the usual caveats pertaining to transmute::<T, U> also apply here.

Examples

Basic usage:

unsafe {
    let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
    let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
    // less_efficient_algorithm_for_bytes(prefix);
    // more_efficient_algorithm_for_aligned_shorts(shorts);
    // less_efficient_algorithm_for_bytes(suffix);
}
🔬 This is a nightly-only experimental API. (portable_simd)

Split a slice into a prefix, a middle of aligned SIMD types, and a suffix.

This is a safe wrapper around slice::align_to, so has the same weak postconditions as that method. You’re only assured that self.len() == prefix.len() + middle.len() * LANES + suffix.len().

Notably, all of the following are possible:

  • prefix.len() >= LANES.
  • middle.is_empty() despite self.len() >= 3 * LANES.
  • suffix.len() >= LANES.

That said, this is a safe method, so if you’re only writing safe code, then this can at most cause incorrect logic, not unsoundness.

Panics

This will panic if the size of the SIMD type is different from LANES times that of the scalar.

At the time of writing, the trait restrictions on Simd<T, LANES> keeps that from ever happening, as only power-of-two numbers of lanes are supported. It’s possible that, in the future, those restrictions might be lifted in a way that would make it possible to see panics from this method for something like LANES == 3.

Examples
#![feature(portable_simd)]

let short = &[1, 2, 3];
let (prefix, middle, suffix) = short.as_simd::<4>();
assert_eq!(middle, []); // Not enough elements for anything in the middle

// They might be split in any possible way between prefix and suffix
let it = prefix.iter().chain(suffix).copied();
assert_eq!(it.collect::<Vec<_>>(), vec![1, 2, 3]);

fn basic_simd_sum(x: &[f32]) -> f32 {
    use std::ops::Add;
    use std::simd::f32x4;
    let (prefix, middle, suffix) = x.as_simd();
    let sums = f32x4::from_array([
        prefix.iter().copied().sum(),
        0.0,
        0.0,
        suffix.iter().copied().sum(),
    ]);
    let sums = middle.iter().copied().fold(sums, f32x4::add);
    sums.reduce_sum()
}

let numbers: Vec<f32> = (1..101).map(|x| x as _).collect();
assert_eq!(basic_simd_sum(&numbers[1..99]), 4949.0);
🔬 This is a nightly-only experimental API. (portable_simd)

Split a slice into a prefix, a middle of aligned SIMD types, and a suffix.

This is a safe wrapper around slice::align_to_mut, so has the same weak postconditions as that method. You’re only assured that self.len() == prefix.len() + middle.len() * LANES + suffix.len().

Notably, all of the following are possible:

  • prefix.len() >= LANES.
  • middle.is_empty() despite self.len() >= 3 * LANES.
  • suffix.len() >= LANES.

That said, this is a safe method, so if you’re only writing safe code, then this can at most cause incorrect logic, not unsoundness.

This is the mutable version of slice::as_simd; see that for examples.

Panics

This will panic if the size of the SIMD type is different from LANES times that of the scalar.

At the time of writing, the trait restrictions on Simd<T, LANES> keeps that from ever happening, as only power-of-two numbers of lanes are supported. It’s possible that, in the future, those restrictions might be lifted in a way that would make it possible to see panics from this method for something like LANES == 3.

🔬 This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this slice are sorted.

That is, for each element a and its following element b, a <= b must hold. If the slice yields exactly zero or one element, true is returned.

Note that if Self::Item is only PartialOrd, but not Ord, the above definition implies that this function returns false if any two consecutive items are not comparable.

Examples
#![feature(is_sorted)]
let empty: [i32; 0] = [];

assert!([1, 2, 2, 9].is_sorted());
assert!(![1, 3, 2, 4].is_sorted());
assert!([0].is_sorted());
assert!(empty.is_sorted());
assert!(![0.0, 1.0, f32::NAN].is_sorted());
🔬 This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this slice are sorted using the given comparator function.

Instead of using PartialOrd::partial_cmp, this function uses the given compare function to determine the ordering of two elements. Apart from that, it’s equivalent to is_sorted; see its documentation for more information.

🔬 This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this slice are sorted using the given key extraction function.

Instead of comparing the slice’s elements directly, this function compares the keys of the elements, as determined by f. Apart from that, it’s equivalent to is_sorted; see its documentation for more information.

Examples
#![feature(is_sorted)]

assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len()));
assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));

Returns the index of the partition point according to the given predicate (the index of the first element of the second partition).

The slice is assumed to be partitioned according to the given predicate. This means that all elements for which the predicate returns true are at the start of the slice and all elements for which the predicate returns false are at the end. For example, [7, 15, 3, 5, 4, 12, 6] is a partitioned under the predicate x % 2 != 0 (all odd numbers are at the start, all even at the end).

If this slice is not partitioned, the returned result is unspecified and meaningless, as this method performs a kind of binary search.

See also binary_search, binary_search_by, and binary_search_by_key.

Examples
let v = [1, 2, 3, 3, 5, 6, 7];
let i = v.partition_point(|&x| x < 5);

assert_eq!(i, 4);
assert!(v[..i].iter().all(|&x| x < 5));
assert!(v[i..].iter().all(|&x| !(x < 5)));

If you want to insert an item to a sorted vector, while maintaining sort order:

let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
let num = 42;
let idx = s.partition_point(|&x| x < num);
s.insert(idx, num);
assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
🔬 This is a nightly-only experimental API. (slice_take)

Removes the subslice corresponding to the given range and returns a reference to it.

Returns None and does not modify the slice if the given range is out of bounds.

Note that this method only accepts one-sided ranges such as 2.. or ..6, but not 2..6.

Examples

Taking the first three elements of a slice:

#![feature(slice_take)]

let mut slice: &[_] = &['a', 'b', 'c', 'd'];
let mut first_three = slice.take(..3).unwrap();

assert_eq!(slice, &['d']);
assert_eq!(first_three, &['a', 'b', 'c']);

Taking the last two elements of a slice:

#![feature(slice_take)]

let mut slice: &[_] = &['a', 'b', 'c', 'd'];
let mut tail = slice.take(2..).unwrap();

assert_eq!(slice, &['a', 'b']);
assert_eq!(tail, &['c', 'd']);

Getting None when range is out of bounds:

#![feature(slice_take)]

let mut slice: &[_] = &['a', 'b', 'c', 'd'];

assert_eq!(None, slice.take(5..));
assert_eq!(None, slice.take(..5));
assert_eq!(None, slice.take(..=4));
let expected: &[char] = &['a', 'b', 'c', 'd'];
assert_eq!(Some(expected), slice.take(..4));
🔬 This is a nightly-only experimental API. (slice_take)

Removes the subslice corresponding to the given range and returns a mutable reference to it.

Returns None and does not modify the slice if the given range is out of bounds.

Note that this method only accepts one-sided ranges such as 2.. or ..6, but not 2..6.

Examples

Taking the first three elements of a slice:

#![feature(slice_take)]

let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
let mut first_three = slice.take_mut(..3).unwrap();

assert_eq!(slice, &mut ['d']);
assert_eq!(first_three, &mut ['a', 'b', 'c']);

Taking the last two elements of a slice:

#![feature(slice_take)]

let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
let mut tail = slice.take_mut(2..).unwrap();

assert_eq!(slice, &mut ['a', 'b']);
assert_eq!(tail, &mut ['c', 'd']);

Getting None when range is out of bounds:

#![feature(slice_take)]

let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];

assert_eq!(None, slice.take_mut(5..));
assert_eq!(None, slice.take_mut(..5));
assert_eq!(None, slice.take_mut(..=4));
let expected: &mut [_] = &mut ['a', 'b', 'c', 'd'];
assert_eq!(Some(expected), slice.take_mut(..4));
🔬 This is a nightly-only experimental API. (slice_take)

Removes the first element of the slice and returns a reference to it.

Returns None if the slice is empty.

Examples
#![feature(slice_take)]

let mut slice: &[_] = &['a', 'b', 'c'];
let first = slice.take_first().unwrap();

assert_eq!(slice, &['b', 'c']);
assert_eq!(first, &'a');
🔬 This is a nightly-only experimental API. (slice_take)

Removes the first element of the slice and returns a mutable reference to it.

Returns None if the slice is empty.

Examples
#![feature(slice_take)]

let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
let first = slice.take_first_mut().unwrap();
*first = 'd';

assert_eq!(slice, &['b', 'c']);
assert_eq!(first, &'d');
🔬 This is a nightly-only experimental API. (slice_take)

Removes the last element of the slice and returns a reference to it.

Returns None if the slice is empty.

Examples
#![feature(slice_take)]

let mut slice: &[_] = &['a', 'b', 'c'];
let last = slice.take_last().unwrap();

assert_eq!(slice, &['a', 'b']);
assert_eq!(last, &'c');
🔬 This is a nightly-only experimental API. (slice_take)

Removes the last element of the slice and returns a mutable reference to it.

Returns None if the slice is empty.

Examples
#![feature(slice_take)]

let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
let last = slice.take_last_mut().unwrap();
*last = 'd';

assert_eq!(slice, &['a', 'b']);
assert_eq!(last, &'d');

Checks if all bytes in this slice are within the ASCII range.

Checks that two slices are an ASCII case-insensitive match.

Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.

Converts this slice to its ASCII upper case equivalent in-place.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use to_ascii_uppercase.

Converts this slice to its ASCII lower case equivalent in-place.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use to_ascii_lowercase.

Returns an iterator that produces an escaped version of this slice, treating it as an ASCII string.

Examples

let s = b"0\t\r\n'\"\\\x9d";
let escaped = s.escape_ascii().to_string();
assert_eq!(escaped, "0\\t\\r\\n\\'\\\"\\\\\\x9d");
🔬 This is a nightly-only experimental API. (byte_slice_trim_ascii)

Returns a byte slice with leading ASCII whitespace bytes removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples
#![feature(byte_slice_trim_ascii)]

assert_eq!(b" \t hello world\n".trim_ascii_start(), b"hello world\n");
assert_eq!(b"  ".trim_ascii_start(), b"");
assert_eq!(b"".trim_ascii_start(), b"");
🔬 This is a nightly-only experimental API. (byte_slice_trim_ascii)

Returns a byte slice with trailing ASCII whitespace bytes removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples
#![feature(byte_slice_trim_ascii)]

assert_eq!(b"\r hello world\n ".trim_ascii_end(), b"\r hello world");
assert_eq!(b"  ".trim_ascii_end(), b"");
assert_eq!(b"".trim_ascii_end(), b"");
🔬 This is a nightly-only experimental API. (byte_slice_trim_ascii)

Returns a byte slice with leading and trailing ASCII whitespace bytes removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples
#![feature(byte_slice_trim_ascii)]

assert_eq!(b"\r hello world\n ".trim_ascii(), b"hello world");
assert_eq!(b"  ".trim_ascii(), b"");
assert_eq!(b"".trim_ascii(), b"");

Sorts the slice.

This sort is stable (i.e., does not reorder equal elements) and O(n * log(n)) worst-case.

When applicable, unstable sorting is preferred because it is generally faster than stable sorting and it doesn’t allocate auxiliary memory. See sort_unstable.

Current implementation

The current algorithm is an adaptive, iterative merge sort inspired by timsort. It is designed to be very fast in cases where the slice is nearly sorted, or consists of two or more sorted sequences concatenated one after another.

Also, it allocates temporary storage half the size of self, but for short slices a non-allocating insertion sort is used instead.

Examples
let mut v = [-5, 4, 1, -3, 2];

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

Sorts the slice with a comparator function.

This sort is stable (i.e., does not reorder equal elements) and O(n * log(n)) worst-case.

The comparator function must define a total ordering for the elements in the slice. If the ordering is not total, the order of the elements is unspecified. An order is a total order if it is (for all a, b and c):

  • total and antisymmetric: exactly one of a < b, a == b or a > b is true, and
  • transitive, a < b and b < c implies a < c. The same must hold for both == and >.

For example, while f64 doesn’t implement Ord because NaN != NaN, we can use partial_cmp as our sort function when we know the slice doesn’t contain a NaN.

let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0];
floats.sort_by(|a, b| a.partial_cmp(b).unwrap());
assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]);

When applicable, unstable sorting is preferred because it is generally faster than stable sorting and it doesn’t allocate auxiliary memory. See sort_unstable_by.

Current implementation

The current algorithm is an adaptive, iterative merge sort inspired by timsort. It is designed to be very fast in cases where the slice is nearly sorted, or consists of two or more sorted sequences concatenated one after another.

Also, it allocates temporary storage half the size of self, but for short slices a non-allocating insertion sort is used instead.

Examples
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]);

Sorts the slice with a key extraction function.

This sort is stable (i.e., does not reorder equal elements) and O(m * n * log(n)) worst-case, where the key function is O(m).

For expensive key functions (e.g. functions that are not simple property accesses or basic operations), sort_by_cached_key is likely to be significantly faster, as it does not recompute element keys.

When applicable, unstable sorting is preferred because it is generally faster than stable sorting and it doesn’t allocate auxiliary memory. See sort_unstable_by_key.

Current implementation

The current algorithm is an adaptive, iterative merge sort inspired by timsort. It is designed to be very fast in cases where the slice is nearly sorted, or consists of two or more sorted sequences concatenated one after another.

Also, it allocates temporary storage half the size of self, but for short slices a non-allocating insertion sort is used instead.

Examples
let mut v = [-5i32, 4, 1, -3, 2];

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

Sorts the slice with a key extraction function.

During sorting, the key function is called at most once per element, by using temporary storage to remember the results of key evaluation. The order of calls to the key function is unspecified and may change in future versions of the standard library.

This sort is stable (i.e., does not reorder equal elements) and O(m * n + n * log(n)) worst-case, where the key function is O(m).

For simple key functions (e.g., functions that are property accesses or basic operations), sort_by_key is likely to be faster.

Current implementation

The current algorithm is based on pattern-defeating quicksort by Orson Peters, which combines the fast average case of randomized quicksort with the fast worst case of heapsort, while achieving linear time on slices with certain patterns. It uses some randomization to avoid degenerate cases, but with a fixed seed to always provide deterministic behavior.

In the worst case, the algorithm allocates temporary storage in a Vec<(K, usize)> the length of the slice.

Examples
let mut v = [-5i32, 4, 32, -3, 2];

v.sort_by_cached_key(|k| k.to_string());
assert!(v == [-3, -5, 2, 32, 4]);

Copies self into a new Vec.

Examples
let s = [10, 40, 30];
let x = s.to_vec();
// Here, `s` and `x` can be modified independently.
🔬 This is a nightly-only experimental API. (allocator_api)

Copies self into a new Vec with an allocator.

Examples
#![feature(allocator_api)]

use std::alloc::System;

let s = [10, 40, 30];
let x = s.to_vec_in(System);
// Here, `s` and `x` can be modified independently.

Creates a vector by repeating a slice n times.

Panics

This function will panic if the capacity would overflow.

Examples

Basic usage:

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

A panic upon overflow:

ⓘ
// this will panic at runtime
b"0123456789abcdef".repeat(usize::MAX);

Flattens a slice of T into a single value Self::Output.

Examples
assert_eq!(["hello", "world"].concat(), "helloworld");
assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);

Flattens a slice of T into a single value Self::Output, placing a given separator between each.

Examples
assert_eq!(["hello", "world"].join(" "), "hello world");
assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]);
assert_eq!([[1, 2], [3, 4]].join(&[0, 0][..]), [1, 2, 0, 0, 3, 4]);
👎 Deprecated since 1.3.0:

renamed to join

Flattens a slice of T into a single value Self::Output, placing a given separator between each.

Examples
assert_eq!(["hello", "world"].connect(" "), "hello world");
assert_eq!([[1, 2], [3, 4]].connect(&0), [1, 2, 0, 3, 4]);

Returns a vector containing a copy of this slice where each byte is mapped to its ASCII upper case equivalent.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

Returns a vector containing a copy of this slice where each byte is mapped to its ASCII lower case equivalent.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

Trait Implementations

Generate an arbitrary value of Self from the given unstructured data. Read more

Generate an arbitrary value of Self from the entirety of the given unstructured data. Read more

Get a size hint for how many bytes out of an Unstructured this type needs to construct itself. Read more

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

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

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Returns the “default value” for a type. Read more

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

Executes the destructor for this type. Read more

Append the contents of the iterator to the back of the chunk.

Panics if the chunk exceeds its capacity.

Time: O(n) for the length of the iterator

🔬 This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

🔬 This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements. Read more

Append the contents of the iterator to the back of the chunk.

Panics if the chunk exceeds its capacity.

Time: O(n) for the length of the iterator

🔬 This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

🔬 This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements. Read more

Converts to this type from the input type.

Converts to this type from the input type.

Creates a value from an iterator. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

The returned type after indexing.

Performs the indexing (container[index]) operation. Read more

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

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

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

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Clone an instance of Self into an uninitialised instance of Self. Read more

Initialise an instance of Self to its default state. Read more

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

Like read, except that it reads into a slice of buffers. Read more

🔬 This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation. Read more

Read all bytes until EOF in this source, placing them into buf. Read more

Read all bytes until EOF in this source, appending them to buf. Read more

Read the exact number of bytes required to fill buf. Read more

🔬 This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer. Read more

🔬 This is a nightly-only experimental API. (read_buf)

Read the exact number of bytes required to fill buf. Read more

Creates a “by reference” adaptor for this instance of Read. Read more

Transforms this Read instance to an Iterator over its bytes. Read more

Creates an adapter which will chain this stream with another. Read more

Creates an adapter which will read at most limit bytes from it. Read more

Write a buffer into this writer, returning how many bytes were written. Read more

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

Like write, except that it writes from a slice of buffers. Read more

🔬 This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation. Read more

Attempts to write an entire buffer into this writer. Read more

🔬 This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer. Read more

Writes a formatted string into this writer, returning any error encountered. Read more

Creates a “by reference” adapter for this instance of Write. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.