# Struct rustc_data_structures::snapshot_vec::SnapshotVec

source ·

    pub struct SnapshotVec<D, V = Vec<<D as SnapshotVecDelegate>::Value>, L = VecLog<UndoLog<D>>>where
        D: SnapshotVecDelegate,
        V: VecLike<D>,{
        values: V,
        undo_log: L,
        _marker: PhantomData<D>,
    }

## Fields§

§`values: V`§`undo_log: L`§`_marker: PhantomData<D>`

## Implementations§

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### impl<D, V, L> SnapshotVec<D, V, L>
where D: SnapshotVecDelegate, V: VecLike<D> + Default, L: Default,

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#### pub fn new() -> SnapshotVec<D, V, L>

Creates a new `SnapshotVec`. If `L` is set to `()` then most mutating functions will not be accessible without calling `with_log` and supplying a compatibly `UndoLogs` instance.

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### impl<D> SnapshotVec<D, Vec<<D as SnapshotVecDelegate>::Value>, ()>
where D: SnapshotVecDelegate,

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#### pub fn with_log<'a, L>( &'a mut self, undo_log: L ) -> SnapshotVec<D, &'a mut Vec<<D as SnapshotVecDelegate>::Value>, L>
where L: UndoLogs<UndoLog<D>>,

Creates a `SnapshotVec` using the `undo_log`, allowing mutating methods to be called

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### impl<D, L> SnapshotVec<D, Vec<<D as SnapshotVecDelegate>::Value>, L>
where D: SnapshotVecDelegate, L: Default,

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#### pub fn with_capacity( c: usize ) -> SnapshotVec<D, Vec<<D as SnapshotVecDelegate>::Value>, L>

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### impl<V, D, U> SnapshotVec<D, V, U>
where V: VecLike<D>, D: SnapshotVecDelegate,

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#### pub fn len(&self) -> usize

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#### pub fn get(&self, index: usize) -> &<D as SnapshotVecDelegate>::Value

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#### pub fn get_mut( &mut self, index: usize ) -> &mut <D as SnapshotVecDelegate>::Value

Returns a mutable pointer into the vec; whatever changes you make here cannot be undone automatically, so you should be sure call `record()` with some sort of suitable undo action.

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#### pub fn reserve(&mut self, additional: usize)

Reserve space for new values, just like an ordinary vec.

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### impl<V, D, L> SnapshotVec<D, V, L>
where V: VecLike<D>, D: SnapshotVecDelegate, L: UndoLogs<UndoLog<D>>,

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#### pub fn record(&mut self, action: <D as SnapshotVecDelegate>::Undo)

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#### pub fn push(&mut self, elem: <D as SnapshotVecDelegate>::Value) -> usize

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#### pub fn set(&mut self, index: usize, new_elem: <D as SnapshotVecDelegate>::Value)

Updates the element at the given index. The old value will saved (and perhaps restored) if a snapshot is active.

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#### pub fn set_all( &mut self, new_elems: impl FnMut(usize) -> <D as SnapshotVecDelegate>::Value )

Updates all elements. Potentially more efficient – but otherwise equivalent to – invoking `set` for each element.

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#### pub fn update<OP>(&mut self, index: usize, op: OP)
where OP: FnOnce(&mut <D as SnapshotVecDelegate>::Value), <D as SnapshotVecDelegate>::Value: Clone,

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### impl<D, V, L> SnapshotVec<D, V, L>
where D: SnapshotVecDelegate, V: VecLike<D> + Rollback<UndoLog<D>>, L: Snapshots<UndoLog<D>>,

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#### pub fn start_snapshot( &mut self ) -> Snapshot<<L as Snapshots<UndoLog<D>>>::Snapshot>

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#### pub fn actions_since_snapshot( &self, snapshot: &Snapshot<<L as Snapshots<UndoLog<D>>>::Snapshot> ) -> &[UndoLog<D>]

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#### pub fn rollback_to( &mut self, snapshot: Snapshot<<L as Snapshots<UndoLog<D>>>::Snapshot> )

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#### pub fn commit( &mut self, snapshot: Snapshot<<L as Snapshots<UndoLog<D>>>::Snapshot> )

Commits all changes since the last snapshot. Of course, they can still be undone if there is a snapshot further out.

## Methods from Deref<Target = [<D as SnapshotVecDelegate>::Value]>§

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#### pub fn flatten(&self) -> &[T]

🔬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());

source

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

🔬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]]);

1.79.0 · source

#### pub fn utf8_chunks(&self) -> Utf8Chunks<'_>

Creates an iterator over the contiguous valid UTF-8 ranges of this slice, and the non-UTF-8 fragments in between.

##### §Examples

This function formats arbitrary but mostly-UTF-8 bytes into Rust source code in the form of a C-string literal (`c"..."`).

    use std::fmt::Write as _;

    pub fn cstr_literal(bytes: &[u8]) -> String {
        let mut repr = String::new();
        repr.push_str("c\"");
        for chunk in bytes.utf8_chunks() {
            for ch in chunk.valid().chars() {
                // Escapes \0, \t, \r, \n, \\, \', \", and uses \u{...} for non-printable characters.
                write!(repr, "{}", ch.escape_debug()).unwrap();
            }
            for byte in chunk.invalid() {
                write!(repr, "\\x{:02X}", byte).unwrap();
            }
        }
        repr.push('"');
        repr
    }

    fn main() {
        let lit = cstr_literal(b"\xferris the \xf0\x9f\xa6\x80\x07");
        let expected = stringify!(c"\xFErris the 🦀\u{7}");
        assert_eq!(lit, expected);
    }

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#### pub fn as_str(&self) -> &str

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

Views this slice of ASCII characters as a UTF-8 `str`.

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#### pub fn as_bytes(&self) -> &[u8] ⓘ

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

Views this slice of ASCII characters as a slice of `u8` bytes.

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#### pub fn sort_floats(&mut self)

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

Sorts the slice of floats.

This sort is in-place (i.e. does not allocate), O(n * log(n)) worst-case, and uses the ordering defined by `f32::total_cmp`.

##### §Current implementation

This uses the same sorting algorithm as `sort_unstable_by`.

##### §Examples

    #![feature(sort_floats)]
    let mut v = [2.6, -5e-8, f32::NAN, 8.29, f32::INFINITY, -1.0, 0.0, -f32::INFINITY, -0.0];

    v.sort_floats();
    let sorted = [-f32::INFINITY, -1.0, -5e-8, -0.0, 0.0, 2.6, 8.29, f32::INFINITY, f32::NAN];
    assert_eq!(&v[..8], &sorted[..8]);
    assert!(v[8].is_nan());

1.23.0 · source

#### pub fn is_ascii(&self) -> bool

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

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#### pub fn as_ascii(&self) -> Option<&[AsciiChar]>

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

If this slice `is_ascii`, returns it as a slice of ASCII characters, otherwise returns `None`.

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#### pub unsafe fn as_ascii_unchecked(&self) -> &[AsciiChar]

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

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

##### §Safety

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

1.23.0 · source

#### pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool

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.

1.23.0 · source

#### pub fn make_ascii_uppercase(&mut self)

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`.

1.23.0 · source

#### pub fn make_ascii_lowercase(&mut self)

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`.

1.60.0 · source

#### pub fn escape_ascii(&self) -> EscapeAscii<'_>

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");

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#### pub fn trim_ascii_start(&self) -> &[u8] ⓘ

🔬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"");

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#### pub fn trim_ascii_end(&self) -> &[u8] ⓘ

🔬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"");

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#### pub fn trim_ascii(&self) -> &[u8] ⓘ

🔬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"");

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#### pub fn sort_floats(&mut self)

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

Sorts the slice of floats.

This sort is in-place (i.e. does not allocate), O(n * log(n)) worst-case, and uses the ordering defined by `f64::total_cmp`.

##### §Current implementation

This uses the same sorting algorithm as `sort_unstable_by`.

##### §Examples

    #![feature(sort_floats)]
    let mut v = [2.6, -5e-8, f64::NAN, 8.29, f64::INFINITY, -1.0, 0.0, -f64::INFINITY, -0.0];

    v.sort_floats();
    let sorted = [-f64::INFINITY, -1.0, -5e-8, -0.0, 0.0, 2.6, 8.29, f64::INFINITY, f64::NAN];
    assert_eq!(&v[..8], &sorted[..8]);
    assert!(v[8].is_nan());

1.0.0 · source

#### pub fn len(&self) -> usize

Returns the number of elements in the slice.

##### §Examples

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

1.0.0 · source

#### pub fn is_empty(&self) -> bool

Returns `true` if the slice has a length of 0.

##### §Examples

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

    let b: &[i32] = &[];
    assert!(b.is_empty());

1.0.0 · source

#### pub fn first(&self) -> Option<&T>

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());

1.0.0 · source

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

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]);

    let y: &mut [i32] = &mut [];
    assert_eq!(None, y.first_mut());

1.5.0 · source

#### pub fn split_first(&self) -> Option<(&T, &[T])>

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]);
    }

1.5.0 · source

#### pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])>

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]);

1.5.0 · source

#### pub fn split_last(&self) -> Option<(&T, &[T])>

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]);
    }

1.5.0 · source

#### pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])>

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]);

1.0.0 · source

#### pub fn last(&self) -> Option<&T>

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());

1.0.0 · source

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

Returns a mutable reference to the last item in the slice, or `None` if it is empty.

##### §Examples

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

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

    let y: &mut [i32] = &mut [];
    assert_eq!(None, y.last_mut());

1.77.0 · source

#### pub fn first_chunk<const N: usize>(&self) -> Option<&[T; N]>

Return an array reference to the first `N` items in the slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

    let u = [10, 40, 30];
    assert_eq!(Some(&[10, 40]), u.first_chunk::<2>());

    let v: &[i32] = &[10];
    assert_eq!(None, v.first_chunk::<2>());

    let w: &[i32] = &[];
    assert_eq!(Some(&[]), w.first_chunk::<0>());

1.77.0 · source

#### pub fn first_chunk_mut<const N: usize>(&mut self) -> Option<&mut [T; N]>

Return a mutable array reference to the first `N` items in the slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

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

    if let Some(first) = x.first_chunk_mut::<2>() {
        first[0] = 5;
        first[1] = 4;
    }
    assert_eq!(x, &[5, 4, 2]);

    assert_eq!(None, x.first_chunk_mut::<4>());

1.77.0 · source

#### pub fn split_first_chunk<const N: usize>(&self) -> Option<(&[T; N], &[T])>

Return an array reference to the first `N` items in the slice and the remaining slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

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

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

    assert_eq!(None, x.split_first_chunk::<4>());

1.77.0 · source

#### pub fn split_first_chunk_mut<const N: usize>( &mut self ) -> Option<(&mut [T; N], &mut [T])>

Return a mutable array reference to the first `N` items in the slice and the remaining slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

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

    if let Some((first, elements)) = x.split_first_chunk_mut::<2>() {
        first[0] = 3;
        first[1] = 4;
        elements[0] = 5;
    }
    assert_eq!(x, &[3, 4, 5]);

    assert_eq!(None, x.split_first_chunk_mut::<4>());

1.77.0 · source

#### pub fn split_last_chunk<const N: usize>(&self) -> Option<(&[T], &[T; N])>

Return an array reference to the last `N` items in the slice and the remaining slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

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

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

    assert_eq!(None, x.split_last_chunk::<4>());

1.77.0 · source

#### pub fn split_last_chunk_mut<const N: usize>( &mut self ) -> Option<(&mut [T], &mut [T; N])>

Return a mutable array reference to the last `N` items in the slice and the remaining slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

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

    if let Some((elements, last)) = x.split_last_chunk_mut::<2>() {
        last[0] = 3;
        last[1] = 4;
        elements[0] = 5;
    }
    assert_eq!(x, &[5, 3, 4]);

    assert_eq!(None, x.split_last_chunk_mut::<4>());

1.77.0 · source

#### pub fn last_chunk<const N: usize>(&self) -> Option<&[T; N]>

Return an array reference to the last `N` items in the slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

    let u = [10, 40, 30];
    assert_eq!(Some(&[40, 30]), u.last_chunk::<2>());

    let v: &[i32] = &[10];
    assert_eq!(None, v.last_chunk::<2>());

    let w: &[i32] = &[];
    assert_eq!(Some(&[]), w.last_chunk::<0>());

1.77.0 · source

#### pub fn last_chunk_mut<const N: usize>(&mut self) -> Option<&mut [T; N]>

Return a mutable array reference to the last `N` items in the slice.

If the slice is not at least `N` in length, this will return `None`.

##### §Examples

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

    if let Some(last) = x.last_chunk_mut::<2>() {
        last[0] = 10;
        last[1] = 20;
    }
    assert_eq!(x, &[0, 10, 20]);

    assert_eq!(None, x.last_chunk_mut::<4>());

1.0.0 · source

#### pub fn get<I>(&self, index: I) -> Option<&<I as SliceIndex<[T]>>::Output>
where I: SliceIndex<[T]>,

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));

1.0.0 · source

#### pub fn get_mut<I>( &mut self, index: I ) -> Option<&mut <I as SliceIndex<[T]>>::Output>
where I: SliceIndex<[T]>,

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]);

1.0.0 · source

#### pub unsafe fn get_unchecked<I>( &self, index: I ) -> &<I as SliceIndex<[T]>>::Output
where I: SliceIndex<[T]>,

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.

You can think of this like `.get(index).unwrap_unchecked()`. It’s UB to call `.get_unchecked(len)`, even if you immediately convert to a pointer. And it’s UB to call `.get_unchecked(..len + 1)`, `.get_unchecked(..=len)`, or similar.

##### §Examples

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

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

1.0.0 · source

#### pub unsafe fn get_unchecked_mut<I>( &mut self, index: I ) -> &mut <I as SliceIndex<[T]>>::Output
where I: SliceIndex<[T]>,

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.

You can think of this like `.get_mut(index).unwrap_unchecked()`. It’s UB to call `.get_unchecked_mut(len)`, even if you immediately convert to a pointer. And it’s UB to call `.get_unchecked_mut(..len + 1)`, `.get_unchecked_mut(..=len)`, or similar.

##### §Examples

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

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

1.0.0 · source

#### pub fn as_ptr(&self) -> *const T

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));
        }
    }

1.0.0 · source

#### pub 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 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]);

1.48.0 · source

#### pub fn as_ptr_range(&self) -> Range<*const T>

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));

1.48.0 · source

#### pub fn as_mut_ptr_range(&mut self) -> Range<*mut T>

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++.

1.0.0 · source

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

Swaps two elements in the slice.

If `a` equals to `b`, it’s guaranteed that elements won’t change value.

##### §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"]);

source

#### pub unsafe fn swap_unchecked(&mut self, a: usize, b: usize)

🔬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"]);

1.0.0 · source

#### pub fn reverse(&mut self)

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

##### §Examples

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

1.0.0 · source

#### pub fn iter(&self) -> Iter<'_, T>

Returns an iterator over the slice.

The iterator yields all items from start to end.

##### §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);

1.0.0 · source

#### pub fn iter_mut(&mut self) -> IterMut<'_, T>

Returns an iterator that allows modifying each value.

The iterator yields all items from start to end.

##### §Examples

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

1.0.0 · source

#### pub 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.

##### §Examples

    let slice = ['l', 'o', 'r', 'e', 'm'];
    let mut iter = slice.windows(3);
    assert_eq!(iter.next().unwrap(), &['l', 'o', 'r']);
    assert_eq!(iter.next().unwrap(), &['o', 'r', 'e']);
    assert_eq!(iter.next().unwrap(), &['r', 'e', 'm']);
    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());

There’s no `windows_mut`, as that existing would let safe code violate the “only one `&mut` at a time to the same thing” rule. However, you can sometimes use `Cell::as_slice_of_cells` in conjunction with `windows` to accomplish something similar:

    use std::cell::Cell;

    let mut array = ['R', 'u', 's', 't', ' ', '2', '0', '1', '5'];
    let slice = &mut array[..];
    let slice_of_cells: &[Cell<char>] = Cell::from_mut(slice).as_slice_of_cells();
    for w in slice_of_cells.windows(3) {
        Cell::swap(&w[0], &w[2]);
    }
    assert_eq!(array, ['s', 't', ' ', '2', '0', '1', '5', 'u', 'R']);

1.0.0 · source

#### pub fn chunks(&self, chunk_size: usize) -> Chunks<'_, T>

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());

1.0.0 · source

#### pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T>

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]);

1.31.0 · source

#### pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T>

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']);

1.31.0 · source

#### pub fn chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<'_, T>

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]);

source

#### pub unsafe fn as_chunks_unchecked<const N: usize>(&self) -> &[[T; N]]

🔬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

source

#### pub fn as_chunks<const N: usize>(&self) -> (&[[T; N]], &[T])

🔬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']);

If you expect the slice to be an exact multiple, you can combine `let`-`else` with an empty slice pattern:

    #![feature(slice_as_chunks)]
    let slice = ['R', 'u', 's', 't'];
    let (chunks, []) = slice.as_chunks::<2>() else {
        panic!("slice didn't have even length")
    };
    assert_eq!(chunks, &[['R', 'u'], ['s', 't']]);

source

#### pub fn as_rchunks<const N: usize>(&self) -> (&[T], &[[T; N]])

🔬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']]);

source

#### pub fn array_chunks<const N: usize>(&self) -> ArrayChunks<'_, T, N>

🔬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']);

source

#### pub unsafe fn as_chunks_unchecked_mut<const N: usize>( &mut self ) -> &mut [[T; N]]

🔬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

source

#### pub fn as_chunks_mut<const N: usize>(&mut self) -> (&mut [[T; N]], &mut [T])

🔬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]);

source

#### pub fn as_rchunks_mut<const N: usize>(&mut self) -> (&mut [T], &mut [[T; N]])

🔬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]);

source

#### pub fn array_chunks_mut<const N: usize>(&mut self) -> ArrayChunksMut<'_, T, N>

🔬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]);

source

#### pub fn array_windows<const N: usize>(&self) -> ArrayWindows<'_, T, N>

🔬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());

1.31.0 · source

#### pub fn rchunks(&self, chunk_size: usize) -> RChunks<'_, T>

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());

1.31.0 · source

#### pub fn rchunks_mut(&mut self, chunk_size: usize) -> RChunksMut<'_, T>

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]);

1.31.0 · source

#### pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, T>

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 `rchunks`.

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']);

1.31.0 · source

#### pub fn rchunks_exact_mut(&mut self, chunk_size: usize) -> RChunksExactMut<'_, T>

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]);

1.77.0 · source

#### pub fn chunk_by<F>(&self, pred: F) -> ChunkBy<'_, T, F>
where F: FnMut(&T, &T) -> bool,

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

The predicate is called for every pair of consecutive elements, meaning that it is called on `slice[0]` and `slice[1]`, followed by `slice[1]` and `slice[2]`, and so on.

##### §Examples

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

    let mut iter = slice.chunk_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:

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

    let mut iter = slice.chunk_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);

1.77.0 · source

#### pub fn chunk_by_mut<F>(&mut self, pred: F) -> ChunkByMut<'_, T, F>
where F: FnMut(&T, &T) -> bool,

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

The predicate is called for every pair of consecutive elements, meaning that it is called on `slice[0]` and `slice[1]`, followed by `slice[1]` and `slice[2]`, and so on.

##### §Examples

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

    let mut iter = slice.chunk_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:

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

    let mut iter = slice.chunk_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);

1.0.0 · source

#### pub 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`. For a non-panicking alternative see `split_at_checked`.

##### §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, []);
    }

1.0.0 · source

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

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`. For a non-panicking alternative see `split_at_mut_checked`.

##### §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]);

1.79.0 · source

#### pub unsafe fn split_at_unchecked(&self, mid: usize) -> (&[T], &[T])

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

    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, []);
    }

1.79.0 · source

#### pub unsafe fn split_at_mut_unchecked( &mut self, mid: usize ) -> (&mut [T], &mut [T])

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

    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]);

1.80.0 · source

#### pub fn split_at_checked(&self, mid: usize) -> Option<(&[T], &[T])>

Divides one slice into two at an index, returning `None` if the slice is too short.

If `mid ≤ len` returns a pair of slices where 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).

Otherwise, if `mid > len`, returns `None`.

##### §Examples

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

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

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

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

    assert_eq!(None, v.split_at_checked(7));

1.80.0 · source

#### pub fn split_at_mut_checked( &mut self, mid: usize ) -> Option<(&mut [T], &mut [T])>

Divides one mutable slice into two at an index, returning `None` if the slice is too short.

If `mid ≤ len` returns a pair of slices where 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).

Otherwise, if `mid > len`, returns `None`.

##### §Examples

    let mut v = [1, 0, 3, 0, 5, 6];

    if let Some((left, right)) = v.split_at_mut_checked(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]);

    assert_eq!(None, v.split_at_mut_checked(7));

1.0.0 · source

#### pub 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

    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());

1.0.0 · source

#### pub 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.

##### §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]);

1.51.0 · source

#### pub fn split_inclusive<F>(&self, pred: F) -> SplitInclusive<'_, T, F>
where F: FnMut(&T) -> bool,

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());

1.51.0 · source

#### pub fn split_inclusive_mut<F>(&mut self, pred: F) -> SplitInclusiveMut<'_, T, F>
where F: FnMut(&T) -> bool,

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]);

1.27.0 · source

#### pub fn rsplit<F>(&self, pred: F) -> RSplit<'_, T, F>
where F: FnMut(&T) -> bool,

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);

1.27.0 · source

#### pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<'_, T, F>
where F: FnMut(&T) -> bool,

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]);

1.0.0 · source

#### pub 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]`):

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

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

1.0.0 · source

#### pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<'_, T, F>
where F: FnMut(&T) -> bool,

Returns an iterator over mutable 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]);

1.0.0 · source

#### pub 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]`):

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

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

1.0.0 · source

#### pub 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.

##### §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]);

source

#### pub fn split_once<F>(&self, pred: F) -> Option<(&[T], &[T])>
where F: FnMut(&T) -> bool,

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

Splits the slice on the first element that matches the specified predicate.

If any matching elements are present in the slice, returns the prefix before the match and suffix after. The matching element itself is not included. If no elements match, returns `None`.

##### §Examples

    #![feature(slice_split_once)]
    let s = [1, 2, 3, 2, 4];
    assert_eq!(s.split_once(|&x| x == 2), Some((
        &[1][..],
        &[3, 2, 4][..]
    )));
    assert_eq!(s.split_once(|&x| x == 0), None);

source

#### pub fn rsplit_once<F>(&self, pred: F) -> Option<(&[T], &[T])>
where F: FnMut(&T) -> bool,

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

Splits the slice on the last element that matches the specified predicate.

If any matching elements are present in the slice, returns the prefix before the match and suffix after. The matching element itself is not included. If no elements match, returns `None`.

##### §Examples

    #![feature(slice_split_once)]
    let s = [1, 2, 3, 2, 4];
    assert_eq!(s.rsplit_once(|&x| x == 2), Some((
        &[1, 2, 3][..],
        &[4][..]
    )));
    assert_eq!(s.rsplit_once(|&x| x == 0), None);

1.0.0 · source

#### pub fn contains(&self, x: &T) -> bool
where T: PartialEq,

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"));

1.0.0 · source

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

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

##### §Examples

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

1.0.0 · source

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

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

##### §Examples

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

1.51.0 · source

#### pub fn strip_prefix<P>(&self, prefix: &P) -> Option<&[T]>
where P: SlicePattern<Item = T> + ?Sized, T: PartialEq,

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 `prefix` is equal to the original slice, returns an empty 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(&[10, 40, 30]), Some(&[][..]));
    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()));

1.51.0 · source

#### pub fn strip_suffix<P>(&self, suffix: &P) -> Option<&[T]>
where P: SlicePattern<Item = T> + ?Sized, T: PartialEq,

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 `suffix` is equal to the original slice, returns an empty 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(&[10, 40, 30]), Some(&[][..]));
    assert_eq!(v.strip_suffix(&[50]), None);
    assert_eq!(v.strip_suffix(&[50, 30]), None);

1.0.0 · source

#### pub fn binary_search(&self, x: &T) -> Result<usize, usize>
where T: Ord,

Binary searches this slice for a given element. If the slice is not sorted, the returned result is unspecified and meaningless.

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 find that whole range of matching items, rather than an arbitrary matching one, that can be done using `partition_point`:

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

    let low = s.partition_point(|x| x < &1);
    assert_eq!(low, 1);
    let high = s.partition_point(|x| x <= &1);
    assert_eq!(high, 5);
    let r = s.binary_search(&1);
    assert!((low..high).contains(&r.unwrap()));

    assert!(s[..low].iter().all(|&x| x < 1));
    assert!(s[low..high].iter().all(|&x| x == 1));
    assert!(s[high..].iter().all(|&x| x > 1));

    // For something not found, the "range" of equal items is empty
    assert_eq!(s.partition_point(|x| x < &11), 9);
    assert_eq!(s.partition_point(|x| x <= &11), 9);
    assert_eq!(s.binary_search(&11), Err(9));

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);
    // If `num` is unique, `s.partition_point(|&x| x < num)` (with `<`) is equivalent to
    // `s.binary_search(&num).unwrap_or_else(|x| x)`, but using `<=` will allow `insert`
    // to shift less elements.
    s.insert(idx, num);
    assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);

1.0.0 · source

#### pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>
where F: FnMut(&'a T) -> Ordering,

Binary searches this slice with a comparator function.

The comparator function should return an order code that indicates whether its argument is `Less`, `Equal` or `Greater` the desired target. If the slice is not sorted or if the comparator function does not implement an order consistent with the sort order of the underlying slice, the returned result is unspecified and meaningless.

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, });

1.10.0 · source

#### pub fn binary_search_by_key<'a, B, F>( &'a self, b: &B, f: F ) -> Result<usize, usize>
where F: FnMut(&'a T) -> B, B: Ord,

Binary searches this slice with a key extraction function.

Assumes that the slice is sorted by the key, for instance with `sort_by_key` using the same key extraction function. If the slice is not sorted by the key, the returned result is unspecified and meaningless.

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, });

1.20.0 · source

#### pub fn sort_unstable(&mut self)
where T: Ord,

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]);

1.20.0 · source

#### pub fn sort_unstable_by<F>(&mut self, compare: F)
where F: FnMut(&T, &T) -> Ordering,

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]);

1.20.0 · source

#### pub fn sort_unstable_by_key<K, F>(&mut self, f: F)
where F: FnMut(&T) -> K, K: Ord,

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]);

1.49.0 · source

#### pub fn select_nth_unstable( &mut self, index: usize ) -> (&mut [T], &mut T, &mut [T])
where T: Ord,

Reorder the slice such that the element at `index` after the reordering 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 runs in O(n) time. This function is also known as “kth element” in other libraries.

It returns a triplet of the following from the reordered slice: the subslice prior to `index`, the element at `index`, and the subslice after `index`; accordingly, the values in those two subslices will respectively all be less-than-or-equal-to and greater-than-or-equal-to the value of the element at `index`.

##### §Current implementation

The current algorithm is an introselect implementation based on Pattern Defeating Quicksort, which is also the basis for `sort_unstable`. The fallback algorithm is Median of Medians using Tukey’s Ninther for pivot selection, which guarantees linear runtime for all inputs.

##### §Panics

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

##### §Examples

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

    // Find the items less than or equal to the median, the median, and greater than or equal to
    // the median.
    let (lesser, median, greater) = v.select_nth_unstable(2);

    assert!(lesser == [-3, -5] || lesser == [-5, -3]);
    assert_eq!(median, &mut 1);
    assert!(greater == [4, 2] || greater == [2, 4]);

    // 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]);

1.49.0 · source

#### pub fn select_nth_unstable_by<F>( &mut self, index: usize, compare: F ) -> (&mut [T], &mut T, &mut [T])
where F: FnMut(&T, &T) -> Ordering,

Reorder the slice with a comparator function such that the element at `index` after the reordering 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 runs in O(n) time. This function is also known as “kth element” in other libraries.

It returns a triplet of the following from the slice reordered according to the provided comparator function: the subslice prior to `index`, the element at `index`, and the subslice after `index`; accordingly, the values in those two subslices will respectively all be less-than-or-equal-to and greater-than-or-equal-to the value of the element at `index`.

##### §Current implementation

The current algorithm is an introselect implementation based on Pattern Defeating Quicksort, which is also the basis for `sort_unstable`. The fallback algorithm is Median of Medians using Tukey’s Ninther for pivot selection, which guarantees linear runtime for all inputs.

##### §Panics

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

##### §Examples

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

    // Find the items less than or equal to the median, the median, and greater than or equal to
    // the median as if the slice were sorted in descending order.
    let (lesser, median, greater) = v.select_nth_unstable_by(2, |a, b| b.cmp(a));

    assert!(lesser == [4, 2] || lesser == [2, 4]);
    assert_eq!(median, &mut 1);
    assert!(greater == [-3, -5] || greater == [-5, -3]);

    // 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]);

1.49.0 · source

#### pub fn select_nth_unstable_by_key<K, F>( &mut self, index: usize, f: F ) -> (&mut [T], &mut T, &mut [T])
where F: FnMut(&T) -> K, K: Ord,

Reorder the slice with a key extraction function such that the element at `index` after the reordering 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 runs in O(n) time. This function is also known as “kth element” in other libraries.

It returns a triplet of the following from the slice reordered according to the provided key extraction function: the subslice prior to `index`, the element at `index`, and the subslice after `index`; accordingly, the values in those two subslices will respectively all be less-than-or-equal-to and greater-than-or-equal-to the value of the element at `index`.

##### §Current implementation

The current algorithm is an introselect implementation based on Pattern Defeating Quicksort, which is also the basis for `sort_unstable`. The fallback algorithm is Median of Medians using Tukey’s Ninther for pivot selection, which guarantees linear runtime for all inputs.

##### §Panics

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

##### §Examples

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

    // Find the items less than or equal to the median, the median, and greater than or equal to
    // the median as if the slice were sorted according to absolute value.
    let (lesser, median, greater) = v.select_nth_unstable_by_key(2, |a| a.abs());

    assert!(lesser == [1, 2] || lesser == [2, 1]);
    assert_eq!(median, &mut -3);
    assert!(greater == [4, -5] || greater == [-5, 4]);

    // 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]);

source

#### pub fn partition_dedup(&mut self) -> (&mut [T], &mut [T])
where T: PartialEq,

🔬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]);

source

#### pub fn partition_dedup_by<F>(&mut self, same_bucket: F) -> (&mut [T], &mut [T])
where F: FnMut(&mut T, &mut T) -> bool,

🔬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"]);

source

#### pub fn partition_dedup_by_key<K, F>(&mut self, key: F) -> (&mut [T], &mut [T])
where F: FnMut(&mut T) -> K, K: PartialEq,

🔬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]);

1.26.0 · source

#### pub fn rotate_left(&mut self, mid: usize)

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']);

1.26.0 · source

#### pub fn rotate_right(&mut self, k: usize)

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']);

Rotating 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']);

1.50.0 · source

#### pub fn fill(&mut self, value: T)
where T: Clone,

Fills `self` with elements by cloning `value`.

##### §Examples

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

1.51.0 · source

#### pub fn fill_with<F>(&mut self, f: F)
where F: FnMut() -> T,

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]);

1.7.0 · source

#### pub fn clone_from_slice(&mut self, src: &[T])
where T: Clone,

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]);

1.9.0 · source

#### pub 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`.

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]);

1.37.0 · source

#### pub fn copy_within<R>(&mut self, src: R, dest: usize)
where R: RangeBounds<usize>, T: Copy,

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!");

1.27.0 · source

#### pub fn swap_with_slice(&mut self, other: &mut [T])

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]);

1.30.0 · source

#### pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T])

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 middle part will be as big as possible under the given alignment constraint and element size.

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);
    }

1.30.0 · source

#### pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T])

Transmute the mutable slice to a mutable 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 middle part will be as big as possible under the given alignment constraint and element size.

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);
    }

source

#### pub fn as_simd<const LANES: usize>(&self) -> (&[T], &[Simd<T, LANES>], &[T])
where Simd<T, LANES>: AsRef<[T; LANES]>, T: SimdElement, LaneCount<LANES>: SupportedLaneCount,

🔬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)]
    use core::simd::prelude::*;

    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;
        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);

source

#### pub fn as_simd_mut<const LANES: usize>( &mut self ) -> (&mut [T], &mut [Simd<T, LANES>], &mut [T])
where Simd<T, LANES>: AsMut<[T; LANES]>, T: SimdElement, LaneCount<LANES>: SupportedLaneCount,

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

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

source

#### pub fn is_sorted(&self) -> bool
where T: PartialOrd,

🔬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());

source

#### pub fn is_sorted_by<'a, F>(&'a self, compare: F) -> bool
where F: FnMut(&'a T, &'a T) -> bool,

🔬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 whether two elements are to be considered in sorted order.

##### §Examples

    #![feature(is_sorted)]

    assert!([1, 2, 2, 9].is_sorted_by(|a, b| a <= b));
    assert!(![1, 2, 2, 9].is_sorted_by(|a, b| a < b));

    assert!([0].is_sorted_by(|a, b| true));
    assert!([0].is_sorted_by(|a, b| false));

    let empty: [i32; 0] = [];
    assert!(empty.is_sorted_by(|a, b| false));
    assert!(empty.is_sorted_by(|a, b| true));

source

#### pub fn is_sorted_by_key<'a, F, K>(&'a self, f: F) -> bool
where F: FnMut(&'a T) -> K, K: PartialOrd,

🔬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()));

1.52.0 · source

#### pub fn partition_point<P>(&self, pred: P) -> usize
where P: FnMut(&T) -> bool,

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 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 all elements of the slice match the predicate, including if the slice is empty, then the length of the slice will be returned:

    let a = [2, 4, 8];
    assert_eq!(a.partition_point(|x| x < &100), a.len());
    let a: [i32; 0] = [];
    assert_eq!(a.partition_point(|x| x < &100), 0);

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]);

source

#### pub fn take<'a, R>(self: &mut &'a [T], range: R) -> Option<&'a [T]>
where R: OneSidedRange<usize>,

🔬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));

source

#### pub fn take_mut<'a, R>(self: &mut &'a mut [T], range: R) -> Option<&'a mut [T]>
where R: OneSidedRange<usize>,

🔬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));

source

#### pub fn take_first<'a>(self: &mut &'a [T]) -> Option<&'a T>

🔬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');

source

#### pub fn take_first_mut<'a>(self: &mut &'a mut [T]) -> Option<&'a mut T>

🔬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');

source

#### pub fn take_last<'a>(self: &mut &'a [T]) -> Option<&'a T>

🔬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');

source

#### pub fn take_last_mut<'a>(self: &mut &'a mut [T]) -> Option<&'a mut T>

🔬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');

source

#### pub unsafe fn get_many_unchecked_mut<const N: usize>( &mut self, indices: [usize; N] ) -> [&mut T; N]

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

Returns mutable references to many indices at once, without doing any checks.

For a safe alternative see `get_many_mut`.

##### §Safety

Calling this method with overlapping or out-of-bounds indices is undefined behavior even if the resulting references are not used.

##### §Examples

    #![feature(get_many_mut)]

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

    unsafe {
        let [a, b] = x.get_many_unchecked_mut([0, 2]);
        *a *= 10;
        *b *= 100;
    }
    assert_eq!(x, &[10, 2, 400]);

source

#### pub fn get_many_mut<const N: usize>( &mut self, indices: [usize; N] ) -> Result<[&mut T; N], GetManyMutError<N>>

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

Returns mutable references to many indices at once.

Returns an error if any index is out-of-bounds, or if the same index was passed more than once.

##### §Examples

    #![feature(get_many_mut)]

    let v = &mut [1, 2, 3];
    if let Ok([a, b]) = v.get_many_mut([0, 2]) {
        *a = 413;
        *b = 612;
    }
    assert_eq!(v, &[413, 2, 612]);

1.0.0 · source

#### pub fn sort(&mut self)
where T: Ord,

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]);

1.0.0 · source

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

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]);

1.7.0 · source

#### pub fn sort_by_key<K, F>(&mut self, f: F)
where F: FnMut(&T) -> K, K: Ord,

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]);

1.34.0 · source

#### pub fn sort_by_cached_key<K, F>(&mut self, f: F)
where F: FnMut(&T) -> K, K: Ord,

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]);

1.0.0 · source

#### pub fn to_vec(&self) -> Vec<T>
where T: Clone,

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.

source

#### pub fn to_vec_in<A>(&self, alloc: A) -> Vec<T, A>
where A: Allocator, T: Clone,

🔬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.

1.40.0 · source

#### pub fn repeat(&self, n: usize) -> Vec<T>
where T: Copy,

Creates a vector by copying 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);

1.0.0 · source

#### pub fn concat<Item>(&self) -> <[T] as Concat<Item>>::Output ⓘ
where [T]: Concat<Item>, Item: ?Sized,

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]);

1.3.0 · source

#### pub fn join<Separator>( &self, sep: Separator ) -> <[T] as Join<Separator>>::Output ⓘ
where [T]: Join<Separator>,

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]);

1.0.0 · source

#### pub fn connect<Separator>( &self, sep: Separator ) -> <[T] as Join<Separator>>::Output ⓘ
where [T]: Join<Separator>,

👎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]);

1.23.0 · source

#### pub fn to_ascii_uppercase(&self) -> Vec<u8> ⓘ

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`.

1.23.0 · source

#### pub fn to_ascii_lowercase(&self) -> Vec<u8> ⓘ

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§

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### impl<D, V, L> Clone for SnapshotVec<D, V, L>
where D: SnapshotVecDelegate, V: VecLike<D> + Clone, L: Clone,

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### impl<D, V, L> Debug for SnapshotVec<D, V, L>
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### impl<D, V, L> DerefMut for SnapshotVec<D, V, L>
where D: SnapshotVecDelegate, V: VecLike<D>,

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Mutably dereferences the value.
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#### fn extend<T>(&mut self, iterable: T)
where T: IntoIterator<Item = <D as SnapshotVecDelegate>::Value>,

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#### fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (`extend_one`)
Extends a collection with exactly one element.
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🔬This is a nightly-only experimental API. (`extend_one`)
Reserves capacity in a collection for the given number of additional elements. Read more
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### impl<D, V, L> Index<usize> for SnapshotVec<D, V, L>
where D: SnapshotVecDelegate, V: VecLike<D>,

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Performs the indexing (`container[index]`) operation. Read more
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#### fn index_mut(&mut self, index: usize) -> &mut <D as SnapshotVecDelegate>::Value

Performs the mutable indexing (`container[index]`) operation. Read more
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### impl<D> Rollback<UndoLog<D>> for SnapshotVec<D, Vec<<D as SnapshotVecDelegate>::Value>, ()>
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#### fn reverse(&mut self, undo: UndoLog<D>)

## Auto Trait Implementations§

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### impl<D, V, L> DynSend for SnapshotVec<D, V, L>
where V: DynSend, L: DynSend, D: DynSend,

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### impl<D, V, L> DynSync for SnapshotVec<D, V, L>
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### impl<D, V, L> Freeze for SnapshotVec<D, V, L>
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### impl<D, V, L> RefUnwindSafe for SnapshotVec<D, V, L>
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#### const ALIGN: Alignment = const ALIGN: Alignment = Alignment::of::<Self>();

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Immutably borrows from an owned value. Read more
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Mutably borrows from an owned value. Read more
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Returns the argument unchanged.

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Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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Calls `U::from(self)`.

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Dereferences the given pointer. Read more
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