SnapshotVec in rustc_data_structures::snapshot_vec - Rust (original) (raw)
Struct SnapshotVec
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>,
}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.
Creates a SnapshotVec using the undo_log, allowing mutating methods to be called
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.
Reserve space for new values, just like an ordinary vec.
Updates the element at the given index. The old value will saved (and perhaps restored) if a snapshot is active.
Updates all elements. Potentially more efficient – but otherwise equivalent to – invoking set for each element.
Commits all changes since the last snapshot. Of course, they can still be undone if there is a snapshot further out.
1.0.0 · Source
Returns the number of elements in the slice.
§Examples
let a = [1, 2, 3];
assert_eq!(a.len(), 3);1.0.0 · Source
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
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
Returns a mutable reference 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
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
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
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
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
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
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
Returns 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
Returns 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
Returns 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
Returns 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
Returns 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
Returns 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
Returns 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
Returns 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
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
Noneif out of bounds. - If given a range, returns the subslice corresponding to that range, or
Noneif 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
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
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
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
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 dangling.
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
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 dangling.
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
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
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++.
1.94.0 · Source
Gets a reference to the underlying array.
If N is not exactly equal to the length of self, then this method returns None.
1.94.0 · Source
Gets a mutable reference to the slice’s underlying array.
If N is not exactly equal to the length of self, then this method returns None.
1.0.0 · Source
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"]);🔬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
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
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
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
Returns an iterator over all contiguous windows of lengthsize. The windows overlap. If the slice is shorter thansize, the iterator returns no values.
§Panics
Panics if size is zero.
§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());Because the Iterator trait cannot represent the required lifetimes, there is no windows_mut analog to windows;[0,1,2].windows_mut(2).collect() would violate the rules of references(though a LendingIterator analog is possible). You can sometimes useCell::as_slice_of_cells in conjunction with windows instead:
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
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 exactlychunk_size elements, and rchunks for the same iterator but starting at the end of the slice.
If your chunk_size is a constant, consider using as_chunks instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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.
If your chunk_size is a constant, consider using as_chunks_mut instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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.
If your chunk_size is a constant, consider using as_chunks instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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.
If your chunk_size is a constant, consider using as_chunks_mut instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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]);1.88.0 · Source
Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.
This is the inverse operation to as_flattened.
As this is unsafe, consider whether you could use as_chunks oras_rchunks instead, perhaps via something likeif let (chunks, []) = slice.as_chunks() orlet (chunks, []) = slice.as_chunks() else { unreachable!() };.
§Safety
This may only be called when
- The slice splits exactly into
N-element chunks (akaself.len() % N == 0). N != 0.
§Examples
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 allowed1.88.0 · Source
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.
The remainder is meaningful in the division sense. Givenlet (chunks, remainder) = slice.as_chunks(), then:
chunks.len()equalsslice.len() / N,remainder.len()equalsslice.len() % N, andslice.len()equalschunks.len() * N + remainder.len().
You can flatten the chunks back into a slice-of-T with as_flattened.
§Panics
Panics if N is zero.
Note that this check is against a const generic parameter, not a runtime value, and thus a particular monomorphization will either always panic or it will never panic.
§Examples
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 combinelet-else with an empty slice pattern:
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']]);1.88.0 · Source
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.
The remainder is meaningful in the division sense. Givenlet (remainder, chunks) = slice.as_rchunks(), then:
remainder.len()equalsslice.len() % N,chunks.len()equalsslice.len() / N, andslice.len()equalschunks.len() * N + remainder.len().
You can flatten the chunks back into a slice-of-T with as_flattened.
§Panics
Panics if N is zero.
Note that this check is against a const generic parameter, not a runtime value, and thus a particular monomorphization will either always panic or it will never panic.
§Examples
let slice = ['l', 'o', 'r', 'e', 'm'];
let (remainder, chunks) = slice.as_rchunks();
assert_eq!(remainder, &['l']);
assert_eq!(chunks, &[['o', 'r'], ['e', 'm']]);1.88.0 · Source
Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.
This is the inverse operation to as_flattened_mut.
As this is unsafe, consider whether you could use as_chunks_mut oras_rchunks_mut instead, perhaps via something likeif let (chunks, []) = slice.as_chunks_mut() orlet (chunks, []) = slice.as_chunks_mut() else { unreachable!() };.
§Safety
This may only be called when
- The slice splits exactly into
N-element chunks (akaself.len() % N == 0). N != 0.
§Examples
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 allowed1.88.0 · Source
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.
The remainder is meaningful in the division sense. Givenlet (chunks, remainder) = slice.as_chunks_mut(), then:
chunks.len()equalsslice.len() / N,remainder.len()equalsslice.len() % N, andslice.len()equalschunks.len() * N + remainder.len().
You can flatten the chunks back into a slice-of-T with as_flattened_mut.
§Panics
Panics if N is zero.
Note that this check is against a const generic parameter, not a runtime value, and thus a particular monomorphization will either always panic or it will never panic.
§Examples
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]);1.88.0 · Source
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.
The remainder is meaningful in the division sense. Givenlet (remainder, chunks) = slice.as_rchunks_mut(), then:
remainder.len()equalsslice.len() % N,chunks.len()equalsslice.len() / N, andslice.len()equalschunks.len() * N + remainder.len().
You can flatten the chunks back into a slice-of-T with as_flattened_mut.
§Panics
Panics if N is zero.
Note that this check is against a const generic parameter, not a runtime value, and thus a particular monomorphization will either always panic or it will never panic.
§Examples
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]);1.94.0 · Source
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 zero.
Note that this check is against a const generic parameter, not a runtime value, and thus a particular monomorphization will either always panic or it will never panic.
§Examples
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
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 exactlychunk_size elements, and chunks for the same iterator but starting at the beginning of the slice.
If your chunk_size is a constant, consider using as_rchunks instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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.
If your chunk_size is a constant, consider using as_rchunks_mut instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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.
If your chunk_size is a constant, consider using as_rchunks instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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.
If your chunk_size is a constant, consider using as_rchunks_mut instead, which will give references to arrays of exactly that length, rather than slices.
§Panics
Panics if chunk_size is zero.
§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
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
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
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 seesplit_at_checked.
§Examples
let v = ['a', 'b', 'c'];
{
let (left, right) = v.split_at(0);
assert_eq!(left, []);
assert_eq!(right, ['a', 'b', 'c']);
}
{
let (left, right) = v.split_at(2);
assert_eq!(left, ['a', 'b']);
assert_eq!(right, ['c']);
}
{
let (left, right) = v.split_at(3);
assert_eq!(left, ['a', 'b', 'c']);
assert_eq!(right, []);
}1.0.0 · Source
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 seesplit_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
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 that0 <= mid <= self.len().
§Examples
let v = ['a', 'b', 'c'];
unsafe {
let (left, right) = v.split_at_unchecked(0);
assert_eq!(left, []);
assert_eq!(right, ['a', 'b', 'c']);
}
unsafe {
let (left, right) = v.split_at_unchecked(2);
assert_eq!(left, ['a', 'b']);
assert_eq!(right, ['c']);
}
unsafe {
let (left, right) = v.split_at_unchecked(3);
assert_eq!(left, ['a', 'b', 'c']);
assert_eq!(right, []);
}1.79.0 · Source
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 that0 <= 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
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 indexlen 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
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 indexlen 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
Returns an iterator over subslices separated by elements that matchpred. 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
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
Returns an iterator over subslices separated by elements that matchpred. 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
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
Returns an iterator over subslices separated by elements that matchpred, 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
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
Returns an iterator over subslices separated by elements that matchpred, 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
Returns an iterator over mutable subslices separated by elements that matchpred, 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
Returns an iterator over subslices separated by elements that matchpred 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
Returns an iterator over subslices separated by elements that matchpred 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]);🔬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);🔬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
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
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
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
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
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);🔬This is a nightly-only experimental API. (strip_circumfix)
Returns a subslice with the prefix and suffix removed.
If the slice starts with prefix and ends with suffix, returns the subslice after the prefix and before the suffix, wrapped in Some.
If the slice does not start with prefix or does not end with suffix, returns None.
§Examples
#![feature(strip_circumfix)]
let v = &[10, 50, 40, 30];
assert_eq!(v.strip_circumfix(&[10], &[30]), Some(&[50, 40][..]));
assert_eq!(v.strip_circumfix(&[10], &[40, 30]), Some(&[50][..]));
assert_eq!(v.strip_circumfix(&[10, 50], &[40, 30]), Some(&[][..]));
assert_eq!(v.strip_circumfix(&[50], &[30]), None);
assert_eq!(v.strip_circumfix(&[10], &[40]), None);
assert_eq!(v.strip_circumfix(&[], &[40, 30]), Some(&[10, 50][..]));
assert_eq!(v.strip_circumfix(&[10, 50], &[]), Some(&[40, 30][..]));🔬This is a nightly-only experimental API. (trim_prefix_suffix)
Returns a subslice with the optional prefix removed.
If the slice starts with prefix, returns the subslice after the prefix. If prefixis empty or the slice does not start with prefix, simply returns the original slice. If prefix is equal to the original slice, returns an empty slice.
§Examples
#![feature(trim_prefix_suffix)]
let v = &[10, 40, 30];
// Prefix present - removes it
assert_eq!(v.trim_prefix(&[10]), &[40, 30][..]);
assert_eq!(v.trim_prefix(&[10, 40]), &[30][..]);
assert_eq!(v.trim_prefix(&[10, 40, 30]), &[][..]);
// Prefix absent - returns original slice
assert_eq!(v.trim_prefix(&[50]), &[10, 40, 30][..]);
assert_eq!(v.trim_prefix(&[10, 50]), &[10, 40, 30][..]);
let prefix : &str = "he";
assert_eq!(b"hello".trim_prefix(prefix.as_bytes()), b"llo".as_ref());🔬This is a nightly-only experimental API. (trim_prefix_suffix)
Returns a subslice with the optional suffix removed.
If the slice ends with suffix, returns the subslice before the suffix. If suffixis empty or the slice does not end with suffix, simply returns the original slice. If suffix is equal to the original slice, returns an empty slice.
§Examples
#![feature(trim_prefix_suffix)]
let v = &[10, 40, 30];
// Suffix present - removes it
assert_eq!(v.trim_suffix(&[30]), &[10, 40][..]);
assert_eq!(v.trim_suffix(&[40, 30]), &[10][..]);
assert_eq!(v.trim_suffix(&[10, 40, 30]), &[][..]);
// Suffix absent - returns original slice
assert_eq!(v.trim_suffix(&[50]), &[10, 40, 30][..]);
assert_eq!(v.trim_suffix(&[50, 30]), &[10, 40, 30][..]);1.0.0 · Source
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
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
Binary searches this slice with a key extraction function.
Assumes that the slice is sorted by the key, for instance withsort_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
Sorts the slice in ascending order without preserving the initial 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.
If the implementation of Ord for T does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
For example |a, b| (a - b).cmp(a) is a comparison function that is neither transitive nor reflexive nor total, a < b < c < a with a = 1, b = 2, c = 3. For more information and examples see the Ord documentation.
All original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. Same is true if the implementation of Ord for T panics.
Sorting types that only implement PartialOrd such as f32 and f64 require additional precautions. For example, f32::NAN != f32::NAN, which doesn’t fulfill the reflexivity requirement of Ord. By using an alternative comparison function withslice::sort_unstable_by such as f32::total_cmp or f64::total_cmp that defines atotal order users can sort slices containing floating-point values. Alternatively, if all values in the slice are guaranteed to be in a subset for which PartialOrd::partial_cmpforms a total order, it’s possible to sort the slice with sort_unstable_by(|a, b| a.partial_cmp(b).unwrap()).
§Current implementation
The current implementation is based on ipnsort by Lukas Bergdoll and Orson Peters, which combines the fast average case of quicksort with the fast worst case of heapsort, achieving linear time on fully sorted and reversed inputs. On inputs with k distinct elements, the expected time to sort the data is O(n * log(k)).
It is typically faster than stable sorting, except in a few special cases, e.g., when the slice is partially sorted.
§Panics
May panic if the implementation of Ord for T does not implement a total order, or if the Ord implementation panics.
§Examples
let mut v = [4, -5, 1, -3, 2];
v.sort_unstable();
assert_eq!(v, [-5, -3, 1, 2, 4]);1.20.0 · Source
Sorts the slice in ascending order with a comparison function, without preserving the initial 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.
If the comparison function compare does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
For example |a, b| (a - b).cmp(a) is a comparison function that is neither transitive nor reflexive nor total, a < b < c < a with a = 1, b = 2, c = 3. For more information and examples see the Ord documentation.
All original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. Same is true if compare panics.
§Current implementation
The current implementation is based on ipnsort by Lukas Bergdoll and Orson Peters, which combines the fast average case of quicksort with the fast worst case of heapsort, achieving linear time on fully sorted and reversed inputs. On inputs with k distinct elements, the expected time to sort the data is O(n * log(k)).
It is typically faster than stable sorting, except in a few special cases, e.g., when the slice is partially sorted.
§Panics
May panic if the compare does not implement a total order, or if the compare itself panics.
§Examples
let mut v = [4, -5, 1, -3, 2];
v.sort_unstable_by(|a, b| a.cmp(b));
assert_eq!(v, [-5, -3, 1, 2, 4]);
// reverse sorting
v.sort_unstable_by(|a, b| b.cmp(a));
assert_eq!(v, [4, 2, 1, -3, -5]);1.20.0 · Source
Sorts the slice in ascending order with a key extraction function, without preserving the initial 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.
If the implementation of Ord for K does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
For example |a, b| (a - b).cmp(a) is a comparison function that is neither transitive nor reflexive nor total, a < b < c < a with a = 1, b = 2, c = 3. For more information and examples see the Ord documentation.
All original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. Same is true if the implementation of Ord for K panics.
§Current implementation
The current implementation is based on ipnsort by Lukas Bergdoll and Orson Peters, which combines the fast average case of quicksort with the fast worst case of heapsort, achieving linear time on fully sorted and reversed inputs. On inputs with k distinct elements, the expected time to sort the data is O(n * log(k)).
It is typically faster than stable sorting, except in a few special cases, e.g., when the slice is partially sorted.
§Panics
May panic if the implementation of Ord for K does not implement a total order, or if the Ord implementation panics.
§Examples
let mut v = [4i32, -5, 1, -3, 2];
v.sort_unstable_by_key(|k| k.abs());
assert_eq!(v, [1, 2, -3, 4, -5]);1.49.0 · Source
Reorders the slice such that the element at index is at a sort-order position. All elements before index will be <= to this value, and all elements after will be >= to it.
This reordering is unstable (i.e. any element that compares equal to the nth element may end up at that position), in-place (i.e. does not allocate), and runs in O(n) time. This function is also known as “kth element” in other libraries.
Returns a triple that partitions the reordered slice:
- The unsorted subslice before
index, whose elements all satisfyx <= self[index]. - The element at
index. - The unsorted subslice after
index, whose elements all satisfyx >= self[index].
§Current implementation
The current algorithm is an introselect implementation based on ipnsort by Lukas Bergdoll and Orson Peters, 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(), and so always panics on empty slices.
May panic if the implementation of Ord for T does not implement a total order.
§Examples
let mut v = [-5i32, 4, 2, -3, 1];
// Find the items `<=` to the median, the median itself, and the items `>=` to it.
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
Reorders the slice with a comparator function such that the element at index is at a sort-order position. All elements before index will be <= to this value, and all elements after will be >= to it, according to the comparator function.
This reordering is unstable (i.e. any element that compares equal to the nth element may end up at that position), in-place (i.e. does not allocate), and runs in O(n) time. This function is also known as “kth element” in other libraries.
Returns a triple partitioning the reordered slice:
- The unsorted subslice before
index, whose elements all satisfycompare(x, self[index]).is_le(). - The element at
index. - The unsorted subslice after
index, whose elements all satisfycompare(x, self[index]).is_ge().
§Current implementation
The current algorithm is an introselect implementation based on ipnsort by Lukas Bergdoll and Orson Peters, 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(), and so always panics on empty slices.
May panic if compare does not implement a total order.
§Examples
let mut v = [-5i32, 4, 2, -3, 1];
// Find the items `>=` to the median, the median itself, and the items `<=` to it, by using
// a reversed comparator.
let (before, median, after) = v.select_nth_unstable_by(2, |a, b| b.cmp(a));
assert!(before == [4, 2] || before == [2, 4]);
assert_eq!(median, &mut 1);
assert!(after == [-3, -5] || after == [-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
Reorders the slice with a key extraction function such that the element at index is at a sort-order position. All elements before index will have keys <= to the key at index, and all elements after will have keys >= to it.
This reordering is unstable (i.e. any element that compares equal to the nth element may end up at that position), in-place (i.e. does not allocate), and runs in O(n) time. This function is also known as “kth element” in other libraries.
Returns a triple partitioning the reordered slice:
- The unsorted subslice before
index, whose elements all satisfyf(x) <= f(self[index]). - The element at
index. - The unsorted subslice after
index, whose elements all satisfyf(x) >= f(self[index]).
§Current implementation
The current algorithm is an introselect implementation based on ipnsort by Lukas Bergdoll and Orson Peters, 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.
May panic if K: Ord does not implement a total order.
§Examples
let mut v = [-5i32, 4, 1, -3, 2];
// Find the items `<=` to the absolute median, the absolute median itself, and the items
// `>=` to it.
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]);🔬This is a nightly-only experimental API. (slice_partition_dedup)
Moves all consecutive repeated elements to the end of the slice according to thePartialEq trait implementation.
Returns two slices. The first contains no consecutive repeated elements. The second contains all the duplicates in no specified order.
If the slice is sorted, the first returned slice contains no duplicates.
§Examples
#![feature(slice_partition_dedup)]
let mut slice = [1, 2, 2, 3, 3, 2, 1, 1];
let (dedup, duplicates) = slice.partition_dedup();
assert_eq!(dedup, [1, 2, 3, 2, 1]);
assert_eq!(duplicates, [2, 3, 1]);🔬This is a nightly-only experimental API. (slice_partition_dedup)
Moves all but the first of consecutive elements to the end of the slice satisfying a given equality relation.
Returns two slices. The first contains no consecutive repeated elements. The second contains all the duplicates in no specified order.
The same_bucket function is passed references to two elements from the slice and must determine if the elements compare equal. The elements are passed in opposite order from their order in the slice, so if same_bucket(a, b) returns true, a is moved at the end of the slice.
If the slice is sorted, the first returned slice contains no duplicates.
§Examples
#![feature(slice_partition_dedup)]
let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"];
let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b));
assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]);
assert_eq!(duplicates, ["bar", "Foo", "BAZ"]);🔬This is a nightly-only experimental API. (slice_partition_dedup)
Moves all but the first of consecutive elements to the end of the slice that resolve to the same key.
Returns two slices. The first contains no consecutive repeated elements. The second contains all the duplicates in no specified order.
If the slice is sorted, the first returned slice contains no duplicates.
§Examples
#![feature(slice_partition_dedup)]
let mut slice = [10, 20, 21, 30, 30, 20, 11, 13];
let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10);
assert_eq!(dedup, [10, 20, 30, 20, 11]);
assert_eq!(duplicates, [21, 30, 13]);1.26.0 · Source
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
Rotates the slice in-place such that the first self.len() - kelements of the slice move to the end while the last k elements move to the front.
After calling rotate_right, the element previously at indexself.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
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
Fills self with elements returned by calling a closure repeatedly.
This method uses a closure to create new values. If you’d ratherClone a given value, use fill. If you want to use the Defaulttrait 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
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
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
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
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
Transmutes 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
Transmutes 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);
}🔬This is a nightly-only experimental API. (portable_simd)
Splits a slice into a prefix, a middle of aligned SIMD types, and a suffix.
This is a safe wrapper around slice::align_to, so inherits the same guarantees as that method.
§Panics
This will panic if the size of the SIMD type is different fromLANES 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);🔬This is a nightly-only experimental API. (portable_simd)
Splits 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 inherits the same guarantees as that method.
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 fromLANES 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.
1.82.0 · Source
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
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());1.82.0 · Source
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 comparefunction to determine whether two elements are to be considered in sorted order.
§Examples
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));1.82.0 · Source
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
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
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]);1.87.0 · Source
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 as2.. or ..6, but not 2..6.
§Examples
Splitting off the first three elements of a slice:
let mut slice: &[_] = &['a', 'b', 'c', 'd'];
let mut first_three = slice.split_off(..3).unwrap();
assert_eq!(slice, &['d']);
assert_eq!(first_three, &['a', 'b', 'c']);Splitting off a slice starting with the third element:
let mut slice: &[_] = &['a', 'b', 'c', 'd'];
let mut tail = slice.split_off(2..).unwrap();
assert_eq!(slice, &['a', 'b']);
assert_eq!(tail, &['c', 'd']);Getting None when range is out of bounds:
let mut slice: &[_] = &['a', 'b', 'c', 'd'];
assert_eq!(None, slice.split_off(5..));
assert_eq!(None, slice.split_off(..5));
assert_eq!(None, slice.split_off(..=4));
let expected: &[char] = &['a', 'b', 'c', 'd'];
assert_eq!(Some(expected), slice.split_off(..4));1.87.0 · Source
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 as2.. or ..6, but not 2..6.
§Examples
Splitting off the first three elements of a slice:
let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
let mut first_three = slice.split_off_mut(..3).unwrap();
assert_eq!(slice, &mut ['d']);
assert_eq!(first_three, &mut ['a', 'b', 'c']);Splitting off a slice starting with the third element:
let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
let mut tail = slice.split_off_mut(2..).unwrap();
assert_eq!(slice, &mut ['a', 'b']);
assert_eq!(tail, &mut ['c', 'd']);Getting None when range is out of bounds:
let mut slice: &mut [_] = &mut ['a', 'b', 'c', 'd'];
assert_eq!(None, slice.split_off_mut(5..));
assert_eq!(None, slice.split_off_mut(..5));
assert_eq!(None, slice.split_off_mut(..=4));
let expected: &mut [_] = &mut ['a', 'b', 'c', 'd'];
assert_eq!(Some(expected), slice.split_off_mut(..4));1.87.0 · Source
Removes the first element of the slice and returns a reference to it.
Returns None if the slice is empty.
§Examples
let mut slice: &[_] = &['a', 'b', 'c'];
let first = slice.split_off_first().unwrap();
assert_eq!(slice, &['b', 'c']);
assert_eq!(first, &'a');1.87.0 · Source
Removes the first element of the slice and returns a mutable reference to it.
Returns None if the slice is empty.
§Examples
let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
let first = slice.split_off_first_mut().unwrap();
*first = 'd';
assert_eq!(slice, &['b', 'c']);
assert_eq!(first, &'d');1.87.0 · Source
Removes the last element of the slice and returns a reference to it.
Returns None if the slice is empty.
§Examples
let mut slice: &[_] = &['a', 'b', 'c'];
let last = slice.split_off_last().unwrap();
assert_eq!(slice, &['a', 'b']);
assert_eq!(last, &'c');1.87.0 · Source
Removes the last element of the slice and returns a mutable reference to it.
Returns None if the slice is empty.
§Examples
let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
let last = slice.split_off_last_mut().unwrap();
*last = 'd';
assert_eq!(slice, &['a', 'b']);
assert_eq!(last, &'d');1.86.0 · Source
Returns mutable references to many indices at once, without doing any checks.
An index can be either a usize, a Range or a RangeInclusive. Note that this method takes an array, so all indices must be of the same type. If passed an array of usizes this method gives back an array of mutable references to single elements, while if passed an array of ranges it gives back an array of mutable references to slices.
For a safe alternative see get_disjoint_mut.
§Safety
Calling this method with overlapping or out-of-bounds indices is _undefined behavior_even if the resulting references are not used.
§Examples
let x = &mut [1, 2, 4];
unsafe {
let [a, b] = x.get_disjoint_unchecked_mut([0, 2]);
*a *= 10;
*b *= 100;
}
assert_eq!(x, &[10, 2, 400]);
unsafe {
let [a, b] = x.get_disjoint_unchecked_mut([0..1, 1..3]);
a[0] = 8;
b[0] = 88;
b[1] = 888;
}
assert_eq!(x, &[8, 88, 888]);
unsafe {
let [a, b] = x.get_disjoint_unchecked_mut([1..=2, 0..=0]);
a[0] = 11;
a[1] = 111;
b[0] = 1;
}
assert_eq!(x, &[1, 11, 111]);1.86.0 · Source
Returns mutable references to many indices at once.
An index can be either a usize, a Range or a RangeInclusive. Note that this method takes an array, so all indices must be of the same type. If passed an array of usizes this method gives back an array of mutable references to single elements, while if passed an array of ranges it gives back an array of mutable references to slices.
Returns an error if any index is out-of-bounds, or if there are overlapping indices. An empty range is not considered to overlap if it is located at the beginning or at the end of another range, but is considered to overlap if it is located in the middle.
This method does a O(n^2) check to check that there are no overlapping indices, so be careful when passing many indices.
§Examples
let v = &mut [1, 2, 3];
if let Ok([a, b]) = v.get_disjoint_mut([0, 2]) {
*a = 413;
*b = 612;
}
assert_eq!(v, &[413, 2, 612]);
if let Ok([a, b]) = v.get_disjoint_mut([0..1, 1..3]) {
a[0] = 8;
b[0] = 88;
b[1] = 888;
}
assert_eq!(v, &[8, 88, 888]);
if let Ok([a, b]) = v.get_disjoint_mut([1..=2, 0..=0]) {
a[0] = 11;
a[1] = 111;
b[0] = 1;
}
assert_eq!(v, &[1, 11, 111]);🔬This is a nightly-only experimental API. (substr_range)
Returns the index that an element reference points to.
Returns None if element does not point to the start of an element within the slice.
This method is useful for extending slice iterators like slice::split.
Note that this uses pointer arithmetic and does not compare elements. To find the index of an element via comparison, use.iter().position() instead.
§Panics
Panics if T is zero-sized.
§Examples
Basic usage:
#![feature(substr_range)]
let nums: &[u32] = &[1, 7, 1, 1];
let num = &nums[2];
assert_eq!(num, &1);
assert_eq!(nums.element_offset(num), Some(2));Returning None with an unaligned element:
#![feature(substr_range)]
let arr: &[[u32; 2]] = &[[0, 1], [2, 3]];
let flat_arr: &[u32] = arr.as_flattened();
let ok_elm: &[u32; 2] = flat_arr[0..2].try_into().unwrap();
let weird_elm: &[u32; 2] = flat_arr[1..3].try_into().unwrap();
assert_eq!(ok_elm, &[0, 1]);
assert_eq!(weird_elm, &[1, 2]);
assert_eq!(arr.element_offset(ok_elm), Some(0)); // Points to element 0
assert_eq!(arr.element_offset(weird_elm), None); // Points between element 0 and 1🔬This is a nightly-only experimental API. (substr_range)
Returns the range of indices that a subslice points to.
Returns None if subslice does not point within the slice or if it is not aligned with the elements in the slice.
This method does not compare elements. Instead, this method finds the location in the slice thatsubslice was obtained from. To find the index of a subslice via comparison, instead use.windows().position().
This method is useful for extending slice iterators like slice::split.
Note that this may return a false positive (either Some(0..0) or Some(self.len()..self.len())) if subslice has a length of zero and points to the beginning or end of another, separate, slice.
§Panics
Panics if T is zero-sized.
§Examples
Basic usage:
#![feature(substr_range)]
let nums = &[0, 5, 10, 0, 0, 5];
let mut iter = nums
.split(|t| *t == 0)
.map(|n| nums.subslice_range(n).unwrap());
assert_eq!(iter.next(), Some(0..0));
assert_eq!(iter.next(), Some(1..3));
assert_eq!(iter.next(), Some(4..4));
assert_eq!(iter.next(), Some(5..6));1.0.0 · Source
Sorts the slice in ascending order, preserving initial order of equal elements.
This sort is stable (i.e., does not reorder equal elements) and O(n * log(n)) worst-case.
If the implementation of Ord for T does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
When applicable, unstable sorting is preferred because it is generally faster than stable sorting and it doesn’t allocate auxiliary memory. Seesort_unstable. The exception are partially sorted slices, which may be better served with slice::sort.
Sorting types that only implement PartialOrd such as f32 and f64 require additional precautions. For example, f32::NAN != f32::NAN, which doesn’t fulfill the reflexivity requirement of Ord. By using an alternative comparison function withslice::sort_by such as f32::total_cmp or f64::total_cmp that defines a total order users can sort slices containing floating-point values. Alternatively, if all values in the slice are guaranteed to be in a subset for which PartialOrd::partial_cmp forms atotal order, it’s possible to sort the slice with sort_by(|a, b| a.partial_cmp(b).unwrap()).
§Current implementation
The current implementation is based on driftsort by Orson Peters and Lukas Bergdoll, which combines the fast average case of quicksort with the fast worst case and partial run detection of mergesort, achieving linear time on fully sorted and reversed inputs. On inputs with k distinct elements, the expected time to sort the data is O(n * log(k)).
The auxiliary memory allocation behavior depends on the input length. Short slices are handled without allocation, medium sized slices allocate self.len() and beyond that it clamps at self.len() / 2.
§Panics
May panic if the implementation of Ord for T does not implement a total order, or if the Ord implementation itself panics.
All safe functions on slices preserve the invariant that even if the function panics, all original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. This ensures that recovery code (for instance inside of a Drop or following a catch_unwind) will still have access to all the original elements. For instance, if the slice belongs to a Vec, the Vec::drop method will be able to dispose of all contained elements.
§Examples
let mut v = [4, -5, 1, -3, 2];
v.sort();
assert_eq!(v, [-5, -3, 1, 2, 4]);1.0.0 · Source
Sorts the slice in ascending order with a comparison function, preserving initial order of equal elements.
This sort is stable (i.e., does not reorder equal elements) and O(n * log(n)) worst-case.
If the comparison function compare does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
For example |a, b| (a - b).cmp(a) is a comparison function that is neither transitive nor reflexive nor total, a < b < c < a with a = 1, b = 2, c = 3. For more information and examples see the Ord documentation.
§Current implementation
The current implementation is based on driftsort by Orson Peters and Lukas Bergdoll, which combines the fast average case of quicksort with the fast worst case and partial run detection of mergesort, achieving linear time on fully sorted and reversed inputs. On inputs with k distinct elements, the expected time to sort the data is O(n * log(k)).
The auxiliary memory allocation behavior depends on the input length. Short slices are handled without allocation, medium sized slices allocate self.len() and beyond that it clamps at self.len() / 2.
§Panics
May panic if compare does not implement a total order, or if compare itself panics.
All safe functions on slices preserve the invariant that even if the function panics, all original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. This ensures that recovery code (for instance inside of a Drop or following a catch_unwind) will still have access to all the original elements. For instance, if the slice belongs to a Vec, the Vec::drop method will be able to dispose of all contained elements.
§Examples
let mut v = [4, -5, 1, -3, 2];
v.sort_by(|a, b| a.cmp(b));
assert_eq!(v, [-5, -3, 1, 2, 4]);
// reverse sorting
v.sort_by(|a, b| b.cmp(a));
assert_eq!(v, [4, 2, 1, -3, -5]);1.7.0 · Source
Sorts the slice in ascending order with a key extraction function, preserving initial order of equal elements.
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).
If the implementation of Ord for K does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
§Current implementation
The current implementation is based on driftsort by Orson Peters and Lukas Bergdoll, which combines the fast average case of quicksort with the fast worst case and partial run detection of mergesort, achieving linear time on fully sorted and reversed inputs. On inputs with k distinct elements, the expected time to sort the data is O(n * log(k)).
The auxiliary memory allocation behavior depends on the input length. Short slices are handled without allocation, medium sized slices allocate self.len() and beyond that it clamps at self.len() / 2.
§Panics
May panic if the implementation of Ord for K does not implement a total order, or if the Ord implementation or the key-function f panics.
All safe functions on slices preserve the invariant that even if the function panics, all original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. This ensures that recovery code (for instance inside of a Drop or following a catch_unwind) will still have access to all the original elements. For instance, if the slice belongs to a Vec, the Vec::drop method will be able to dispose of all contained elements.
§Examples
let mut v = [4i32, -5, 1, -3, 2];
v.sort_by_key(|k| k.abs());
assert_eq!(v, [1, 2, -3, 4, -5]);1.34.0 · Source
Sorts the slice in ascending order with a key extraction function, preserving initial order of equal elements.
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).
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.
If the implementation of Ord for K does not implement a total order, the function may panic; even if the function exits normally, the resulting order of elements in the slice is unspecified. See also the note on panicking below.
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 implementation is based on instruction-parallel-network sort by Lukas Bergdoll, which combines the fast average case of randomized quicksort with the fast worst case of heapsort, while achieving linear time on fully sorted and reversed inputs. And_O_(k * log(n)) where k is the number of distinct elements in the input. It leverages superscalar out-of-order execution capabilities commonly found in CPUs, to efficiently perform the operation.
In the worst case, the algorithm allocates temporary storage in a Vec<(K, usize)> the length of the slice.
§Panics
May panic if the implementation of Ord for K does not implement a total order, or if the Ord implementation panics.
All safe functions on slices preserve the invariant that even if the function panics, all original elements will remain in the slice and any possible modifications via interior mutability are observed in the input. This ensures that recovery code (for instance inside of a Drop or following a catch_unwind) will still have access to all the original elements. For instance, if the slice belongs to a Vec, the Vec::drop method will be able to dispose of all contained elements.
§Examples
let mut v = [4i32, -5, 1, -3, 2, 10];
// Strings are sorted by lexicographical order.
v.sort_by_cached_key(|k| k.to_string());
assert_eq!(v, [-3, -5, 1, 10, 2, 4]);1.0.0 · Source
Copies self into a new Vec.
§Examples
let s = [10, 40, 30];
let x = s.to_vec();
// Here, `s` and `x` can be modified independently.🔬This is a nightly-only experimental API. (allocator_api)
Copies self into a new Vec with an allocator.
§Examples
#![feature(allocator_api)]
use std::alloc::System;
let s = [10, 40, 30];
let x = s.to_vec_in(System);
// Here, `s` and `x` can be modified independently.1.40.0 · Source
Creates a vector by copying a slice n times.
§Panics
This function will panic if the capacity would overflow.
§Examples
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
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
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
👎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]);Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.