#[repr(transparent)]pub struct ByteStr(pub [u8]);
bstr
A wrapper for &[u8] representing a human-readable string that’s conventionally, but not always, UTF-8.
&[u8]
Unlike &str, this type permits non-UTF-8 contents, making it suitable for user input, non-native filenames (as Path only supports native filenames), and other applications that need to round-trip whatever data the user provides.
&str
Path
For an owned, growable byte string buffer, use ByteString.
ByteString
ByteStr implements Deref to [u8], so all methods available on [u8] are available on ByteStr.
ByteStr
Deref
[u8]
A &ByteStr has the same representation as a &str. That is, a &ByteStr is a wide pointer which includes a pointer to some bytes and a length.
&ByteStr
The ByteStr type has a number of trait implementations, and in particular, defines equality and comparisons between &ByteStr, &str, and &[u8], for convenience.
The Debug implementation for ByteStr shows its bytes as a normal string, with invalid UTF-8 presented as hex escape sequences.
Debug
The Display implementation behaves as if the ByteStr were first lossily converted to a str, with invalid UTF-8 presented as the Unicode replacement character (�).
Display
str
0: [u8]
Creates a ByteStr slice from anything that can be converted to a byte slice.
This is a zero-cost conversion.
You can create a ByteStr from a byte array, a byte slice or a string slice:
let a = ByteStr::new(b"abc"); let b = ByteStr::new(&b"abc"[..]); let c = ByteStr::new("abc"); assert_eq!(a, b); assert_eq!(a, c);
Checks if all bytes in this slice are within the ASCII range.
An empty slice returns true.
true
ascii_char
If this slice is_ascii, returns it as a slice of ASCII characters, otherwise returns None.
is_ascii
None
Converts this slice of bytes into a slice of ASCII characters, without checking whether they’re valid.
Every byte in the slice must be in 0..=127, or else this is UB.
0..=127
Checks that two slices are an ASCII case-insensitive match.
Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.
to_ascii_lowercase(a) == to_ascii_lowercase(b)
Converts this slice to its ASCII upper case equivalent in-place.
ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.
To return a new uppercased value without modifying the existing one, use to_ascii_uppercase.
to_ascii_uppercase
Converts this slice to its ASCII lower case equivalent in-place.
ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.
To return a new lowercased value without modifying the existing one, use to_ascii_lowercase.
to_ascii_lowercase
Returns an iterator that produces an escaped version of this slice, treating it as an ASCII string.
let s = b"0\t\r\n'\"\\\x9d"; let escaped = s.escape_ascii().to_string(); assert_eq!(escaped, "0\\t\\r\\n\\'\\\"\\\\\\x9d");
Returns a byte slice with leading ASCII whitespace bytes removed.
‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.
u8::is_ascii_whitespace
assert_eq!(b" \t hello world\n".trim_ascii_start(), b"hello world\n"); assert_eq!(b" ".trim_ascii_start(), b""); assert_eq!(b"".trim_ascii_start(), b"");
Returns a byte slice with trailing ASCII whitespace bytes removed.
assert_eq!(b"\r hello world\n ".trim_ascii_end(), b"\r hello world"); assert_eq!(b" ".trim_ascii_end(), b""); assert_eq!(b"".trim_ascii_end(), b"");
Returns a byte slice with leading and trailing ASCII whitespace bytes removed.
assert_eq!(b"\r hello world\n ".trim_ascii(), b"hello world"); assert_eq!(b" ".trim_ascii(), b""); assert_eq!(b"".trim_ascii(), b"");
Returns the number of elements in the slice.
let a = [1, 2, 3]; assert_eq!(a.len(), 3);
Returns true if the slice has a length of 0.
let a = [1, 2, 3]; assert!(!a.is_empty()); let b: &[i32] = &[]; assert!(b.is_empty());
Returns the first element of the slice, or None if it is empty.
let v = [10, 40, 30]; assert_eq!(Some(&10), v.first()); let w: &[i32] = &[]; assert_eq!(None, w.first());
Returns a mutable reference to the first element of the slice, or None if it is empty.
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());
Returns the first and all the rest of the elements of the slice, or None if it is empty.
let x = &[0, 1, 2]; if let Some((first, elements)) = x.split_first() { assert_eq!(first, &0); assert_eq!(elements, &[1, 2]); }
let x = &mut [0, 1, 2]; if let Some((first, elements)) = x.split_first_mut() { *first = 3; elements[0] = 4; elements[1] = 5; } assert_eq!(x, &[3, 4, 5]);
Returns the last and all the rest of the elements of the slice, or None if it is empty.
let x = &[0, 1, 2]; if let Some((last, elements)) = x.split_last() { assert_eq!(last, &2); assert_eq!(elements, &[0, 1]); }
let x = &mut [0, 1, 2]; if let Some((last, elements)) = x.split_last_mut() { *last = 3; elements[0] = 4; elements[1] = 5; } assert_eq!(x, &[4, 5, 3]);
Returns the last element of the slice, or None if it is empty.
let v = [10, 40, 30]; assert_eq!(Some(&30), v.last()); let w: &[i32] = &[]; assert_eq!(None, w.last());
Returns a mutable reference to the last item in the slice, or None if it is empty.
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());
Returns an array reference to the first N items in the slice.
N
If the slice is not at least N in length, this will return None.
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>());
Returns a mutable array reference to the first N items in the slice.
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>());
Returns an array reference to the first N items in the slice and the remaining slice.
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>());
Returns a mutable array reference to the first N items in the slice and the remaining slice.
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>());
Returns an array reference to the last N items in the slice and the remaining slice.
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>());
Returns a mutable array reference to the last N items in the slice and the remaining slice.
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>());
Returns an array reference to the last N items in the slice.
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>());
Returns a mutable array reference to the last N items in the slice.
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>());
Returns a reference to an element or subslice depending on the type of index.
let v = [10, 40, 30]; assert_eq!(Some(&40), v.get(1)); assert_eq!(Some(&[10, 40][..]), v.get(0..2)); assert_eq!(None, v.get(3)); assert_eq!(None, v.get(0..4));
Returns a mutable reference to an element or subslice depending on the type of index (see get) or None if the index is out of bounds.
get
let x = &mut [0, 1, 2]; if let Some(elem) = x.get_mut(1) { *elem = 42; } assert_eq!(x, &[0, 42, 2]);
Returns a reference to an element or subslice, without doing bounds checking.
For a safe alternative see get.
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.
.get(index).unwrap_unchecked()
.get_unchecked(len)
.get_unchecked(..len + 1)
.get_unchecked(..=len)
let x = &[1, 2, 4]; unsafe { assert_eq!(x.get_unchecked(1), &2); }
Returns a mutable reference to an element or subslice, without doing bounds checking.
For a safe alternative see get_mut.
get_mut
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.
.get_mut(index).unwrap_unchecked()
.get_unchecked_mut(len)
.get_unchecked_mut(..len + 1)
.get_unchecked_mut(..=len)
let x = &mut [1, 2, 4]; unsafe { let elem = x.get_unchecked_mut(1); *elem = 13; } assert_eq!(x, &[1, 13, 4]);
Returns a raw pointer to the slice’s buffer.
The caller must ensure that the slice outlives the pointer this function returns, or else it will end up 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.
UnsafeCell
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.
let x = &[1, 2, 4]; let x_ptr = x.as_ptr(); unsafe { for i in 0..x.len() { assert_eq!(x.get_unchecked(i), &*x_ptr.add(i)); } }
Returns an unsafe mutable pointer to the slice’s buffer.
let x = &mut [1, 2, 4]; let x_ptr = x.as_mut_ptr(); unsafe { for i in 0..x.len() { *x_ptr.add(i) += 2; } } assert_eq!(x, &[3, 4, 6]);
Returns the two raw pointers spanning the slice.
The returned range is half-open, which means that the end pointer points one past the last element of the slice. This way, an empty slice is represented by two equal pointers, and the difference between the two pointers represents the size of the slice.
See as_ptr for warnings on using these pointers. The end pointer requires extra caution, as it does not point to a valid element in the slice.
as_ptr
This function is useful for interacting with foreign interfaces which use two pointers to refer to a range of elements in memory, as is common in C++.
It can also be useful to check if a pointer to an element refers to an element of this slice:
let a = [1, 2, 3]; let x = &a[1] as *const _; let y = &5 as *const _; assert!(a.as_ptr_range().contains(&x)); assert!(!a.as_ptr_range().contains(&y));
Returns the two unsafe mutable pointers spanning the slice.
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.
slice_as_array
Gets a reference to the underlying array.
If N is not exactly equal to the length of self, then this method returns None.
self
Gets a mutable reference to the slice’s underlying array.
Swaps two elements in the slice.
If a equals to b, it’s guaranteed that elements won’t change value.
a
b
Panics if a or b are out of bounds.
let mut v = ["a", "b", "c", "d", "e"]; v.swap(2, 4); assert!(v == ["a", "b", "e", "d", "c"]);
Swaps two elements in the slice, without doing bounds checking.
For a safe alternative see swap.
swap
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().
a < self.len()
b < self.len()
#![feature(slice_swap_unchecked)] let mut v = ["a", "b", "c", "d"]; / SAFETY: we know that 1 and 3 are both indices of the slice unsafe { v.swap_unchecked(1, 3) }; assert!(v == ["a", "d", "c", "b"]);
Reverses the order of elements in the slice, in place.
let mut v = [1, 2, 3]; v.reverse(); assert!(v == [3, 2, 1]);
Returns an iterator over the slice.
The iterator yields all items from start to end.
let x = &[1, 2, 4]; let mut iterator = x.iter(); assert_eq!(iterator.next(), Some(&1)); assert_eq!(iterator.next(), Some(&2)); assert_eq!(iterator.next(), Some(&4)); assert_eq!(iterator.next(), None);
Returns an iterator that allows modifying each value.
let x = &mut [1, 2, 4]; for elem in x.iter_mut() { *elem += 2; } assert_eq!(x, &[3, 4, 6]);
Returns an iterator over all contiguous windows of length size. The windows overlap. If the slice is shorter than size, the iterator returns no values.
size
Panics if size is zero.
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']; 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 use Cell::as_slice_of_cells in conjunction with windows instead:
windows_mut
windows
[0,1,2].windows_mut(2).collect()
Cell::as_slice_of_cells
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']);
Returns an iterator over chunk_size elements of the slice at a time, starting at the beginning of the slice.
chunk_size
The chunks are slices and do not overlap. If chunk_size does not divide the length of the slice, then the last chunk will not have length chunk_size.
See chunks_exact for a variant of this iterator that returns chunks of always exactly chunk_size elements, and rchunks for the same iterator but starting at the end of the slice.
chunks_exact
rchunks
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.
as_chunks
Panics if chunk_size is zero.
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());
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.
chunks_exact_mut
rchunks_mut
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.
as_chunks_mut
let v = &mut [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, 3]);
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.
chunk_size-1
remainder
Due to each chunk having exactly chunk_size elements, the compiler can often optimize the resulting code better than in the case of chunks.
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.
rchunks_exact
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']);
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.
into_remainder
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.
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.
rchunks_exact_mut
let v = &mut [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, 0]);
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_flattened
As this is unsafe, consider whether you could use as_chunks or as_rchunks instead, perhaps via something like if let (chunks, []) = slice.as_chunks() or let (chunks, []) = slice.as_chunks() else { unreachable!() };.
unsafe
as_rchunks
if let (chunks, []) = slice.as_chunks()
let (chunks, []) = slice.as_chunks() else { unreachable!() };
This may only be called when
self.len() % N == 0
N != 0
let slice: &[char] = &['l', 'o', 'r', 'e', 'm', '!']; let chunks: &[[char; 1]] = / SAFETY: 1-element chunks never have remainder unsafe { slice.as_chunks_unchecked() }; assert_eq!(chunks, &[['l'], ['o'], ['r'], ['e'], ['m'], ['!']]); let chunks: &[[char; 3]] = / SAFETY: The slice length (6) is a multiple of 3 unsafe { slice.as_chunks_unchecked() }; assert_eq!(chunks, &[['l', 'o', 'r'], ['e', 'm', '!']]); / These would be unsound: / let chunks: &[[_; 5]] = slice.as_chunks_unchecked() / The slice length is not a multiple of 5 / let chunks: &[[_; 0]] = slice.as_chunks_unchecked() / Zero-length chunks are never allowed
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. Given let (chunks, remainder) = slice.as_chunks(), then:
let (chunks, remainder) = slice.as_chunks()
chunks.len()
slice.len() / N
remainder.len()
slice.len() % N
slice.len()
chunks.len() * N + remainder.len()
You can flatten the chunks back into a slice-of-T with as_flattened.
T
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.
let slice = ['l', 'o', 'r', 'e', 'm']; let (chunks, remainder) = slice.as_chunks(); assert_eq!(chunks, &[['l', 'o'], ['r', 'e']]); assert_eq!(remainder, &['m']);
If you expect the slice to be an exact multiple, you can combine let-else with an empty slice pattern:
let
else
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']]);
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. Given let (remainder, chunks) = slice.as_rchunks(), then:
let (remainder, chunks) = slice.as_rchunks()
let slice = ['l', 'o', 'r', 'e', 'm']; let (remainder, chunks) = slice.as_rchunks(); assert_eq!(remainder, &['l']); assert_eq!(chunks, &[['o', 'r'], ['e', 'm']]);
This is the inverse operation to as_flattened_mut.
as_flattened_mut
As this is unsafe, consider whether you could use as_chunks_mut or as_rchunks_mut instead, perhaps via something like if let (chunks, []) = slice.as_chunks_mut() or let (chunks, []) = slice.as_chunks_mut() else { unreachable!() };.
as_rchunks_mut
if let (chunks, []) = slice.as_chunks_mut()
let (chunks, []) = slice.as_chunks_mut() else { unreachable!() };
let slice: &mut [char] = &mut ['l', 'o', 'r', 'e', 'm', '!']; let chunks: &mut [[char; 1]] = / SAFETY: 1-element chunks never have remainder unsafe { slice.as_chunks_unchecked_mut() }; chunks[0] = ['L']; assert_eq!(chunks, &[['L'], ['o'], ['r'], ['e'], ['m'], ['!']]); let chunks: &mut [[char; 3]] = / SAFETY: The slice length (6) is a multiple of 3 unsafe { slice.as_chunks_unchecked_mut() }; chunks[1] = ['a', 'x', '?']; assert_eq!(slice, &['L', 'o', 'r', 'a', 'x', '?']); / These would be unsound: / let chunks: &[[_; 5]] = slice.as_chunks_unchecked_mut() / The slice length is not a multiple of 5 / let chunks: &[[_; 0]] = slice.as_chunks_unchecked_mut() / Zero-length chunks are never allowed
The remainder is meaningful in the division sense. Given let (chunks, remainder) = slice.as_chunks_mut(), then:
let (chunks, remainder) = slice.as_chunks_mut()
You can flatten the chunks back into a slice-of-T with as_flattened_mut.
let v = &mut [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, 9]);
The remainder is meaningful in the division sense. Given let (remainder, chunks) = slice.as_rchunks_mut(), then:
let (remainder, chunks) = slice.as_rchunks_mut()
let v = &mut [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, 2]);
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 if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
#![feature(array_windows)] let slice = [0, 1, 2, 3]; let mut iter = slice.array_windows(); assert_eq!(iter.next().unwrap(), &[0, 1]); assert_eq!(iter.next().unwrap(), &[1, 2]); assert_eq!(iter.next().unwrap(), &[2, 3]); assert!(iter.next().is_none());
Returns an iterator over chunk_size elements of the slice at a time, starting at the end of the slice.
See rchunks_exact for a variant of this iterator that returns chunks of always exactly chunk_size elements, and chunks for the same iterator but starting at the beginning of the slice.
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.
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());
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.
let v = &mut [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, 1]);
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.
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']);
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.
let v = &mut [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, 1]);
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.
slice[0]
slice[1]
slice[2]
let slice = &[1, 1, 3, 2]; let mut iter = slice.chunk_by(|a, b| a == b); assert_eq!(iter.next(), Some(&[1, 1][..])); assert_eq!(iter.next(), Some(&[3, 3][..])); assert_eq!(iter.next(), Some(&[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);
Returns an iterator over the slice producing non-overlapping mutable runs of elements using the predicate to separate them.
let slice = &mut [1, 1, 3, 2]; let mut iter = slice.chunk_by_mut(|a, b| a == b); assert_eq!(iter.next(), Some(&mut [1, 1][..])); assert_eq!(iter.next(), Some(&mut [3, 3][..])); assert_eq!(iter.next(), Some(&mut [2, 2][..])); assert_eq!(iter.next(), None);
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);
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).
[0, mid)
mid
[mid, len)
len
Panics if mid > len. For a non-panicking alternative see split_at_checked.
mid > len
split_at_checked
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, []); }
Divides one mutable slice into two at an index.
Panics if mid > len. For a non-panicking alternative see split_at_mut_checked.
split_at_mut_checked
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]);
Divides one slice into two at an index, without doing bounds checking.
For a safe alternative see split_at.
split_at
Calling this method with an out-of-bounds index is undefined behavior even if the resulting reference is not used. The caller has to ensure that 0 <= mid <= self.len().
0 <= mid <= self.len()
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, []); }
Divides one mutable slice into two at an index, without doing bounds checking.
For a safe alternative see split_at_mut.
split_at_mut
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]);
Divides one slice into two at an index, returning None if the slice is too short.
If mid ≤ len returns a pair of slices where the first will contain all indices from [0, mid) (excluding the index mid itself) and the second will contain all indices from [mid, len) (excluding the index len itself).
mid ≤ len
Otherwise, if mid > len, returns None.
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));
Divides one mutable slice into two at an index, returning None if the slice is too short.
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));
Returns an iterator over subslices separated by elements that match pred. The matched element is not contained in the subslices.
pred
let slice = [10, 40, 33, 20]; let mut iter = slice.split(|num| num % 3 == 0); assert_eq!(iter.next().unwrap(), &[10, 40]); assert_eq!(iter.next().unwrap(), &[20]); assert!(iter.next().is_none());
If the first element is matched, an empty slice will be the first item returned by the iterator. Similarly, if the last element in the slice is matched, an empty slice will be the last item returned by the iterator:
let slice = [10, 40, 33]; let mut iter = slice.split(|num| num % 3 == 0); assert_eq!(iter.next().unwrap(), &[10, 40]); assert_eq!(iter.next().unwrap(), &[]); assert!(iter.next().is_none());
If two matched elements are directly adjacent, an empty slice will be present between them:
let slice = [10, 6, 33, 20]; let mut iter = slice.split(|num| num % 3 == 0); assert_eq!(iter.next().unwrap(), &[10]); assert_eq!(iter.next().unwrap(), &[]); assert_eq!(iter.next().unwrap(), &[20]); assert!(iter.next().is_none());
Returns an iterator over mutable subslices separated by elements that match pred. The matched element is not contained in the subslices.
let mut v = [10, 40, 30, 20, 60, 50]; for group in v.split_mut(|num| *num % 3 == 0) { group[0] = 1; } assert_eq!(v, [1, 40, 30, 1, 60, 1]);
Returns an iterator over subslices separated by elements that match pred. The matched element is contained in the end of the previous subslice as a terminator.
let slice = [10, 40, 33, 20]; let mut iter = slice.split_inclusive(|num| num % 3 == 0); assert_eq!(iter.next().unwrap(), &[10, 40, 33]); assert_eq!(iter.next().unwrap(), &[20]); assert!(iter.next().is_none());
If the last element of the slice is matched, that element will be considered the terminator of the preceding slice. That slice will be the last item returned by the iterator.
let slice = [3, 10, 40, 33]; let mut iter = slice.split_inclusive(|num| num % 3 == 0); assert_eq!(iter.next().unwrap(), &[3]); assert_eq!(iter.next().unwrap(), &[10, 40, 33]); assert!(iter.next().is_none());
Returns an iterator over mutable subslices separated by elements that match pred. The matched element is contained in the previous subslice as a terminator.
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]);
Returns an iterator over subslices separated by elements that match pred, starting at the end of the slice and working backwards. The matched element is not contained in the subslices.
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.
split()
let v = &[0, 1, 2, 3, 5, 8]; let mut it = v.rsplit(|n| *n % 2 == 0); assert_eq!(it.next().unwrap(), &[]); assert_eq!(it.next().unwrap(), &[3, 5]); assert_eq!(it.next().unwrap(), &[1, 1]); assert_eq!(it.next().unwrap(), &[]); assert_eq!(it.next(), None);
Returns an iterator over mutable subslices separated by elements that match pred, starting at the end of the slice and working backwards. The matched element is not contained in the subslices.
let mut v = [100, 400, 300, 200, 600, 500]; let mut count = 0; for group in v.rsplit_mut(|num| *num % 3 == 0) { count += 1; group[0] = count; } assert_eq!(v, [3, 400, 300, 2, 600, 1]);
Returns an iterator over subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.
n
The last element returned, if any, will contain the remainder of the slice.
Print the slice split once by numbers divisible by 3 (i.e., [10, 40], [20, 60, 50]):
[10, 40]
[20, 60, 50]
let v = [10, 40, 30, 20, 60, 50]; for group in v.splitn(2, |num| *num % 3 == 0) { println!("{group:?}"); }
Returns an iterator over mutable subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.
let mut v = [10, 40, 30, 20, 60, 50]; for group in v.splitn_mut(2, |num| *num % 3 == 0) { group[0] = 1; } assert_eq!(v, [1, 40, 30, 1, 60, 50]);
Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.
Print the slice split once, starting from the end, by numbers divisible by 3 (i.e., [50], [10, 40, 30, 20]):
[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:?}"); }
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]);
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.
#![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);
Splits the slice on the last element that matches the specified predicate.
#![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);
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.
binary_search
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:
&T
String
PartialEq<str>
iter().any
let v = [String::from("hello"), String::from("world")]; / slice of `String` assert!(v.iter().any(|e| e == "hello")); / search with `&str` assert!(!v.iter().any(|e| e == "hi"));
Returns true if needle is a prefix of the slice or equal to the slice.
needle
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(&[]));
Returns true if needle is a suffix of the slice or equal to the slice.
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]));
let v = &[10, 40, 30]; assert!(v.ends_with(&[])); let v: &[u8] = &[]; assert!(v.ends_with(&[]));
Returns a subslice with the prefix removed.
If the slice starts with prefix, returns the subslice after the prefix, wrapped in Some. If prefix is empty, simply returns the original slice. If prefix is equal to the original slice, returns an empty slice.
prefix
Some
If the slice does not start with prefix, returns None.
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()));
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.
suffix
If the slice does not end with suffix, returns None.
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);
trim_prefix_suffix
Returns a subslice with the optional prefix removed.
If the slice starts with prefix, returns the subslice after the prefix. If prefix is 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.
#![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());
Returns a subslice with the optional suffix removed.
If the slice ends with suffix, returns the subslice before the suffix. If suffix is 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.
#![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][..]);
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.
Result::Ok
Result::Err
See also binary_search_by, binary_search_by_key, and partition_point.
binary_search_by
binary_search_by_key
partition_point
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].
[1, 4]
let s = [0, 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, 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, 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, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
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.
Less
Equal
Greater
See also binary_search, binary_search_by_key, and partition_point.
let s = [0, 1, 2, 3, 5, 8, 13, 21, 34, 55]; let seek = 13; assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9)); let seek = 4; assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7)); let seek = 100; assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13)); let seek = 1; let r = s.binary_search_by(|probe| probe.cmp(&seek)); assert!(match r { Ok(1..=4) => true, _ => false, });
Binary searches this slice with a key extraction function.
Assumes that the slice is sorted by the key, for instance with sort_by_key using the same key extraction function. If the slice is not sorted by the key, the returned result is unspecified and meaningless.
sort_by_key
See also binary_search, binary_search_by, and partition_point.
Looks up a series of four elements in a slice of pairs sorted by their second elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].
let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1), (1, 2), (2, 3), (4, 5), (5, 8), (3, 13), (1, 21), (2, 34), (4, 55)]; assert_eq!(s.binary_search_by_key(&13, |&(a, b)| b), Ok(9)); assert_eq!(s.binary_search_by_key(&4, |&(a, b)| b), Err(7)); assert_eq!(s.binary_search_by_key(&100, |&(a, b)| b), Err(13)); let r = s.binary_search_by_key(&1, |&(a, b)| b); assert!(match r { Ok(1..=4) => true, _ => false, });
Sorts the slice 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.
Ord
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.
|a, b| (a - b).cmp(a)
a < b < c < a
a = 1, b = 2, c = 3
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 with slice::sort_unstable_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 a total order, it’s possible to sort the slice with sort_unstable_by(|a, b| a.partial_cmp(b).unwrap()).
PartialOrd
f32
f64
f32::NAN != f32::NAN
slice::sort_unstable_by
f32::total_cmp
f64::total_cmp
PartialOrd::partial_cmp
sort_unstable_by(|a, b| a.partial_cmp(b).unwrap())
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.
May panic if the implementation of Ord for T does not implement a total order, or if the Ord implementation panics.
let mut v = [4, -5, 1, -3, 2]; v.sort_unstable(); assert_eq!(v, [-5, -3, 1, 2, 4]);
Sorts the slice in ascending order with a comparison function, without preserving the initial order of equal elements.
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.
compare
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.
May panic if the compare does not implement a total order, or if the compare itself panics.
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]);
Sorts the slice in ascending order with a key extraction function, without preserving the initial order of equal elements.
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.
K
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.
May panic if the implementation of Ord for K does not implement a total order, or if the Ord implementation panics.
let mut v = [4i32, -5, 1, -3, 2]; v.sort_unstable_by_key(|k| k.abs()); assert_eq!(v, [1, 2, -3, 4, -5]);
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.
index
<=
>=
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 satisfy x <= self[index].
x <= self[index]
The element at index.
The unsorted subslice after index, whose elements all satisfy x >= self[index].
x >= self[index]
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.
sort_unstable
Panics when index >= len(), and so always panics on empty slices.
index >= len()
May panic if the implementation of Ord for T does not implement a total order.
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]);
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.
Returns a triple partitioning the reordered slice:
The unsorted subslice before index, whose elements all satisfy compare(x, self[index]).is_le().
compare(x, self[index]).is_le()
The unsorted subslice after index, whose elements all satisfy compare(x, self[index]).is_ge().
compare(x, self[index]).is_ge()
May panic if compare does not implement a total order.
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]);
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.
The unsorted subslice before index, whose elements all satisfy f(x) <= f(self[index]).
f(x) <= f(self[index])
The unsorted subslice after index, whose elements all satisfy f(x) >= f(self[index]).
f(x) >= f(self[index])
Panics when index >= len(), meaning it always panics on empty slices.
May panic if K: Ord does not implement a total order.
K: Ord
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]);
slice_partition_dedup
Moves all consecutive repeated elements to the end of the slice according to the PartialEq trait implementation.
PartialEq
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.
#![feature(slice_partition_dedup)] let mut slice = [1, 2, 3, 2, 1]; let (dedup, duplicates) = slice.partition_dedup(); assert_eq!(dedup, [1, 2, 3, 2, 1]); assert_eq!(duplicates, [2, 3, 1]);
Moves all but the first of consecutive elements to the end of the slice satisfying a given equality relation.
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.
same_bucket
same_bucket(a, b)
#![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"]);
Moves all but the first of consecutive elements to the end of the slice that resolve to the same key.
#![feature(slice_partition_dedup)] let mut slice = [10, 20, 21, 30, 20, 11, 13]; let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10); assert_eq!(dedup, [10, 20, 30, 20, 11]); assert_eq!(duplicates, [21, 30, 13]);
Rotates the slice in-place such that the first mid elements of the slice move to the end while the last self.len() - mid elements move to the front.
self.len() - mid
After calling rotate_left, the element previously at index mid will become the first element in the slice.
rotate_left
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.
mid == self.len()
Takes linear (in self.len()) time.
self.len()
let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; a.rotate_left(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
Rotating a subslice:
let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; a[1..5].rotate_left(1); assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
Rotates the slice in-place such that the first self.len() - k elements of the slice move to the end while the last k elements move to the front.
self.len() - k
k
After calling rotate_right, the element previously at index self.len() - k will become the first element in the slice.
rotate_right
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.
k == self.len()
let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; a.rotate_right(2); assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; a[1..5].rotate_right(1); assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
Fills self with elements by cloning value.
value
let mut buf = vec![0; 10]; buf.fill(1); assert_eq!(buf, vec![1; 10]);
Fills self with elements returned by calling a closure repeatedly.
This method uses a closure to create new values. If you’d rather Clone a given value, use fill. If you want to use the Default trait to generate values, you can pass Default::default as the argument.
Clone
fill
Default
Default::default
let mut buf = vec![1; 10]; buf.fill_with(Default::default); assert_eq!(buf, vec![0; 10]);
Copies the elements from src into self.
src
The length of src must be the same as self.
This function will panic if the two slices have different lengths.
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:
clone_from_slice
let mut slice = [1, 2, 3, 4, 5]; slice[..2].clone_from_slice(&slice[3..]); / compile fail!
To work around this, we can use split_at_mut to create two distinct sub-slices from a slice:
let mut slice = [1, 2, 3, 4, 5]; { let (left, right) = slice.split_at_mut(2); left.clone_from_slice(&right[1..]); } assert_eq!(slice, [4, 5, 3, 4, 5]);
Copies all elements from src into self, using a memcpy.
If T does not implement Copy, use clone_from_slice.
Copy
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:
copy_from_slice
let mut slice = [1, 2, 3, 4, 5]; slice[..2].copy_from_slice(&slice[3..]); / compile fail!
let mut slice = [1, 2, 3, 4, 5]; { let (left, right) = slice.split_at_mut(2); left.copy_from_slice(&right[1..]); } assert_eq!(slice, [4, 5, 3, 4, 5]);
Copies elements from one part of the slice to another part of itself, using a memmove.
src is the range within self to copy from. dest is the starting index of the range within self to copy to, which will have the same length as src. The two ranges may overlap. The ends of the two ranges must be less than or equal to self.len().
dest
This function will panic if either range exceeds the end of the slice, or if the end of src is before the start.
Copying four bytes within a slice:
let mut bytes = *b"Hello, World!"; bytes.copy_within(1..5, 8); assert_eq!(&bytes, b"Hello, Wello!");
Swaps all elements in self with those in other.
other
The length of other must be the same as self.
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]);
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:
swap_with_slice
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]);
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.
U
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.
transmute
transmute::<T, U>
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); }
Transmutes the mutable slice to a mutable slice of another type, ensuring alignment of the types is maintained.
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); }
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.
slice::align_to
This will panic if the size of the SIMD type is different from LANES times that of the scalar.
LANES
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.
Simd<T, LANES>
LANES == 3
#![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);
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.
slice::align_to_mut
This is the mutable version of slice::as_simd; see that for examples.
slice::as_simd
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.
a <= b
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.
Self::Item
false
let empty: [i32; 0] = []; assert!([1, 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());
Checks if the elements of this slice are sorted using the given comparator function.
Instead of using PartialOrd::partial_cmp, this function uses the given compare function to determine whether two elements are to be considered in sorted order.
assert!([1, 2, 9].is_sorted_by(|a, b| a <= b)); assert!(![1, 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));
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.
f
is_sorted
assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len())); assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
Returns the index of the partition point according to the given predicate (the index of the first element of the second partition).
The slice is assumed to be partitioned according to the given predicate. This means that all elements for which the predicate returns true are at the start of the slice and all elements for which the predicate returns false are at the end. For example, [7, 15, 3, 5, 4, 12, 6] is partitioned under the predicate x % 2 != 0 (all odd numbers are at the start, all even at the end).
[7, 15, 3, 5, 4, 12, 6]
x % 2 != 0
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.
let v = [1, 2, 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, 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, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
Removes the subslice corresponding to the given range and returns a reference to it.
Returns None and does not modify the slice if the given range is out of bounds.
Note that this method only accepts one-sided ranges such as 2.. or ..6, but not 2..6.
2..
..6
2..6
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:
range
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));
Removes the subslice corresponding to the given range and returns a mutable reference to it.
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']);
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']);
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));
Removes the first element of the slice and returns a reference to it.
Returns None if the slice is empty.
let mut slice: &[_] = &['a', 'b', 'c']; let first = slice.split_off_first().unwrap(); assert_eq!(slice, &['b', 'c']); assert_eq!(first, &'a');
Removes the first element of the slice and returns a mutable reference to it.
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');
Removes the last element of the slice and returns a reference to it.
let mut slice: &[_] = &['a', 'b', 'c']; let last = slice.split_off_last().unwrap(); assert_eq!(slice, &['a', 'b']); assert_eq!(last, &'c');
Removes the last element of the slice and returns a mutable reference to it.
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');
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.
usize
Range
RangeInclusive
For a safe alternative see get_disjoint_mut.
get_disjoint_mut
Calling this method with overlapping or out-of-bounds indices is undefined behavior even if the resulting references are not used.
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]);
Returns mutable references to many indices at once.
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.
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]);
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.
element
This method is useful for extending slice iterators like slice::split.
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.
.iter().position()
Panics if T is zero-sized.
#![feature(substr_range)] let nums: &[u32] = &[1, 7, 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
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.
subslice
This method does not compare elements. Instead, this method finds the location in the slice that subslice was obtained from. To find the index of a subslice via comparison, instead use .windows().position().
.windows()
.position()
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.
Some(0..0)
Some(self.len()..self.len())
#![feature(substr_range)] let nums = &[0, 5, 10, 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));
Creates an iterator over the contiguous valid UTF-8 ranges of this slice, and the non-UTF-8 fragments in between.
See the Utf8Chunk type for documentation of the items yielded by this iterator.
Utf8Chunk
This function formats arbitrary but mostly-UTF-8 bytes into Rust source code in the form of a C-string literal (c"...").
c"..."
use std::fmt::Write as _; pub fn cstr_literal(bytes: &[u8]) -> String { let mut repr = String::new(); repr.push_str("c\""); for chunk in bytes.utf8_chunks() { for ch in chunk.valid().chars() { / Escapes \0, \t, \r, \n, \\, \', \", and uses \u{...} for non-printable characters. write!(repr, "{}", ch.escape_debug()).unwrap(); } for byte in chunk.invalid() { write!(repr, "\\x{:02X}", byte).unwrap(); } } repr.push('"'); repr } fn main() { let lit = cstr_literal(b"\xferris the \xf0\x9f\xa6\x80\x07"); let expected = stringify!(c"\xFErris the 🦀\u{7}"); assert_eq!(lit, expected); }
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.
When applicable, unstable sorting is preferred because it is generally faster than stable sorting and it doesn’t allocate auxiliary memory. See sort_unstable. The exception are partially sorted slices, which may be better served with slice::sort.
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 with slice::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 a total order, it’s possible to sort the slice with sort_by(|a, b| a.partial_cmp(b).unwrap()).
slice::sort_by
sort_by(|a, b| a.partial_cmp(b).unwrap())
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.
self.len() / 2
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.
Drop
catch_unwind
Vec
Vec::drop
let mut v = [4, -5, 1, -3, 2]; v.sort(); assert_eq!(v, [-5, -3, 1, 2, 4]);
Sorts the slice in ascending order with a comparison function, preserving initial order of equal elements.
May panic if compare does not implement a total order, or if compare itself panics.
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]);
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).
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.
let mut v = [4i32, -5, 1, -3, 2]; v.sort_by_key(|k| k.abs()); assert_eq!(v, [1, 2, -3, 4, -5]);
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.
For simple key functions (e.g., functions that are property accesses or basic operations), sort_by_key is likely to be faster.
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.
Vec<(K, usize)>
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]);
Copies self into a new Vec.
let s = [10, 40, 30]; let x = s.to_vec(); / Here, `s` and `x` can be modified independently.
allocator_api
Copies self into a new Vec with an allocator.
#![feature(allocator_api)] use std::alloc::System; let s = [10, 40, 30]; let x = s.to_vec_in(System); / Here, `s` and `x` can be modified independently.
Creates a vector by copying a slice n times.
This function will panic if the capacity would overflow.
assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);
A panic upon overflow:
/ this will panic at runtime b"0123456789abcdef".repeat(usize::MAX);
Flattens a slice of T into a single value Self::Output.
Self::Output
assert_eq!(["hello", "world"].concat(), "helloworld"); assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);