ByteString in std::bstr - Rust (original) (raw)
#[repr(transparent)]
pub struct ByteString(pub Vec<u8>);🔬This is a nightly-only experimental API. (bstr #134915)
Expand description
A wrapper for Vec<u8> representing a human-readable string that’s conventionally, but not always, UTF-8.
Unlike String, 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.
A ByteString owns its contents and can grow and shrink, like a Vec or String. For a borrowed byte string, see ByteStr.
ByteString implements Deref to &Vec<u8>, so all methods available on &Vec<u8> are available on ByteString. Similarly, ByteString implements DerefMut to &mut Vec<u8>, so you can modify a ByteString using any method available on &mut Vec<u8>.
The Debug and Display implementations for ByteString are the same as those for ByteStr, showing invalid UTF-8 as hex escapes or the Unicode replacement character, respectively.
🔬This is a nightly-only experimental API. (bstr #134915)
1.0.0 · Source
Returns the total number of elements the vector can hold without reallocating.
§Examples
let mut vec: Vec<i32> = Vec::with_capacity(10);
vec.push(42);
assert!(vec.capacity() >= 10);1.0.0 · Source
Reserves capacity for at least additional more elements to be inserted in the given Vec<T>. The collection may reserve more space to speculatively avoid frequent reallocations. After calling reserve, capacity will be greater than or equal to self.len() + additional. Does nothing if capacity is already sufficient.
§Panics
Panics if the new capacity exceeds isize::MAX bytes.
§Examples
let mut vec = vec![1];
vec.reserve(10);
assert!(vec.capacity() >= 11);1.0.0 · Source
Reserves the minimum capacity for at least additional more elements to be inserted in the given Vec<T>. Unlike reserve, this will not deliberately over-allocate to speculatively avoid frequent allocations. After calling reserve_exact, capacity will be greater than or equal toself.len() + additional. Does nothing if the capacity is already sufficient.
Note that the allocator may give the collection more space than it requests. Therefore, capacity can not be relied upon to be precisely minimal. Prefer reserve if future insertions are expected.
§Panics
Panics if the new capacity exceeds isize::MAX bytes.
§Examples
let mut vec = vec![1];
vec.reserve_exact(10);
assert!(vec.capacity() >= 11);1.57.0 · Source
Tries to reserve capacity for at least additional more elements to be inserted in the given Vec<T>. The collection may reserve more space to speculatively avoid frequent reallocations. After calling try_reserve, capacity will be greater than or equal to self.len() + additional if it returnsOk(()). Does nothing if capacity is already sufficient. This method preserves the contents even if an error occurs.
§Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
§Examples
use std::collections::TryReserveError;
fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> {
let mut output = Vec::new();
// Pre-reserve the memory, exiting if we can't
output.try_reserve(data.len())?;
// Now we know this can't OOM in the middle of our complex work
output.extend(data.iter().map(|&val| {
val * 2 + 5 // very complicated
}));
Ok(output)
}1.57.0 · Source
Tries to reserve the minimum capacity for at least additionalelements to be inserted in the given Vec<T>. Unlike try_reserve, this will not deliberately over-allocate to speculatively avoid frequent allocations. After calling try_reserve_exact, capacity will be greater than or equal to self.len() + additional if it returns Ok(()). Does nothing if the capacity is already sufficient.
Note that the allocator may give the collection more space than it requests. Therefore, capacity can not be relied upon to be precisely minimal. Prefer try_reserve if future insertions are expected.
§Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
§Examples
use std::collections::TryReserveError;
fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> {
let mut output = Vec::new();
// Pre-reserve the memory, exiting if we can't
output.try_reserve_exact(data.len())?;
// Now we know this can't OOM in the middle of our complex work
output.extend(data.iter().map(|&val| {
val * 2 + 5 // very complicated
}));
Ok(output)
}1.0.0 · Source
Shrinks the capacity of the vector as much as possible.
The behavior of this method depends on the allocator, which may either shrink the vector in-place or reallocate. The resulting vector might still have some excess capacity, just as is the case for with_capacity. See Allocator::shrink for more details.
§Examples
let mut vec = Vec::with_capacity(10);
vec.extend([1, 2, 3]);
assert!(vec.capacity() >= 10);
vec.shrink_to_fit();
assert!(vec.capacity() >= 3);1.56.0 · Source
Shrinks the capacity of the vector with a lower bound.
The capacity will remain at least as large as both the length and the supplied value.
If the current capacity is less than the lower limit, this is a no-op.
§Examples
let mut vec = Vec::with_capacity(10);
vec.extend([1, 2, 3]);
assert!(vec.capacity() >= 10);
vec.shrink_to(4);
assert!(vec.capacity() >= 4);
vec.shrink_to(0);
assert!(vec.capacity() >= 3);1.0.0 · Source
Shortens the vector, keeping the first len elements and dropping the rest.
If len is greater or equal to the vector’s current length, this has no effect.
The drain method can emulate truncate, but causes the excess elements to be returned instead of dropped.
Note that this method has no effect on the allocated capacity of the vector.
§Examples
Truncating a five element vector to two elements:
let mut vec = vec![1, 2, 3, 4, 5];
vec.truncate(2);
assert_eq!(vec, [1, 2]);No truncation occurs when len is greater than the vector’s current length:
let mut vec = vec![1, 2, 3];
vec.truncate(8);
assert_eq!(vec, [1, 2, 3]);Truncating when len == 0 is equivalent to calling the clearmethod.
let mut vec = vec![1, 2, 3];
vec.truncate(0);
assert_eq!(vec, []);1.7.0 · Source
Extracts a slice containing the entire vector.
Equivalent to &s[..].
§Examples
use std::io::{self, Write};
let buffer = vec![1, 2, 3, 5, 8];
io::sink().write(buffer.as_slice()).unwrap();1.7.0 · Source
Extracts a mutable slice of the entire vector.
Equivalent to &mut s[..].
§Examples
use std::io::{self, Read};
let mut buffer = vec![0; 3];
io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap();1.37.0 · Source
Returns a raw pointer to the vector’s buffer, or a dangling raw pointer valid for zero sized reads if the vector didn’t allocate.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up dangling. Modifying the vector may cause its buffer to be reallocated, which would also make any pointers to it invalid.
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.
This method guarantees that for the purpose of the aliasing model, this method does not materialize a reference to the underlying slice, and thus the returned pointer will remain valid when mixed with other calls to as_ptr, as_mut_ptr, and as_non_null. Note that calling other methods that materialize mutable references to the slice, or mutable references to specific elements you are planning on accessing through this pointer, as well as writing to those elements, may still invalidate this pointer. See the second example below for how this guarantee can be used.
§Examples
let x = vec![1, 2, 4];
let x_ptr = x.as_ptr();
unsafe {
for i in 0..x.len() {
assert_eq!(*x_ptr.add(i), 1 << i);
}
}Due to the aliasing guarantee, the following code is legal:
unsafe {
let mut v = vec![0, 1, 2];
let ptr1 = v.as_ptr();
let _ = ptr1.read();
let ptr2 = v.as_mut_ptr().offset(2);
ptr2.write(2);
// Notably, the write to `ptr2` did *not* invalidate `ptr1`
// because it mutated a different element:
let _ = ptr1.read();
}1.37.0 · Source
Returns a raw mutable pointer to the vector’s buffer, or a dangling raw pointer valid for zero sized reads if the vector didn’t allocate.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up dangling. Modifying the vector may cause its buffer to be reallocated, which would also make any pointers to it invalid.
This method guarantees that for the purpose of the aliasing model, this method does not materialize a reference to the underlying slice, and thus the returned pointer will remain valid when mixed with other calls to as_ptr, as_mut_ptr, and as_non_null. Note that calling other methods that materialize references to the slice, or references to specific elements you are planning on accessing through this pointer, may still invalidate this pointer. See the second example below for how this guarantee can be used.
§Examples
// Allocate vector big enough for 4 elements.
let size = 4;
let mut x: Vec<i32> = Vec::with_capacity(size);
let x_ptr = x.as_mut_ptr();
// Initialize elements via raw pointer writes, then set length.
unsafe {
for i in 0..size {
*x_ptr.add(i) = i as i32;
}
x.set_len(size);
}
assert_eq!(&*x, &[0, 1, 2, 3]);Due to the aliasing guarantee, the following code is legal:
unsafe {
let mut v = vec![0];
let ptr1 = v.as_mut_ptr();
ptr1.write(1);
let ptr2 = v.as_mut_ptr();
ptr2.write(2);
// Notably, the write to `ptr2` did *not* invalidate `ptr1`:
ptr1.write(3);
}🔬This is a nightly-only experimental API. (box_vec_non_null #130364)
Returns a NonNull pointer to the vector’s buffer, or a danglingNonNull pointer valid for zero sized reads if the vector didn’t allocate.
The caller must ensure that the vector outlives the pointer this function returns, or else it will end up dangling. Modifying the vector may cause its buffer to be reallocated, which would also make any pointers to it invalid.
This method guarantees that for the purpose of the aliasing model, this method does not materialize a reference to the underlying slice, and thus the returned pointer will remain valid when mixed with other calls to as_ptr, as_mut_ptr, and as_non_null. Note that calling other methods that materialize references to the slice, or references to specific elements you are planning on accessing through this pointer, may still invalidate this pointer. See the second example below for how this guarantee can be used.
§Examples
#![feature(box_vec_non_null)]
// Allocate vector big enough for 4 elements.
let size = 4;
let mut x: Vec<i32> = Vec::with_capacity(size);
let x_ptr = x.as_non_null();
// Initialize elements via raw pointer writes, then set length.
unsafe {
for i in 0..size {
x_ptr.add(i).write(i as i32);
}
x.set_len(size);
}
assert_eq!(&*x, &[0, 1, 2, 3]);Due to the aliasing guarantee, the following code is legal:
#![feature(box_vec_non_null)]
unsafe {
let mut v = vec![0];
let ptr1 = v.as_non_null();
ptr1.write(1);
let ptr2 = v.as_non_null();
ptr2.write(2);
// Notably, the write to `ptr2` did *not* invalidate `ptr1`:
ptr1.write(3);
}🔬This is a nightly-only experimental API. (allocator_api #32838)
Returns a reference to the underlying allocator.
1.0.0 · Source
Forces the length of the vector to new_len.
This is a low-level operation that maintains none of the normal invariants of the type. Normally changing the length of a vector is done using one of the safe operations instead, such astruncate, resize, extend, or clear.
§Safety
new_lenmust be less than or equal to capacity().- The elements at
old_len..new_lenmust be initialized.
§Examples
See spare_capacity_mut() for an example with safe initialization of capacity elements and use of this method.
set_len() can be useful for situations in which the vector is serving as a buffer for other code, particularly over FFI:
pub fn get_dictionary(&self) -> Option<Vec<u8>> {
// Per the FFI method's docs, "32768 bytes is always enough".
let mut dict = Vec::with_capacity(32_768);
let mut dict_length = 0;
// SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that:
// 1. `dict_length` elements were initialized.
// 2. `dict_length` <= the capacity (32_768)
// which makes `set_len` safe to call.
unsafe {
// Make the FFI call...
let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length);
if r == Z_OK {
// ...and update the length to what was initialized.
dict.set_len(dict_length);
Some(dict)
} else {
None
}
}
}While the following example is sound, there is a memory leak since the inner vectors were not freed prior to the set_len call:
let mut vec = vec![vec![1, 0, 0],
vec![0, 1, 0],
vec![0, 0, 1]];
// SAFETY:
// 1. `old_len..0` is empty so no elements need to be initialized.
// 2. `0 <= capacity` always holds whatever `capacity` is.
unsafe {
vec.set_len(0);
}Normally, here, one would use clear instead to correctly drop the contents and thus not leak memory.
1.0.0 · Source
Removes an element from the vector and returns it.
The removed element is replaced by the last element of the vector.
This does not preserve ordering of the remaining elements, but is O(1). If you need to preserve the element order, use remove instead.
§Panics
Panics if index is out of bounds.
§Examples
let mut v = vec!["foo", "bar", "baz", "qux"];
assert_eq!(v.swap_remove(1), "bar");
assert_eq!(v, ["foo", "qux", "baz"]);
assert_eq!(v.swap_remove(0), "foo");
assert_eq!(v, ["baz", "qux"]);1.0.0 · Source
Inserts an element at position index within the vector, shifting all elements after it to the right.
§Panics
Panics if index > len.
§Examples
let mut vec = vec!['a', 'b', 'c'];
vec.insert(1, 'd');
assert_eq!(vec, ['a', 'd', 'b', 'c']);
vec.insert(4, 'e');
assert_eq!(vec, ['a', 'd', 'b', 'c', 'e']);§Time complexity
Takes O(Vec::len) time. All items after the insertion index must be shifted to the right. In the worst case, all elements are shifted when the insertion index is 0.
1.0.0 · Source
Removes and returns the element at position index within the vector, shifting all elements after it to the left.
Note: Because this shifts over the remaining elements, it has a worst-case performance of O(n). If you don’t need the order of elements to be preserved, use swap_remove instead. If you’d like to remove elements from the beginning of the Vec, consider usingVecDeque::pop_front instead.
§Panics
Panics if index is out of bounds.
§Examples
let mut v = vec!['a', 'b', 'c'];
assert_eq!(v.remove(1), 'b');
assert_eq!(v, ['a', 'c']);1.0.0 · Source
Retains only the elements specified by the predicate.
In other words, remove all elements e for which f(&e) returns false. This method operates in place, visiting each element exactly once in the original order, and preserves the order of the retained elements.
§Examples
let mut vec = vec![1, 2, 3, 4];
vec.retain(|&x| x % 2 == 0);
assert_eq!(vec, [2, 4]);Because the elements are visited exactly once in the original order, external state may be used to decide which elements to keep.
let mut vec = vec![1, 2, 3, 4, 5];
let keep = [false, true, true, false, true];
let mut iter = keep.iter();
vec.retain(|_| *iter.next().unwrap());
assert_eq!(vec, [2, 3, 5]);1.61.0 · Source
Retains only the elements specified by the predicate, passing a mutable reference to it.
In other words, remove all elements e such that f(&mut e) returns false. This method operates in place, visiting each element exactly once in the original order, and preserves the order of the retained elements.
§Examples
let mut vec = vec![1, 2, 3, 4];
vec.retain_mut(|x| if *x <= 3 {
*x += 1;
true
} else {
false
});
assert_eq!(vec, [2, 3, 4]);1.16.0 · Source
Removes all but the first of consecutive elements in the vector that resolve to the same key.
If the vector is sorted, this removes all duplicates.
§Examples
let mut vec = vec![10, 20, 21, 30, 20];
vec.dedup_by_key(|i| *i / 10);
assert_eq!(vec, [10, 20, 30, 20]);1.16.0 · Source
Removes all but the first of consecutive elements in the vector satisfying a given equality relation.
The same_bucket function is passed references to two elements from the vector 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 removed.
If the vector is sorted, this removes all duplicates.
§Examples
let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"];
vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b));
assert_eq!(vec, ["foo", "bar", "baz", "bar"]);1.0.0 · Source
Appends an element to the back of a collection.
§Panics
Panics if the new capacity exceeds isize::MAX bytes.
§Examples
let mut vec = vec![1, 2];
vec.push(3);
assert_eq!(vec, [1, 2, 3]);§Time complexity
Takes amortized O(1) time. If the vector’s length would exceed its capacity after the push, O(capacity) time is taken to copy the vector’s elements to a larger allocation. This expensive operation is offset by the capacity O(1) insertions it allows.
🔬This is a nightly-only experimental API. (vec_push_within_capacity #100486)
Appends an element if there is sufficient spare capacity, otherwise an error is returned with the element.
Unlike push this method will not reallocate when there’s insufficient capacity. The caller should use reserve or try_reserve to ensure that there is enough capacity.
§Examples
A manual, panic-free alternative to FromIterator:
#![feature(vec_push_within_capacity)]
use std::collections::TryReserveError;
fn from_iter_fallible<T>(iter: impl Iterator<Item=T>) -> Result<Vec<T>, TryReserveError> {
let mut vec = Vec::new();
for value in iter {
if let Err(value) = vec.push_within_capacity(value) {
vec.try_reserve(1)?;
// this cannot fail, the previous line either returned or added at least 1 free slot
let _ = vec.push_within_capacity(value);
}
}
Ok(vec)
}
assert_eq!(from_iter_fallible(0..100), Ok(Vec::from_iter(0..100)));§Time complexity
Takes O(1) time.
1.0.0 · Source
Removes the last element from a vector and returns it, or None if it is empty.
If you’d like to pop the first element, consider usingVecDeque::pop_front instead.
§Examples
let mut vec = vec![1, 2, 3];
assert_eq!(vec.pop(), Some(3));
assert_eq!(vec, [1, 2]);§Time complexity
Takes O(1) time.
1.86.0 · Source
Removes and returns the last element from a vector if the predicate returns true, or None if the predicate returns false or the vector is empty (the predicate will not be called in that case).
§Examples
let mut vec = vec![1, 2, 3, 4];
let pred = |x: &mut i32| *x % 2 == 0;
assert_eq!(vec.pop_if(pred), Some(4));
assert_eq!(vec, [1, 2, 3]);
assert_eq!(vec.pop_if(pred), None);1.4.0 · Source
Moves all the elements of other into self, leaving other empty.
§Panics
Panics if the new capacity exceeds isize::MAX bytes.
§Examples
let mut vec = vec![1, 2, 3];
let mut vec2 = vec![4, 5, 6];
vec.append(&mut vec2);
assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
assert_eq!(vec2, []);1.6.0 · Source
Removes the subslice indicated by the given range from the vector, returning a double-ended iterator over the removed subslice.
If the iterator is dropped before being fully consumed, it drops the remaining removed elements.
The returned iterator keeps a mutable borrow on the vector to optimize its implementation.
§Panics
Panics if the starting point is greater than the end point or if the end point is greater than the length of the vector.
§Leaking
If the returned iterator goes out of scope without being dropped (due tomem::forget, for example), the vector may have lost and leaked elements arbitrarily, including elements outside the range.
§Examples
let mut v = vec![1, 2, 3];
let u: Vec<_> = v.drain(1..).collect();
assert_eq!(v, &[1]);
assert_eq!(u, &[2, 3]);
// A full range clears the vector, like `clear()` does
v.drain(..);
assert_eq!(v, &[]);1.0.0 · Source
Clears the vector, removing all values.
Note that this method has no effect on the allocated capacity of the vector.
§Examples
let mut v = vec![1, 2, 3];
v.clear();
assert!(v.is_empty());1.0.0 · Source
Returns the number of elements in the vector, also referred to as its ‘length’.
§Examples
let a = vec![1, 2, 3];
assert_eq!(a.len(), 3);1.0.0 · Source
Returns true if the vector contains no elements.
§Examples
let mut v = Vec::new();
assert!(v.is_empty());
v.push(1);
assert!(!v.is_empty());1.4.0 · Source
Splits the collection into two at the given index.
Returns a newly allocated vector containing the elements in the range[at, len). After the call, the original vector will be left containing the elements [0, at) with its previous capacity unchanged.
- If you want to take ownership of the entire contents and capacity of the vector, see mem::take or mem::replace.
- If you don’t need the returned vector at all, see Vec::truncate.
- If you want to take ownership of an arbitrary subslice, or you don’t necessarily want to store the removed items in a vector, see Vec::drain.
§Panics
Panics if at > len.
§Examples
let mut vec = vec!['a', 'b', 'c'];
let vec2 = vec.split_off(1);
assert_eq!(vec, ['a']);
assert_eq!(vec2, ['b', 'c']);1.33.0 · Source
Resizes the Vec in-place so that len is equal to new_len.
If new_len is greater than len, the Vec is extended by the difference, with each additional slot filled with the result of calling the closure f. The return values from f will end up in the Vec in the order they have been generated.
If new_len is less than len, the Vec is simply truncated.
This method uses a closure to create new values on every push. If you’d rather Clone a given value, use Vec::resize. If you want to use the Default trait to generate values, you can pass Default::default as the second argument.
§Examples
let mut vec = vec![1, 2, 3];
vec.resize_with(5, Default::default);
assert_eq!(vec, [1, 2, 3, 0, 0]);
let mut vec = vec![];
let mut p = 1;
vec.resize_with(4, || { p *= 2; p });
assert_eq!(vec, [2, 4, 8, 16]);1.60.0 · Source
Returns the remaining spare capacity of the vector as a slice ofMaybeUninit<T>.
The returned slice can be used to fill the vector with data (e.g. by reading from a file) before marking the data as initialized using theset_len method.
§Examples
// Allocate vector big enough for 10 elements.
let mut v = Vec::with_capacity(10);
// Fill in the first 3 elements.
let uninit = v.spare_capacity_mut();
uninit[0].write(0);
uninit[1].write(1);
uninit[2].write(2);
// Mark the first 3 elements of the vector as being initialized.
unsafe {
v.set_len(3);
}
assert_eq!(&v, &[0, 1, 2]);🔬This is a nightly-only experimental API. (vec_split_at_spare #81944)
Returns vector content as a slice of T, along with the remaining spare capacity of the vector as a slice of MaybeUninit<T>.
The returned spare capacity slice can be used to fill the vector with data (e.g. by reading from a file) before marking the data as initialized using the set_len method.
Note that this is a low-level API, which should be used with care for optimization purposes. If you need to append data to a Vecyou can use push, extend, extend_from_slice,extend_from_within, insert, append, resize orresize_with, depending on your exact needs.
§Examples
#![feature(vec_split_at_spare)]
let mut v = vec![1, 1, 2];
// Reserve additional space big enough for 10 elements.
v.reserve(10);
let (init, uninit) = v.split_at_spare_mut();
let sum = init.iter().copied().sum::<u32>();
// Fill in the next 4 elements.
uninit[0].write(sum);
uninit[1].write(sum * 2);
uninit[2].write(sum * 3);
uninit[3].write(sum * 4);
// Mark the 4 elements of the vector as being initialized.
unsafe {
let len = v.len();
v.set_len(len + 4);
}
assert_eq!(&v, &[1, 1, 2, 4, 8, 12, 16]);1.5.0 · Source
Resizes the Vec in-place so that len is equal to new_len.
If new_len is greater than len, the Vec is extended by the difference, with each additional slot filled with value. If new_len is less than len, the Vec is simply truncated.
This method requires T to implement Clone, in order to be able to clone the passed value. If you need more flexibility (or want to rely on Default instead ofClone), use Vec::resize_with. If you only need to resize to a smaller size, use Vec::truncate.
§Examples
let mut vec = vec!["hello"];
vec.resize(3, "world");
assert_eq!(vec, ["hello", "world", "world"]);
let mut vec = vec!['a', 'b', 'c', 'd'];
vec.resize(2, '_');
assert_eq!(vec, ['a', 'b']);1.6.0 · Source
Clones and appends all elements in a slice to the Vec.
Iterates over the slice other, clones each element, and then appends it to this Vec. The other slice is traversed in-order.
Note that this function is the same as extend, except that it also works with slice elements that are Clone but not Copy. If Rust gets specialization this function may be deprecated.
§Examples
let mut vec = vec![1];
vec.extend_from_slice(&[2, 3, 4]);
assert_eq!(vec, [1, 2, 3, 4]);1.53.0 · Source
Given a range src, clones a slice of elements in that range and appends it to the end.
src must be a range that can form a valid subslice of the Vec.
§Panics
Panics if starting index is greater than the end index or if the index is greater than the length of the vector.
§Examples
let mut characters = vec!['a', 'b', 'c', 'd', 'e'];
characters.extend_from_within(2..);
assert_eq!(characters, ['a', 'b', 'c', 'd', 'e', 'c', 'd', 'e']);
let mut numbers = vec![0, 1, 2, 3, 4];
numbers.extend_from_within(..2);
assert_eq!(numbers, [0, 1, 2, 3, 4, 0, 1]);
let mut strings = vec![String::from("hello"), String::from("world"), String::from("!")];
strings.extend_from_within(1..=2);
assert_eq!(strings, ["hello", "world", "!", "world", "!"]);1.0.0 · Source
Removes consecutive repeated elements in the vector according to thePartialEq trait implementation.
If the vector is sorted, this removes all duplicates.
§Examples
let mut vec = vec![1, 2, 2, 3, 2];
vec.dedup();
assert_eq!(vec, [1, 2, 3, 2]);1.21.0 · Source
Creates a splicing iterator that replaces the specified range in the vector with the given replace_with iterator and yields the removed items.replace_with does not need to be the same length as range.
range is removed even if the Splice iterator is not consumed before it is dropped.
It is unspecified how many elements are removed from the vector if the Splice value is leaked.
The input iterator replace_with is only consumed when the Splice value is dropped.
This is optimal if:
- The tail (elements in the vector after
range) is empty, - or
replace_withyields fewer or equal elements thanrange’s length - or the lower bound of its
size_hint()is exact.
Otherwise, a temporary vector is allocated and the tail is moved twice.
§Panics
Panics if the starting point is greater than the end point or if the end point is greater than the length of the vector.
§Examples
let mut v = vec![1, 2, 3, 4];
let new = [7, 8, 9];
let u: Vec<_> = v.splice(1..3, new).collect();
assert_eq!(v, [1, 7, 8, 9, 4]);
assert_eq!(u, [2, 3]);Using splice to insert new items into a vector efficiently at a specific position indicated by an empty range:
let mut v = vec![1, 5];
let new = [2, 3, 4];
v.splice(1..1, new);
assert_eq!(v, [1, 2, 3, 4, 5]);🔬This is a nightly-only experimental API. (extract_if #43244)
Creates an iterator which uses a closure to determine if element in the range should be removed.
If the closure returns true, then the element is removed and yielded. If the closure returns false, the element will remain in the vector and will not be yielded by the iterator.
Only elements that fall in the provided range are considered for extraction, but any elements after the range will still have to be moved if any element has been extracted.
If the returned ExtractIf is not exhausted, e.g. because it is dropped without iterating or the iteration short-circuits, then the remaining elements will be retained. Use retain with a negated predicate if you do not need the returned iterator.
Using this method is equivalent to the following code:
let mut i = range.start;
while i < min(vec.len(), range.end) {
if some_predicate(&mut vec[i]) {
let val = vec.remove(i);
// your code here
} else {
i += 1;
}
}
But extract_if is easier to use. extract_if is also more efficient, because it can backshift the elements of the array in bulk.
Note that extract_if also lets you mutate the elements passed to the filter closure, regardless of whether you choose to keep or remove them.
§Panics
If range is out of bounds.
§Examples
Splitting an array into evens and odds, reusing the original allocation:
#![feature(extract_if)]
let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
let evens = numbers.extract_if(.., |x| *x % 2 == 0).collect::<Vec<_>>();
let odds = numbers;
assert_eq!(evens, vec![2, 4, 6, 8, 14]);
assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);Using the range argument to only process a part of the vector:
#![feature(extract_if)]
let mut items = vec![0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 2, 1, 2];
let ones = items.extract_if(7.., |x| *x == 1).collect::<Vec<_>>();
assert_eq!(items, vec![0, 0, 0, 0, 0, 0, 0, 2, 2, 2]);
assert_eq!(ones.len(), 3);🔬This is a nightly-only experimental API. (maybe_uninit_write_slice #79995)
Copies the elements from src to self, returning a mutable reference to the now initialized contents of self.
If T does not implement Copy, use write_clone_of_slice instead.
This is similar to slice::copy_from_slice.
§Panics
This function will panic if the two slices have different lengths.
§Examples
#![feature(maybe_uninit_write_slice)]
use std::mem::MaybeUninit;
let mut dst = [MaybeUninit::uninit(); 32];
let src = [0; 32];
let init = dst.write_copy_of_slice(&src);
assert_eq!(init, src);#![feature(maybe_uninit_write_slice)]
let mut vec = Vec::with_capacity(32);
let src = [0; 16];
vec.spare_capacity_mut()[..src.len()].write_copy_of_slice(&src);
// SAFETY: we have just copied all the elements of len into the spare capacity
// the first src.len() elements of the vec are valid now.
unsafe {
vec.set_len(src.len());
}
assert_eq!(vec, src);🔬This is a nightly-only experimental API. (maybe_uninit_write_slice #79995)
Clones the elements from src to self, returning a mutable reference to the now initialized contents of self. Any already initialized elements will not be dropped.
If T implements Copy, use write_copy_of_slice instead.
This is similar to slice::clone_from_slice but does not drop existing elements.
§Panics
This function will panic if the two slices have different lengths, or if the implementation of Clone panics.
If there is a panic, the already cloned elements will be dropped.
§Examples
#![feature(maybe_uninit_write_slice)]
use std::mem::MaybeUninit;
let mut dst = [const { MaybeUninit::uninit() }; 5];
let src = ["wibbly", "wobbly", "timey", "wimey", "stuff"].map(|s| s.to_string());
let init = dst.write_clone_of_slice(&src);
assert_eq!(init, src);
#![feature(maybe_uninit_write_slice)]
let mut vec = Vec::with_capacity(32);
let src = ["rust", "is", "a", "pretty", "cool", "language"].map(|s| s.to_string());
vec.spare_capacity_mut()[..src.len()].write_clone_of_slice(&src);
// SAFETY: we have just cloned all the elements of len into the spare capacity
// the first src.len() elements of the vec are valid now.
unsafe {
vec.set_len(src.len());
}
assert_eq!(vec, src);🔬This is a nightly-only experimental API. (maybe_uninit_as_bytes #93092)
Returns the contents of this MaybeUninit as a slice of potentially uninitialized bytes.
Note that even if the contents of a MaybeUninit have been initialized, the value may still contain padding bytes which are left uninitialized.
§Examples
#![feature(maybe_uninit_as_bytes, maybe_uninit_write_slice, maybe_uninit_slice)]
use std::mem::MaybeUninit;
let uninit = [MaybeUninit::new(0x1234u16), MaybeUninit::new(0x5678u16)];
let uninit_bytes = uninit.as_bytes();
let bytes = unsafe { uninit_bytes.assume_init_ref() };
let val1 = u16::from_ne_bytes(bytes[0..2].try_into().unwrap());
let val2 = u16::from_ne_bytes(bytes[2..4].try_into().unwrap());
assert_eq!(&[val1, val2], &[0x1234u16, 0x5678u16]);🔬This is a nightly-only experimental API. (maybe_uninit_as_bytes #93092)
Returns the contents of this MaybeUninit slice as a mutable slice of potentially uninitialized bytes.
Note that even if the contents of a MaybeUninit have been initialized, the value may still contain padding bytes which are left uninitialized.
§Examples
#![feature(maybe_uninit_as_bytes, maybe_uninit_write_slice, maybe_uninit_slice)]
use std::mem::MaybeUninit;
let mut uninit = [MaybeUninit::<u16>::uninit(), MaybeUninit::<u16>::uninit()];
let uninit_bytes = MaybeUninit::slice_as_bytes_mut(&mut uninit);
uninit_bytes.write_copy_of_slice(&[0x12, 0x34, 0x56, 0x78]);
let vals = unsafe { uninit.assume_init_ref() };
if cfg!(target_endian = "little") {
assert_eq!(vals, &[0x3412u16, 0x7856u16]);
} else {
assert_eq!(vals, &[0x1234u16, 0x5678u16]);
}🔬This is a nightly-only experimental API. (maybe_uninit_slice #63569)
Drops the contained values in place.
§Safety
It is up to the caller to guarantee that every MaybeUninit<T> in the slice really is in an initialized state. Calling this when the content is not yet fully initialized causes undefined behavior.
On top of that, all additional invariants of the type T must be satisfied, as the Drop implementation of T (or its members) may rely on this. For example, setting a Vec<T> to an invalid but non-null address makes it initialized (under the current implementation; this does not constitute a stable guarantee), because the only requirement the compiler knows about it is that the data pointer must be non-null. Dropping such a Vec<T> however will cause undefined behaviour.
🔬This is a nightly-only experimental API. (maybe_uninit_slice #63569)
Gets a shared reference to the contained value.
§Safety
Calling this when the content is not yet fully initialized causes undefined behavior: it is up to the caller to guarantee that every MaybeUninit<T> in the slice really is in an initialized state.
🔬This is a nightly-only experimental API. (maybe_uninit_slice #63569)
Gets a mutable (unique) reference to the contained value.
§Safety
Calling this when the content is not yet fully initialized causes undefined behavior: it is up to the caller to guarantee that every MaybeUninit<T> in the slice really is in an initialized state. For instance, .assume_init_mut() cannot be used to initialize a MaybeUninit slice.
🔬This is a nightly-only experimental API. (ascii_char #110998)
Views this slice of ASCII characters as a UTF-8 str.
🔬This is a nightly-only experimental API. (ascii_char #110998)
Views this slice of ASCII characters as a slice of u8 bytes.
1.23.0 · Source
Checks if all bytes in this slice are within the ASCII range.
🔬This is a nightly-only experimental API. (ascii_char #110998)
🔬This is a nightly-only experimental API. (ascii_char #110998)
Converts this slice of bytes into a slice of ASCII characters, without checking whether they’re valid.
§Safety
Every byte in the slice must be in 0..=127, or else this is UB.
1.23.0 · Source
Checks that two slices are an ASCII case-insensitive match.
Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.
1.23.0 · Source
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, useto_ascii_uppercase.
1.23.0 · Source
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, useto_ascii_lowercase.
1.60.0 · Source
Returns an iterator that produces an escaped version of this slice, treating it as an ASCII string.
§Examples
let s = b"0\t\r\n'\"\\\x9d";
let escaped = s.escape_ascii().to_string();
assert_eq!(escaped, "0\\t\\r\\n\\'\\\"\\\\\\x9d");1.80.0 · Source
Returns a byte slice with leading ASCII whitespace bytes removed.
‘Whitespace’ refers to the definition used byu8::is_ascii_whitespace.
§Examples
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"");1.80.0 · Source
Returns a byte slice with trailing ASCII whitespace bytes removed.
‘Whitespace’ refers to the definition used byu8::is_ascii_whitespace.
§Examples
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"");1.80.0 · Source
Returns a byte slice with leading and trailing ASCII whitespace bytes removed.
‘Whitespace’ refers to the definition used byu8::is_ascii_whitespace.
§Examples
assert_eq!(b"\r hello world\n ".trim_ascii(), b"hello world");
assert_eq!(b" ".trim_ascii(), b"");
assert_eq!(b"".trim_ascii(), b"");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++.
🔬This is a nightly-only experimental API. (slice_as_array #133508)
Gets a reference to the underlying array.
If N is not exactly equal to the length of self, then this method returns None.
🔬This is a nightly-only experimental API. (slice_as_array #133508)
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 #88539)
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.
§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.
§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.
§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.
§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]);🔬This is a nightly-only experimental API. (slice_as_chunks #74985)
Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.
§Safety
This may only be called when
- The slice splits exactly into
N-element chunks (akaself.len() % N == 0). N != 0.
§Examples
#![feature(slice_as_chunks)]
let slice: &[char] = &['l', 'o', 'r', 'e', 'm', '!'];
let chunks: &[[char; 1]] =
// SAFETY: 1-element chunks never have remainder
unsafe { slice.as_chunks_unchecked() };
assert_eq!(chunks, &[['l'], ['o'], ['r'], ['e'], ['m'], ['!']]);
let chunks: &[[char; 3]] =
// SAFETY: The slice length (6) is a multiple of 3
unsafe { slice.as_chunks_unchecked() };
assert_eq!(chunks, &[['l', 'o', 'r'], ['e', 'm', '!']]);
// These would be unsound:
// let chunks: &[[_; 5]] = slice.as_chunks_unchecked() // The slice length is not a multiple of 5
// let chunks: &[[_; 0]] = slice.as_chunks_unchecked() // Zero-length chunks are never allowed🔬This is a nightly-only experimental API. (slice_as_chunks #74985)
Splits the slice into a slice of N-element arrays, starting at the beginning of the slice, and a remainder slice with length strictly less than N.
§Panics
Panics if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(slice_as_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let (chunks, remainder) = slice.as_chunks();
assert_eq!(chunks, &[['l', 'o'], ['r', 'e']]);
assert_eq!(remainder, &['m']);If you expect the slice to be an exact multiple, you can combinelet-else with an empty slice pattern:
#![feature(slice_as_chunks)]
let slice = ['R', 'u', 's', 't'];
let (chunks, []) = slice.as_chunks::<2>() else {
panic!("slice didn't have even length")
};
assert_eq!(chunks, &[['R', 'u'], ['s', 't']]);🔬This is a nightly-only experimental API. (slice_as_chunks #74985)
Splits the slice into a slice of N-element arrays, starting at the end of the slice, and a remainder slice with length strictly less than N.
§Panics
Panics if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(slice_as_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let (remainder, chunks) = slice.as_rchunks();
assert_eq!(remainder, &['l']);
assert_eq!(chunks, &[['o', 'r'], ['e', 'm']]);🔬This is a nightly-only experimental API. (array_chunks #74985)
Returns an iterator over N elements of the slice at a time, starting at the beginning of the slice.
The chunks are array references and do not overlap. If N does not divide the length of the slice, then the last up to N-1 elements will be omitted and can be retrieved from the remainder function of the iterator.
This method is the const generic equivalent of chunks_exact.
§Panics
Panics if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(array_chunks)]
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.array_chunks();
assert_eq!(iter.next().unwrap(), &['l', 'o']);
assert_eq!(iter.next().unwrap(), &['r', 'e']);
assert!(iter.next().is_none());
assert_eq!(iter.remainder(), &['m']);🔬This is a nightly-only experimental API. (slice_as_chunks #74985)
Splits the slice into a slice of N-element arrays, assuming that there’s no remainder.
§Safety
This may only be called when
- The slice splits exactly into
N-element chunks (akaself.len() % N == 0). N != 0.
§Examples
#![feature(slice_as_chunks)]
let slice: &mut [char] = &mut ['l', 'o', 'r', 'e', 'm', '!'];
let chunks: &mut [[char; 1]] =
// SAFETY: 1-element chunks never have remainder
unsafe { slice.as_chunks_unchecked_mut() };
chunks[0] = ['L'];
assert_eq!(chunks, &[['L'], ['o'], ['r'], ['e'], ['m'], ['!']]);
let chunks: &mut [[char; 3]] =
// SAFETY: The slice length (6) is a multiple of 3
unsafe { slice.as_chunks_unchecked_mut() };
chunks[1] = ['a', 'x', '?'];
assert_eq!(slice, &['L', 'o', 'r', 'a', 'x', '?']);
// These would be unsound:
// let chunks: &[[_; 5]] = slice.as_chunks_unchecked_mut() // The slice length is not a multiple of 5
// let chunks: &[[_; 0]] = slice.as_chunks_unchecked_mut() // Zero-length chunks are never allowed🔬This is a nightly-only experimental API. (slice_as_chunks #74985)
Splits the slice into a slice of N-element arrays, starting at the beginning of the slice, and a remainder slice with length strictly less than N.
§Panics
Panics if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(slice_as_chunks)]
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;
let (chunks, remainder) = v.as_chunks_mut();
remainder[0] = 9;
for chunk in chunks {
*chunk = [count; 2];
count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 9]);🔬This is a nightly-only experimental API. (slice_as_chunks #74985)
Splits the slice into a slice of N-element arrays, starting at the end of the slice, and a remainder slice with length strictly less than N.
§Panics
Panics if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(slice_as_chunks)]
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;
let (remainder, chunks) = v.as_rchunks_mut();
remainder[0] = 9;
for chunk in chunks {
*chunk = [count; 2];
count += 1;
}
assert_eq!(v, &[9, 1, 1, 2, 2]);🔬This is a nightly-only experimental API. (array_chunks #74985)
Returns an iterator over N elements of the slice at a time, starting at the beginning of the slice.
The chunks are mutable array references and do not overlap. If N does not divide the length of the slice, then the last up to N-1 elements will be omitted and can be retrieved from the into_remainder function of the iterator.
This method is the const generic equivalent of chunks_exact_mut.
§Panics
Panics if N is zero. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(array_chunks)]
let v = &mut [0, 0, 0, 0, 0];
let mut count = 1;
for chunk in v.array_chunks_mut() {
*chunk = [count; 2];
count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 0]);🔬This is a nightly-only experimental API. (array_windows #75027)
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. This check will most probably get changed to a compile time error before this method gets stabilized.
§Examples
#![feature(array_windows)]
let slice = [0, 1, 2, 3];
let mut iter = slice.array_windows();
assert_eq!(iter.next().unwrap(), &[0, 1]);
assert_eq!(iter.next().unwrap(), &[1, 2]);
assert_eq!(iter.next().unwrap(), &[2, 3]);
assert!(iter.next().is_none());1.31.0 · Source
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.
§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.
§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.
§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.
§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 #112811)
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 #112811)
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);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 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 resulting order of elements in the slice is unspecified. 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.
§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 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 resulting order of elements in the slice is unspecified. 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.
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 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 compare does not implement a total order.
§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 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 resulting order of elements in the slice is unspecified. 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.
§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 #54279)
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 #54279)
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 #54279)
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 #86656)
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 #86656)
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]);🔬This is a nightly-only experimental API. (slice_take #62280)
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:
#![feature(slice_take)]
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 the last two elements of a slice:
#![feature(slice_take)]
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:
#![feature(slice_take)]
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));🔬This is a nightly-only experimental API. (slice_take #62280)
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:
#![feature(slice_take)]
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']);Taking the last two elements of a slice:
#![feature(slice_take)]
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:
#![feature(slice_take)]
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));🔬This is a nightly-only experimental API. (slice_take #62280)
Removes the first element of the slice and returns a reference to it.
Returns None if the slice is empty.
§Examples
#![feature(slice_take)]
let mut slice: &[_] = &['a', 'b', 'c'];
let first = slice.split_off_first().unwrap();
assert_eq!(slice, &['b', 'c']);
assert_eq!(first, &'a');🔬This is a nightly-only experimental API. (slice_take #62280)
Removes the first element of the slice and returns a mutable reference to it.
Returns None if the slice is empty.
§Examples
#![feature(slice_take)]
let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
let first = slice.split_off_first_mut().unwrap();
*first = 'd';
assert_eq!(slice, &['b', 'c']);
assert_eq!(first, &'d');🔬This is a nightly-only experimental API. (slice_take #62280)
Removes the last element of the slice and returns a reference to it.
Returns None if the slice is empty.
§Examples
#![feature(slice_take)]
let mut slice: &[_] = &['a', 'b', 'c'];
let last = slice.split_off_last().unwrap();
assert_eq!(slice, &['a', 'b']);
assert_eq!(last, &'c');🔬This is a nightly-only experimental API. (slice_take #62280)
Removes the last element of the slice and returns a mutable reference to it.
Returns None if the slice is empty.
§Examples
#![feature(slice_take)]
let mut slice: &mut [_] = &mut ['a', 'b', 'c'];
let last = slice.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 #126769)
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 #126769)
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));1.80.0 · Source
Takes a &[[T; N]], and flattens it to a &[T].
§Panics
This panics if the length of the resulting slice would overflow a usize.
This is only possible when flattening a slice of arrays of zero-sized types, and thus tends to be irrelevant in practice. Ifsize_of::<T>() > 0, this will never panic.
§Examples
assert_eq!([[1, 2, 3], [4, 5, 6]].as_flattened(), &[1, 2, 3, 4, 5, 6]);
assert_eq!(
[[1, 2, 3], [4, 5, 6]].as_flattened(),
[[1, 2], [3, 4], [5, 6]].as_flattened(),
);
let slice_of_empty_arrays: &[[i32; 0]] = &[[], [], [], [], []];
assert!(slice_of_empty_arrays.as_flattened().is_empty());
let empty_slice_of_arrays: &[[u32; 10]] = &[];
assert!(empty_slice_of_arrays.as_flattened().is_empty());1.80.0 · Source
Takes a &mut [[T; N]], and flattens it to a &mut [T].
§Panics
This panics if the length of the resulting slice would overflow a usize.
This is only possible when flattening a slice of arrays of zero-sized types, and thus tends to be irrelevant in practice. Ifsize_of::<T>() > 0, this will never panic.
§Examples
fn add_5_to_all(slice: &mut [i32]) {
for i in slice {
*i += 5;
}
}
let mut array = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
add_5_to_all(array.as_flattened_mut());
assert_eq!(array, [[6, 7, 8], [9, 10, 11], [12, 13, 14]]);🔬This is a nightly-only experimental API. (sort_floats #93396)
Sorts the slice of floats.
This sort is in-place (i.e. does not allocate), O(n * log(n)) worst-case, and uses the ordering defined by f32::total_cmp.
§Current implementation
This uses the same sorting algorithm as sort_unstable_by.
§Examples
#![feature(sort_floats)]
let mut v = [2.6, -5e-8, f32::NAN, 8.29, f32::INFINITY, -1.0, 0.0, -f32::INFINITY, -0.0];
v.sort_floats();
let sorted = [-f32::INFINITY, -1.0, -5e-8, -0.0, 0.0, 2.6, 8.29, f32::INFINITY, f32::NAN];
assert_eq!(&v[..8], &sorted[..8]);
assert!(v[8].is_nan());🔬This is a nightly-only experimental API. (sort_floats #93396)
Sorts the slice of floats.
This sort is in-place (i.e. does not allocate), O(n * log(n)) worst-case, and uses the ordering defined by f64::total_cmp.
§Current implementation
This uses the same sorting algorithm as sort_unstable_by.
§Examples
#![feature(sort_floats)]
let mut v = [2.6, -5e-8, f64::NAN, 8.29, f64::INFINITY, -1.0, 0.0, -f64::INFINITY, -0.0];
v.sort_floats();
let sorted = [-f64::INFINITY, -1.0, -5e-8, -0.0, 0.0, 2.6, 8.29, f64::INFINITY, f64::NAN];
assert_eq!(&v[..8], &sorted[..8]);
assert!(v[8].is_nan());1.79.0 · Source
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.
§Examples
This function formats arbitrary but mostly-UTF-8 bytes into Rust source code in the form of a C-string literal (c"...").
use std::fmt::Write as _;
pub fn cstr_literal(bytes: &[u8]) -> String {
let mut repr = String::new();
repr.push_str("c\"");
for chunk in bytes.utf8_chunks() {
for ch in chunk.valid().chars() {
// Escapes \0, \t, \r, \n, \\, \', \", and uses \u{...} for non-printable characters.
write!(repr, "{}", ch.escape_debug()).unwrap();
}
for byte in chunk.invalid() {
write!(repr, "\\x{:02X}", byte).unwrap();
}
}
repr.push('"');
repr
}
fn main() {
let lit = cstr_literal(b"\xferris the \xf0\x9f\xa6\x80\x07");
let expected = stringify!(c"\xFErris the 🦀\u{7}");
assert_eq!(lit, expected);
}1.0.0 · Source
Sorts the slice, 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 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 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 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 #32838)
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
Basic usage:
assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);A panic upon overflow:
// this will panic at runtime
b"0123456789abcdef".repeat(usize::MAX);1.0.0 · Source
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]);1.23.0 · Source
Returns a vector containing a copy of this slice where each byte is mapped to its ASCII upper case equivalent.
ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.
To uppercase the value in-place, use make_ascii_uppercase.
1.23.0 · Source
Returns a vector containing a copy of this slice where each byte is mapped to its ASCII lower case equivalent.
ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.
To lowercase the value in-place, use make_ascii_lowercase.
Converts this type into a mutable reference of the (usually inferred) input type.
Converts this type into a mutable reference of the (usually inferred) input type.
Converts this type into a shared reference of the (usually inferred) input type.
Converts this type into a shared reference of the (usually inferred) input type.
The resulting type after dereferencing.
Dereferences the value.
Mutably dereferences the value.
Converts to this type from the input type.
Converts to this type from the input type.
Converts to this type from the input type.
Converts to this type from the input type.
The associated error which can be returned from parsing.
Parses a string s to return a value of this type. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
The returned type after indexing.
Performs the indexing (container[index]) operation. Read more
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.