Struct smallvec::SmallVec

pub struct SmallVec<A: Array> { /* fields omitted */ }

A Vec-like container that can store a small number of elements inline.

SmallVec acts like a vector, but can store a limited amount of data inline within the Smallvec struct rather than in a separate allocation. If the data exceeds this limit, the SmallVec will "spill" its data onto the heap, allocating a new buffer to hold it.

The amount of data that a SmallVec can store inline depends on its backing store. The backing store can be any type that implements the Array trait; usually it is a small fixed-sized array. For example a SmallVec<[u64; 8]> can hold up to eight 64-bit integers inline.

Example

use smallvec::SmallVec;
let mut v = SmallVec::<[u8; 4]>::new(); // initialize an empty vector

// The vector can hold up to 4 items without spilling onto the heap.
v.extend(0..4);
assert_eq!(v.len(), 4);
assert!(!v.spilled());

// Pushing another element will force the buffer to spill:
v.push(4);
assert_eq!(v.len(), 5);
assert!(v.spilled());

Methods

impl<A: Array> SmallVec<A>

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

pub fn new() -> SmallVec<A>

Construct an empty vector

pub fn with_capacity(n: usize) -> Self

Construct an empty vector with enough capacity pre-allocated to store at least n elements.

Will create a heap allocation only if n is larger than the inline capacity.

let v: SmallVec<[u8; 3]> = SmallVec::with_capacity(100);

assert!(v.is_empty());
assert!(v.capacity() >= 100);

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

pub fn from_vec(vec: Vec<A::Item>) -> SmallVec<A>

Construct a new SmallVec from a Vec<A::Item>.

Elements will be copied to the inline buffer if vec.capacity() <= A::size().

use smallvec::SmallVec;

let vec = vec![1, 2, 3, 4, 5];
let small_vec: SmallVec<[_; 3]> = SmallVec::from_vec(vec);

assert_eq!(&*small_vec, &[1, 2, 3, 4, 5]);

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

pub fn from_buf(buf: A) -> SmallVec<A>

Constructs a new SmallVec on the stack from an A without copying elements.

use smallvec::SmallVec;

let buf = [1, 2, 3, 4, 5];
let small_vec: SmallVec<_> = SmallVec::from_buf(buf);

assert_eq!(&*small_vec, &[1, 2, 3, 4, 5]);

pub unsafe fn set_len(&mut self, new_len: usize)

Sets the length of a vector.

This will explicitly set the size of the vector, without actually modifying its buffers, so it is up to the caller to ensure that the vector is actually the specified size.

pub fn inline_size(&self) -> usize

The maximum number of elements this vector can hold inline

pub fn len(&self) -> usize

The number of elements stored in the vector

pub fn is_empty(&self) -> bool

Returns true if the vector is empty

pub fn capacity(&self) -> usize

The number of items the vector can hold without reallocating

pub fn spilled(&self) -> bool

Returns true if the data has spilled into a separate heap-allocated buffer.

Important traits for Drain<'a, T>

impl<'a, T: 'a> Iterator for Drain<'a, T> type Item = T;

pub fn drain(&mut self) -> Drain<A::Item>

Empty the vector and return an iterator over its former contents.

pub fn push(&mut self, value: A::Item)

Append an item to the vector.

pub fn pop(&mut self) -> Option<A::Item>

Remove an item from the end of the vector and return it, or None if empty.

pub fn grow(&mut self, new_cap: usize)

Re-allocate to set the capacity to max(new_cap, inline_size()).

Panics if new_cap is less than the vector's length.

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

Reserve capacity for additional more elements to be inserted.

May reserve more space to avoid frequent reallocations.

If the new capacity would overflow usize then it will be set to usize::max_value() instead. (This means that inserting additional new elements is not guaranteed to be possible after calling this function.)

pub fn reserve_exact(&mut self, additional: usize)

Reserve the minumum capacity for additional more elements to be inserted.

Panics if the new capacity overflows usize.

pub fn shrink_to_fit(&mut self)

Shrink the capacity of the vector as much as possible.

When possible, this will move data from an external heap buffer to the vector's inline storage.

pub fn truncate(&mut self, len: usize)

Shorten the vector, keeping the first len elements and dropping the rest.

If len is greater than or equal to the vector's current length, this has no effect.

This does not re-allocate. If you want the vector's capacity to shrink, call shrink_to_fit after truncating.

pub fn as_slice(&self) -> &[A::Item]

Extracts a slice containing the entire vector.

Equivalent to &s[..].

pub fn as_mut_slice(&mut self) -> &mut [A::Item]

Extracts a mutable slice of the entire vector.

Equivalent to &mut s[..].

pub fn swap_remove(&mut self, index: usize) -> A::Item

Remove the element at position index, replacing it with the last element.

This does not preserve ordering, but is O(1).

Panics if index is out of bounds.

pub fn clear(&mut self)

Remove all elements from the vector.

pub fn remove(&mut self, index: usize) -> A::Item

Remove and return the element at position index, shifting all elements after it to the left.

Panics if index is out of bounds.

pub fn insert(&mut self, index: usize, element: A::Item)

Insert an element at position index, shifting all elements after it to the right.

Panics if index is out of bounds.

pub fn insert_many<I: IntoIterator<Item = A::Item>>(     &mut self,     index: usize,     iterable: I )

Insert multiple elements at position index, shifting all following elements toward the back.

pub fn into_vec(self) -> Vec<A::Item>

Convert a SmallVec to a Vec, without reallocating if the SmallVec has already spilled onto the heap.

pub fn retain<F: FnMut(&mut A::Item) -> bool>(&mut self, f: F)

Retains only the elements specified by the predicate.

In other words, remove all elements e such that f(&e) returns false. This method operates in place and preserves the order of the retained elements.

pub fn dedup(&mut self) where     A::Item: PartialEq<A::Item>,

Removes consecutive duplicate elements.

pub fn dedup_by<F>(&mut self, same_bucket: F) where     F: FnMut(&mut A::Item, &mut A::Item) -> bool,

Removes consecutive duplicate elements using the given equality relation.

pub fn dedup_by_key<F, K>(&mut self, key: F) where     F: FnMut(&mut A::Item) -> K,     K: PartialEq<K>,

Removes consecutive elements that map to the same key.

impl<A: Array> SmallVec<A> where     A::Item: Copy,

pub fn from_slice(slice: &[A::Item]) -> Self

Copy the elements from a slice into a new SmallVec.

For slices of Copy types, this is more efficient than SmallVec::from(slice).

pub fn insert_from_slice(&mut self, index: usize, slice: &[A::Item])

Copy elements from a slice into the vector at position index, shifting any following elements toward the back.

For slices of Copy types, this is more efficient than insert.

pub fn extend_from_slice(&mut self, slice: &[A::Item])

Copy elements from a slice and append them to the vector.

For slices of Copy types, this is more efficient than extend.

impl<A: Array> SmallVec<A> where     A::Item: Clone,

pub fn resize(&mut self, len: usize, value: A::Item)

Resizes the vector so that its length is equal to len.

If len is less than the current length, the vector simply truncated.

If len is greater than the current length, value is appended to the vector until its length equals len.

pub fn from_elem(elem: A::Item, n: usize) -> Self

Creates a SmallVec with n copies of elem.

use smallvec::SmallVec;

let v = SmallVec::<[char; 128]>::from_elem('d', 2);
assert_eq!(v, SmallVec::from_buf(['d', 'd']));

Methods from Deref<Target = [A::Item]>

pub fn len(&self) -> usize

Returns the number of elements in the slice.

Examples

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

pub fn is_empty(&self) -> bool

Returns true if the slice has a length of 0.

Examples

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

Examples

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

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

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

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

• If given a position, returns a reference to the element at that position or None if out of bounds.
• If given a range, returns the subslice corresponding to that range, or None if out of bounds.

Examples

let v = [10, 40, 30];
assert_eq!(Some(&40), v.get(1));
assert_eq!(Some(&[10, 40][..]), v.get(0..2));
assert_eq!(None, v.get(3));
assert_eq!(None, v.get(0..4));

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

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

Examples

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

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

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

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

This is generally not recommended, use with caution! For a safe alternative see get.

Examples

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

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

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

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

This is generally not recommended, use with caution! For a safe alternative see get_mut.

Examples

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

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

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

Returns a raw pointer to the slice's buffer.

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

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.offset(i as isize));
    }
}

pub fn as_mut_ptr(&mut self) -> *mut T

Returns an unsafe mutable pointer to the slice's buffer.

The caller must ensure that the slice outlives the pointer this function returns, or else it will end up pointing to garbage.

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

Examples

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

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

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

Swaps two elements in the slice.

Arguments

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

Panics

Panics if a or b are out of bounds.

Examples

let mut v = ["a", "b", "c", "d"];
v.swap(1, 3);
assert!(v == ["a", "d", "c", "b"]);

pub fn reverse(&mut self)

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

Examples

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

pub fn iter(&self) -> Iter<T>

Returns an iterator over the slice.

Examples

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

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

pub fn iter_mut(&mut self) -> IterMut<T>

Returns an iterator that allows modifying each value.

Examples

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

pub fn windows(&self, size: usize) -> Windows<T>

Returns an iterator over all contiguous windows of length size. The windows overlap. If the slice is shorter than size, the iterator returns no values.

Panics

Panics if size is 0.

Examples

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

If the slice is shorter than size:

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

pub fn chunks(&self, chunk_size: usize) -> Chunks<T>

Returns an iterator over chunk_size elements of the slice at a time. 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 exact_chunks for a variant of this iterator that returns chunks of always exactly chunk_size elements.

Panics

Panics if chunk_size is 0.

Examples

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

pub fn exact_chunks(&self, chunk_size: usize) -> ExactChunks<T>

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

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

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

Panics

Panics if chunk_size is 0.

Examples

#![feature(exact_chunks)]

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

pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T>

Returns an iterator over chunk_size elements of the slice at a time. 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 exact_chunks_mut for a variant of this iterator that returns chunks of always exactly chunk_size elements.

Panics

Panics if chunk_size is 0.

Examples

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

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

pub fn exact_chunks_mut(&mut self, chunk_size: usize) -> ExactChunksMut<T>

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

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

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.

Panics

Panics if chunk_size is 0.

Examples

#![feature(exact_chunks)]

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

for chunk in v.exact_chunks_mut(2) {
    for elem in chunk.iter_mut() {
        *elem += count;
    }
    count += 1;
}
assert_eq!(v, &[1, 1, 2, 2, 0]);

pub fn split_at(&self, mid: usize) -> (&[T], &[T])

Divides one slice into two at an index.

The first will contain all indices from [0, mid) (excluding the index mid itself) and the second will contain all indices from [mid, len) (excluding the index len itself).

Panics

Panics if mid > len.

Examples

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

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

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

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

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

Divides one mutable slice into two at an index.

The first will contain all indices from [0, mid) (excluding the index mid itself) and the second will contain all indices from [mid, len) (excluding the index len itself).

Panics

Panics if mid > len.

Examples

let mut v = [1, 0, 3, 0, 5, 6];
// scoped to restrict the lifetime of the borrows
{
    let (left, right) = v.split_at_mut(2);
    assert!(left == [1, 0]);
    assert!(right == [3, 0, 5, 6]);
    left[1] = 2;
    right[1] = 4;
}
assert!(v == [1, 2, 3, 4, 5, 6]);

pub fn split<F>(&self, pred: F) -> Split<T, F> where     F: FnMut(&T) -> bool,

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

Examples

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

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

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

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

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

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

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

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

pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F> where     F: FnMut(&T) -> bool,

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

Examples

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

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

pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F> where     F: FnMut(&T) -> bool,

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

Examples

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

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

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

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

pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F> where     F: FnMut(&T) -> bool,

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

Examples

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

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

pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once by numbers divisible by 3 (i.e. [10, 40], [20, 60, 50]):

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

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

pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

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]);

pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

Print the slice split once, starting from the end, by numbers divisible by 3 (i.e. [50], [10, 40, 30, 20]):

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

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

pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F> where     F: FnMut(&T) -> bool,

Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.

The last element returned, if any, will contain the remainder of the slice.

Examples

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

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

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

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

Examples

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

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

Returns true if needle is a prefix of the slice.

Examples

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

Always returns true if needle is an empty slice:

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

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

Returns true if needle is a suffix of the slice.

Examples

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

Always returns true if needle is an empty slice:

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

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

Binary searches this sorted slice for a given element.

If the value is found then Ok is returned, containing the index of the matching element; if the value is not found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

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, });

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

Binary searches this sorted slice with a comparator function.

The comparator function should implement an order consistent with the sort order of the underlying slice, returning an order code that indicates whether its argument is Less, Equal or Greater the desired target.

If a matching value is found then returns Ok, containing the index for the matched element; if no match is found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

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, });

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

Binary searches this sorted slice with a key extraction function.

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

If a matching value is found then returns Ok, containing the index for the matched element; if no match is found then Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

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, });

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

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

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

Current implementation

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

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

Examples

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

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

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

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

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

Current implementation

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

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

Examples

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

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

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

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

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

Current implementation

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

Examples

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

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

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

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

Panics

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

Complexity

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

Examples

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

Rotating a subslice:

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

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

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

Panics

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

Complexity

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

Examples

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

Rotate a subslice:

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

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

Copies the elements from src into self.

The length of src must be the same as self.

If src implements Copy, it can be more performant to use copy_from_slice.

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];

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]);

pub fn copy_from_slice(&mut self, src: &[T]) where     T: Copy,

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

The length of src must be the same as self.

If src 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];

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]);

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

Swaps all elements in self with those in other.

The length of other must be the same as self.

Panics

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

Example

Swapping two elements across slices:

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

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

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

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

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

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

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

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

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

Trait Implementations

impl<A: Array> Deref for SmallVec<A>

type Target = [A::Item]

The resulting type after dereferencing.

fn deref(&self) -> &[A::Item]

Dereferences the value.

impl<A: Array> DerefMut for SmallVec<A>

fn deref_mut(&mut self) -> &mut [A::Item]

Mutably dereferences the value.

impl<A: Array> AsRef<[A::Item]> for SmallVec<A>

fn as_ref(&self) -> &[A::Item]

Performs the conversion.

impl<A: Array> AsMut<[A::Item]> for SmallVec<A>

fn as_mut(&mut self) -> &mut [A::Item]

Performs the conversion.

impl<A: Array> Borrow<[A::Item]> for SmallVec<A>

fn borrow(&self) -> &[A::Item]

Immutably borrows from an owned value.

impl<A: Array> BorrowMut<[A::Item]> for SmallVec<A>

fn borrow_mut(&mut self) -> &mut [A::Item]

Mutably borrows from an owned value.

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this object, returning how many bytes were written.

fn write_all(&mut self, buf: &[u8]) -> Result<()>

Attempts to write an entire buffer into this write.

fn flush(&mut self) -> Result<()>

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

fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>

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

fn by_ref(&mut self) -> &mut Self

Creates a "by reference" adaptor for this instance of Write.

impl<'a, A: Array> From<&'a [A::Item]> for SmallVec<A> where     A::Item: Clone,

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn from(slice: &'a [A::Item]) -> SmallVec<A>

Performs the conversion.

impl<A: Array> From<Vec<A::Item>> for SmallVec<A>

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn from(vec: Vec<A::Item>) -> SmallVec<A>

Performs the conversion.

impl<A: Array> From<A> for SmallVec<A>

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn from(array: A) -> SmallVec<A>

Performs the conversion.

impl<A: Array> Index<usize> for SmallVec<A>

type Output = A::Item

The returned type after indexing.

fn index(&self, index: usize) -> &A::Item

Performs the indexing (container[index]) operation.

impl<A: Array> IndexMut<usize> for SmallVec<A>

fn index_mut(&mut self, index: usize) -> &mut A::Item

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

impl<A: Array> Index<Range<usize>> for SmallVec<A>

type Output = [A::Item]

The returned type after indexing.

fn index(&self, index: Range<usize>) -> &[A::Item]

Performs the indexing (container[index]) operation.

impl<A: Array> IndexMut<Range<usize>> for SmallVec<A>

fn index_mut(&mut self, index: Range<usize>) -> &mut [A::Item]

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

impl<A: Array> Index<RangeFrom<usize>> for SmallVec<A>

type Output = [A::Item]

The returned type after indexing.

fn index(&self, index: RangeFrom<usize>) -> &[A::Item]

Performs the indexing (container[index]) operation.

impl<A: Array> IndexMut<RangeFrom<usize>> for SmallVec<A>

fn index_mut(&mut self, index: RangeFrom<usize>) -> &mut [A::Item]

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

impl<A: Array> Index<RangeTo<usize>> for SmallVec<A>

type Output = [A::Item]

The returned type after indexing.

fn index(&self, index: RangeTo<usize>) -> &[A::Item]

Performs the indexing (container[index]) operation.

impl<A: Array> IndexMut<RangeTo<usize>> for SmallVec<A>

fn index_mut(&mut self, index: RangeTo<usize>) -> &mut [A::Item]

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

impl<A: Array> Index<RangeFull> for SmallVec<A>

type Output = [A::Item]

The returned type after indexing.

fn index(&self, index: RangeFull) -> &[A::Item]

Performs the indexing (container[index]) operation.

impl<A: Array> IndexMut<RangeFull> for SmallVec<A>

fn index_mut(&mut self, index: RangeFull) -> &mut [A::Item]

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

impl<A: Array> ExtendFromSlice<A::Item> for SmallVec<A> where     A::Item: Copy,

fn extend_from_slice(&mut self, other: &[A::Item])

Extends a collection from a slice of its element type

impl<A: Array> VecLike<A::Item> for SmallVec<A>

fn push(&mut self, value: A::Item)

Deprecated

: Use Extend and Deref<[T]> instead

Append an element to the vector.

impl<A: Array> FromIterator<A::Item> for SmallVec<A>

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn from_iter<I: IntoIterator<Item = A::Item>>(iterable: I) -> SmallVec<A>

Creates a value from an iterator.

impl<A: Array> Extend<A::Item> for SmallVec<A>

fn extend<I: IntoIterator<Item = A::Item>>(&mut self, iterable: I)

Extends a collection with the contents of an iterator.

impl<A: Array> Debug for SmallVec<A> where     A::Item: Debug,

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<A: Array> Default for SmallVec<A>

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn default() -> SmallVec<A>

Returns the "default value" for a type.

impl<A: Array> Drop for SmallVec<A>

fn drop(&mut self)

Executes the destructor for this type.

impl<A: Array> Clone for SmallVec<A> where     A::Item: Clone,

Important traits for SmallVec<A>

impl<A: Array<Item = u8>> Write for SmallVec<A>

fn clone(&self) -> SmallVec<A>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<A: Array, B: Array> PartialEq<SmallVec<B>> for SmallVec<A> where     A::Item: PartialEq<B::Item>,

fn eq(&self, other: &SmallVec<B>) -> bool

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

fn ne(&self, other: &SmallVec<B>) -> bool

This method tests for !=.

impl<A: Array> Eq for SmallVec<A> where     A::Item: Eq,

impl<A: Array> PartialOrd for SmallVec<A> where     A::Item: PartialOrd,

fn partial_cmp(&self, other: &SmallVec<A>) -> Option<Ordering>

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

fn lt(&self, other: &Rhs) -> bool

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

fn le(&self, other: &Rhs) -> bool

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

fn gt(&self, other: &Rhs) -> bool

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

fn ge(&self, other: &Rhs) -> bool

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

impl<A: Array> Ord for SmallVec<A> where     A::Item: Ord,

fn cmp(&self, other: &SmallVec<A>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

impl<A: Array> Hash for SmallVec<A> where     A::Item: Hash,

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where     H: Hasher,

Feeds a slice of this type into the given [Hasher].

impl<A: Array> Send for SmallVec<A> where     A::Item: Send,

impl<A: Array> IntoIterator for SmallVec<A>

type IntoIter = IntoIter<A>

Which kind of iterator are we turning this into?

type Item = A::Item

The type of the elements being iterated over.

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, A: Array> IntoIterator for &'a SmallVec<A>

type IntoIter = Iter<'a, A::Item>

Which kind of iterator are we turning this into?

type Item = &'a A::Item

The type of the elements being iterated over.

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, A: Array> IntoIterator for &'a mut SmallVec<A>

type IntoIter = IterMut<'a, A::Item>

Which kind of iterator are we turning this into?

type Item = &'a mut A::Item

The type of the elements being iterated over.

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.