Struct std::vec::VecStable
[-] [+]
[src]
pub struct Vec<T> { // some fields omitted }
A growable list type, written Vec<T>
but pronounced 'vector.'
Examples
fn main() { let mut vec = Vec::new(); vec.push(1); vec.push(2); assert_eq!(vec.len(), 2); assert_eq!(vec[0], 1); assert_eq!(vec.pop(), Some(2)); assert_eq!(vec.len(), 1); vec[0] = 7; assert_eq!(vec[0], 7); vec.push_all(&[1, 2, 3]); for x in vec.iter() { println!("{}", x); } assert_eq!(vec, vec![7, 1, 2, 3]); }let mut vec = Vec::new(); vec.push(1); vec.push(2); assert_eq!(vec.len(), 2); assert_eq!(vec[0], 1); assert_eq!(vec.pop(), Some(2)); assert_eq!(vec.len(), 1); vec[0] = 7; assert_eq!(vec[0], 7); vec.push_all(&[1, 2, 3]); for x in vec.iter() { println!("{}", x); } assert_eq!(vec, vec![7, 1, 2, 3]);
The vec!
macro is provided to make initialization more convenient:
let mut vec = vec![1, 2, 3]; vec.push(4); assert_eq!(vec, vec![1, 2, 3, 4]);
Use a Vec<T>
as an efficient stack:
let mut stack = Vec::new(); stack.push(1); stack.push(2); stack.push(3); loop { let top = match stack.pop() { None => break, // empty Some(x) => x, }; // Prints 3, 2, 1 println!("{}", top); }
Capacity and reallocation
The capacity of a vector is the amount of space allocated for any future elements that will be added onto the vector. This is not to be confused with the length of a vector, which specifies the number of actual elements within the vector. If a vector's length exceeds its capacity, its capacity will automatically be increased, but its elements will have to be reallocated.
For example, a vector with capacity 10 and length 0 would be an empty vector with space for 10
more elements. Pushing 10 or fewer elements onto the vector will not change its capacity or
cause reallocation to occur. However, if the vector's length is increased to 11, it will have
to reallocate, which can be slow. For this reason, it is recommended to use
Vec::with_capacity
whenever possible to specify how big the vector is expected to get.
Methods
impl<T> Vec<T>
fn new() -> Vec<T>
Constructs a new, empty Vec<T>
.
The vector will not allocate until elements are pushed onto it.
Examples
fn main() { let mut vec: Vec<i32> = Vec::new(); }let mut vec: Vec<i32> = Vec::new();
fn with_capacity(capacity: usize) -> Vec<T>
Constructs a new, empty Vec<T>
with the specified capacity.
The vector will be able to hold exactly capacity
elements without reallocating. If
capacity
is 0, the vector will not allocate.
It is important to note that this function does not specify the length of the returned
vector, but only the capacity. (For an explanation of the difference between length and
capacity, see the main Vec<T>
docs above, 'Capacity and reallocation'.)
Examples
fn main() { let mut vec: Vec<_> = Vec::with_capacity(10); // The vector contains no items, even though it has capacity for more assert_eq!(vec.len(), 0); // These are all done without reallocating... for i in 0..10 { vec.push(i); } // ...but this may make the vector reallocate vec.push(11); }let mut vec: Vec<_> = Vec::with_capacity(10); // The vector contains no items, even though it has capacity for more assert_eq!(vec.len(), 0); // These are all done without reallocating... for i in 0..10 { vec.push(i); } // ...but this may make the vector reallocate vec.push(11);
unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T>
Creates a Vec<T>
directly from the raw components of another vector.
This is highly unsafe, due to the number of invariants that aren't checked.
Examples
use std::ptr; use std::mem; fn main() { let mut v = vec![1, 2, 3]; // Pull out the various important pieces of information about `v` let p = v.as_mut_ptr(); let len = v.len(); let cap = v.capacity(); unsafe { // Cast `v` into the void: no destructor run, so we are in // complete control of the allocation to which `p` points. mem::forget(v); // Overwrite memory with 4, 5, 6 for i in 0..len as isize { ptr::write(p.offset(i), 4 + i); } // Put everything back together into a Vec let rebuilt = Vec::from_raw_parts(p, len, cap); assert_eq!(rebuilt, vec![4, 5, 6]); } }use std::ptr; use std::mem; fn main() { let mut v = vec![1, 2, 3]; // Pull out the various important pieces of information about `v` let p = v.as_mut_ptr(); let len = v.len(); let cap = v.capacity(); unsafe { // Cast `v` into the void: no destructor run, so we are in // complete control of the allocation to which `p` points. mem::forget(v); // Overwrite memory with 4, 5, 6 for i in 0..len as isize { ptr::write(p.offset(i), 4 + i); } // Put everything back together into a Vec let rebuilt = Vec::from_raw_parts(p, len, cap); assert_eq!(rebuilt, vec![4, 5, 6]); } }
unsafe fn from_raw_buf(ptr: *const T, elts: usize) -> Vec<T>
Creates a vector by copying the elements from a raw pointer.
This function will copy elts
contiguous elements starting at ptr
into a new allocation
owned by the returned Vec<T>
. The elements of the buffer are copied into the vector
without cloning, as if ptr::read()
were called on them.
fn capacity(&self) -> usize
Returns the number of elements the vector can hold without reallocating.
Examples
fn main() { let vec: Vec<i32> = Vec::with_capacity(10); assert_eq!(vec.capacity(), 10); }let vec: Vec<i32> = Vec::with_capacity(10); assert_eq!(vec.capacity(), 10);
fn reserve(&mut self, additional: usize)
Reserves capacity for at least additional
more elements to be inserted in the given
Vec<T>
. The collection may reserve more space to avoid frequent reallocations.
Panics
Panics if the new capacity overflows usize
.
Examples
fn main() { let mut vec = vec![1]; vec.reserve(10); assert!(vec.capacity() >= 11); }let mut vec = vec![1]; vec.reserve(10); assert!(vec.capacity() >= 11);
fn reserve_exact(&mut self, additional: usize)
Reserves the minimum capacity for exactly additional
more elements to
be inserted in the given Vec<T>
. 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 overflows usize
.
Examples
fn main() { let mut vec = vec![1]; vec.reserve_exact(10); assert!(vec.capacity() >= 11); }let mut vec = vec![1]; vec.reserve_exact(10); assert!(vec.capacity() >= 11);
fn shrink_to_fit(&mut self)
Shrinks the capacity of the vector as much as possible.
It will drop down as close as possible to the length but the allocator may still inform the vector that there is space for a few more elements.
Examples
fn main() { let mut vec = Vec::with_capacity(10); vec.push_all(&[1, 2, 3]); assert_eq!(vec.capacity(), 10); vec.shrink_to_fit(); assert!(vec.capacity() >= 3); }let mut vec = Vec::with_capacity(10); vec.push_all(&[1, 2, 3]); assert_eq!(vec.capacity(), 10); vec.shrink_to_fit(); assert!(vec.capacity() >= 3);
fn into_boxed_slice(self) -> Box<[T]>
Convert the vector into Box<[T]>.
Note that this will drop any excess capacity. Calling this and
converting back to a vector with into_vec()
is equivalent to calling
shrink_to_fit()
.
fn truncate(&mut self, len: usize)
Shorten a vector, dropping excess elements.
If len
is greater than the vector's current length, this has no
effect.
Examples
fn main() { let mut vec = vec![1, 2, 3, 4]; vec.truncate(2); assert_eq!(vec, vec![1, 2]); }let mut vec = vec![1, 2, 3, 4]; vec.truncate(2); assert_eq!(vec, vec![1, 2]);
fn as_mut_slice(&mut self) -> &mut [T]
Returns a mutable slice of the elements of self
.
Examples
fn main() { fn foo(slice: &mut [i32]) {} let mut vec = vec![1, 2]; foo(vec.as_mut_slice()); }fn foo(slice: &mut [i32]) {} let mut vec = vec![1, 2]; foo(vec.as_mut_slice());
fn into_iter(self) -> IntoIter<T>
Creates a consuming iterator, that is, one that moves each value out of the vector (from start to end). The vector cannot be used after calling this.
Examples
fn main() { let v = vec!["a".to_string(), "b".to_string()]; for s in v.into_iter() { // s has type String, not &String println!("{}", s); } }let v = vec!["a".to_string(), "b".to_string()]; for s in v.into_iter() { // s has type String, not &String println!("{}", s); }
unsafe fn set_len(&mut self, 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.
Examples
fn main() { let mut v = vec![1, 2, 3, 4]; unsafe { v.set_len(1); } }let mut v = vec![1, 2, 3, 4]; unsafe { v.set_len(1); }
fn swap_remove(&mut self, index: usize) -> T
Removes an element from anywhere in the vector and return it, replacing it with the last element.
This does not preserve ordering, but is O(1).
Panics
Panics if index
is out of bounds.
Examples
fn main() { let mut v = vec!["foo", "bar", "baz", "qux"]; assert_eq!(v.swap_remove(1), "bar"); assert_eq!(v, vec!["foo", "qux", "baz"]); assert_eq!(v.swap_remove(0), "foo"); assert_eq!(v, vec!["baz", "qux"]); }let mut v = vec!["foo", "bar", "baz", "qux"]; assert_eq!(v.swap_remove(1), "bar"); assert_eq!(v, vec!["foo", "qux", "baz"]); assert_eq!(v.swap_remove(0), "foo"); assert_eq!(v, vec!["baz", "qux"]);
fn insert(&mut self, index: usize, element: T)
Inserts an element at position index
within the vector, shifting all
elements after position i
one position to the right.
Panics
Panics if index
is not between 0
and the vector's length (both
bounds inclusive).
Examples
fn main() { let mut vec = vec![1, 2, 3]; vec.insert(1, 4); assert_eq!(vec, vec![1, 4, 2, 3]); vec.insert(4, 5); assert_eq!(vec, vec![1, 4, 2, 3, 5]); }let mut vec = vec![1, 2, 3]; vec.insert(1, 4); assert_eq!(vec, vec![1, 4, 2, 3]); vec.insert(4, 5); assert_eq!(vec, vec![1, 4, 2, 3, 5]);
fn remove(&mut self, index: usize) -> T
Removes and returns the element at position index
within the vector,
shifting all elements after position index
one position to the left.
Panics
Panics if i
is out of bounds.
Examples
fn main() { let mut v = vec![1, 2, 3]; assert_eq!(v.remove(1), 2); assert_eq!(v, vec![1, 3]); }let mut v = vec![1, 2, 3]; assert_eq!(v.remove(1), 2); assert_eq!(v, vec![1, 3]);
fn retain<F>(&mut self, f: F) where F: FnMut(&T), <F as FnMut(&T)>::Output == bool
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.
Examples
fn main() { let mut vec = vec![1, 2, 3, 4]; vec.retain(|&x| x%2 == 0); assert_eq!(vec, vec![2, 4]); }let mut vec = vec![1, 2, 3, 4]; vec.retain(|&x| x%2 == 0); assert_eq!(vec, vec![2, 4]);
fn push(&mut self, value: T)
Appends an element to the back of a collection.
Panics
Panics if the number of elements in the vector overflows a usize
.
Examples
fn main() { let mut vec = vec!(1, 2); vec.push(3); assert_eq!(vec, vec!(1, 2, 3)); }let mut vec = vec!(1, 2); vec.push(3); assert_eq!(vec, vec!(1, 2, 3));
fn pop(&mut self) -> Option<T>
Removes the last element from a vector and returns it, or None
if it is empty.
Examples
fn main() { let mut vec = vec![1, 2, 3]; assert_eq!(vec.pop(), Some(3)); assert_eq!(vec, vec![1, 2]); }let mut vec = vec![1, 2, 3]; assert_eq!(vec.pop(), Some(3)); assert_eq!(vec, vec![1, 2]);
fn append(&mut self, other: &mut Vec<T>)
Moves all the elements of other
into Self
, leaving other
empty.
Panics
Panics if the number of elements in the vector overflows a usize
.
Examples
fn main() { let mut vec = vec![1, 2, 3]; let mut vec2 = vec![4, 5, 6]; vec.append(&mut vec2); assert_eq!(vec, vec![1, 2, 3, 4, 5, 6]); assert_eq!(vec2, vec![]); }let mut vec = vec![1, 2, 3]; let mut vec2 = vec![4, 5, 6]; vec.append(&mut vec2); assert_eq!(vec, vec![1, 2, 3, 4, 5, 6]); assert_eq!(vec2, vec![]);
fn drain(&mut self) -> Drain<T>
Creates a draining iterator that clears the Vec
and iterates over
the removed items from start to end.
Examples
fn main() { let mut v = vec!["a".to_string(), "b".to_string()]; for s in v.drain() { // s has type String, not &String println!("{}", s); } assert!(v.is_empty()); }let mut v = vec!["a".to_string(), "b".to_string()]; for s in v.drain() { // s has type String, not &String println!("{}", s); } assert!(v.is_empty());
fn clear(&mut self)
Clears the vector, removing all values.
Examples
fn main() { let mut v = vec![1, 2, 3]; v.clear(); assert!(v.is_empty()); }let mut v = vec![1, 2, 3]; v.clear(); assert!(v.is_empty());
fn len(&self) -> usize
Returns the number of elements in the vector.
Examples
fn main() { let a = vec![1, 2, 3]; assert_eq!(a.len(), 3); }let a = vec![1, 2, 3]; assert_eq!(a.len(), 3);
fn is_empty(&self) -> bool
Returns true
if the vector contains no elements.
Examples
fn main() { let mut v = Vec::new(); assert!(v.is_empty()); v.push(1); assert!(!v.is_empty()); }let mut v = Vec::new(); assert!(v.is_empty()); v.push(1); assert!(!v.is_empty());
fn map_in_place<U, F>(self, f: F) -> Vec<U> where F: FnMut(T), <F as FnMut(T)>::Output == U
Converts a Vec<T>
to a Vec<U>
where T
and U
have the same
size and in case they are not zero-sized the same minimal alignment.
Panics
Panics if T
and U
have differing sizes or are not zero-sized and
have differing minimal alignments.
Examples
fn main() { let v = vec![0, 1, 2]; let w = v.map_in_place(|i| i + 3); assert_eq!(w.as_slice(), [3, 4, 5].as_slice()); #[derive(PartialEq, Debug)] struct Newtype(u8); let bytes = vec![0x11, 0x22]; let newtyped_bytes = bytes.map_in_place(|x| Newtype(x)); assert_eq!(newtyped_bytes.as_slice(), [Newtype(0x11), Newtype(0x22)].as_slice()); }let v = vec![0, 1, 2]; let w = v.map_in_place(|i| i + 3); assert_eq!(w.as_slice(), [3, 4, 5].as_slice()); #[derive(PartialEq, Debug)] struct Newtype(u8); let bytes = vec![0x11, 0x22]; let newtyped_bytes = bytes.map_in_place(|x| Newtype(x)); assert_eq!(newtyped_bytes.as_slice(), [Newtype(0x11), Newtype(0x22)].as_slice());
fn split_off(&mut self, at: usize) -> Vec<T>
Splits the collection into two at the given index.
Returns a newly allocated Self
. self
contains elements [0, at)
,
and the returned Self
contains elements [at, len)
.
Note that the capacity of self
does not change.
Panics
Panics if at > len
.
Examples
fn main() { let mut vec = vec![1,2,3]; let vec2 = vec.split_off(1); assert_eq!(vec, vec![1]); assert_eq!(vec2, vec![2, 3]); }let mut vec = vec![1,2,3]; let vec2 = vec.split_off(1); assert_eq!(vec, vec![1]); assert_eq!(vec2, vec![2, 3]);
impl<T> Vec<T> where T: Clone
fn resize(&mut self, new_len: usize, value: T)
Resizes the Vec
in-place so that len()
is equal to new_len
.
Calls either extend()
or truncate()
depending on whether new_len
is larger than the current value of len()
or not.
Examples
fn main() { let mut vec = vec!["hello"]; vec.resize(3, "world"); assert_eq!(vec, vec!["hello", "world", "world"]); let mut vec = vec![1, 2, 3, 4]; vec.resize(2, 0); assert_eq!(vec, vec![1, 2]); }let mut vec = vec!["hello"]; vec.resize(3, "world"); assert_eq!(vec, vec!["hello", "world", "world"]); let mut vec = vec![1, 2, 3, 4]; vec.resize(2, 0); assert_eq!(vec, vec![1, 2]);
fn push_all(&mut self, other: &[T])
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
vector is traversed in-order.
Examples
fn main() { let mut vec = vec![1]; vec.push_all(&[2, 3, 4]); assert_eq!(vec, vec![1, 2, 3, 4]); }let mut vec = vec![1]; vec.push_all(&[2, 3, 4]); assert_eq!(vec, vec![1, 2, 3, 4]);
impl<T> Vec<T> where T: PartialEq<T>
fn dedup(&mut self)
Removes consecutive repeated elements in the vector.
If the vector is sorted, this removes all duplicates.
Examples
fn main() { let mut vec = vec![1, 2, 2, 3, 2]; vec.dedup(); assert_eq!(vec, vec![1, 2, 3, 2]); }let mut vec = vec![1, 2, 2, 3, 2]; vec.dedup(); assert_eq!(vec, vec![1, 2, 3, 2]);
Trait Implementations
impl<T> Borrow<[T]> for Vec<T>
impl<T> BorrowMut<[T]> for Vec<T>
fn borrow_mut(&mut self) -> &mut [T]
impl<T> Send for Vec<T> where T: Send
impl<T> Sync for Vec<T> where T: Sync
impl<T> Clone for Vec<T> where T: Clone
fn clone(&self) -> Vec<T>
fn clone_from(&mut self, other: &Vec<T>)
fn clone_from(&mut self, &Vec<T>)
impl<T> Hash for Vec<T> where T: Hash
fn hash<H>(&self, state: &mut H) where H: Hasher
fn hash_slice<H>(&[Vec<T>], &mut H) where H: Hasher, Vec<T>: Sized
impl<T> Index<usize> for Vec<T>
impl<T> IndexMut<usize> for Vec<T>
impl<T> Index<Range<usize>> for Vec<T>
impl<T> Index<RangeTo<usize>> for Vec<T>
impl<T> Index<RangeFrom<usize>> for Vec<T>
impl<T> Index<RangeFull> for Vec<T>
impl<T> IndexMut<Range<usize>> for Vec<T>
impl<T> IndexMut<RangeTo<usize>> for Vec<T>
impl<T> IndexMut<RangeFrom<usize>> for Vec<T>
impl<T> IndexMut<RangeFull> for Vec<T>
impl<T> Deref for Vec<T>
impl<T> DerefMut for Vec<T>
impl<T> FromIterator<T> for Vec<T>
fn from_iter<I>(iterable: I) -> Vec<T> where I: IntoIterator, <I as IntoIterator>::Item == T
impl<T> IntoIterator for Vec<T>
impl<T> Extend<T> for Vec<T>
fn extend<I>(&mut self, iterable: I) where I: IntoIterator, <I as IntoIterator>::Item == T
impl<A, B> PartialEq<Vec<B>> for Vec<A> where A: PartialEq<B>
fn eq(&self, other: &Vec<B>) -> bool
fn ne(&self, other: &Vec<B>) -> bool
fn ne(&self, &Vec<B>) -> bool
impl<'b, A, B> PartialEq<&'b [B]> for Vec<A> where A: PartialEq<B>
fn eq(&self, other: &&'b [B]) -> bool
fn ne(&self, other: &&'b [B]) -> bool
fn ne(&self, &&'b [B]) -> bool
impl<'b, A, B> PartialEq<&'b mut [B]> for Vec<A> where A: PartialEq<B>
fn eq(&self, other: &&'b mut [B]) -> bool
fn ne(&self, other: &&'b mut [B]) -> bool
fn ne(&self, &&'b mut [B]) -> bool
impl<'a, A, B> PartialEq<Cow<'a, [A]>> for Vec<B> where A: Clone, B: PartialEq<A>
fn eq(&self, other: &Cow<'a, [A]>) -> bool
fn ne(&self, other: &Cow<'a, [A]>) -> bool
fn ne(&self, &Cow<'a, [A]>) -> bool
impl<T> PartialOrd<Vec<T>> for Vec<T> where T: PartialOrd<T>
fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering>
fn lt(&self, &Vec<T>) -> bool
fn le(&self, &Vec<T>) -> bool
fn gt(&self, &Vec<T>) -> bool
fn ge(&self, &Vec<T>) -> bool
impl<T> Eq for Vec<T> where T: Eq
fn assert_receiver_is_total_eq(&self)
impl<T> Ord for Vec<T> where T: Ord
impl<T> AsSlice<T> for Vec<T>
fn as_slice(&self) -> &[T]
Returns a slice into self
.
Examples
fn main() { fn foo(slice: &[i32]) {} let vec = vec![1, 2]; foo(vec.as_slice()); }fn foo(slice: &[i32]) {} let vec = vec![1, 2]; foo(vec.as_slice());