Struct std::collections::Deque

A double-ended queue (growable ring buffer).

Elements can be efficiently pushed to and popped from either end of the queue.

Example

use std::collections::Deque;

let deque: Deque<i32> = Deque::new();
defer deque.free();

deque.push(1);
deque.push(2);
deque.push_front(3);
deque.push_front(4);

assert_eq!(deque.len(), 4);

assert_eq!(deque.pop(), Option::some(2));
assert_eq!(deque.pop_front(), Option::some(4));
assert_eq!(deque.pop(), Option::some(1));
assert_eq!(deque.pop_front(), Option::some(3));
Run this example

Methods

• fn new() -> Deque<T>

  source

  Create an empty deque

  This will not allocate until the first element is inserted.

• fn with_capacity(capacity: usize) -> Deque<T>

  source

  Create a deque that can hold up to capacity elements without reallocating.

• fn from_slice(slice: &[T]) -> Deque<T>

  source

  Create a deque from a slice, copying the elements.

• fn from_iter<I>(iter: &mut I) -> Deque<T>

  I: Iterator<I, T>

  source

  Create a deque from an iterator of elements.

• fn reserve(self: &mut Deque<T>, additional: usize)

  source

  Reserve capacity for at least additional elements.

• fn shrink_to_fit(self: &mut Deque<T>)

  source

  Shrink the size of the underlying buffer to the minimum size needed to hold the current elements.

• fn len(self: &Deque<T>) -> usize

  source

  Returns the number of elements in the deque.

• fn capacity(self: &Deque<T>) -> usize

  source

  Returns the total number of elements that the deque can hold without reallocating.

• fn is_empty(self: &Deque<T>) -> bool

  source

  Returns true if the deque is empty, false otherwise.

• fn clear(self: &mut Deque<T>)

  source

  Clears the deque, removing all values.

  This does not shrink the underlying buffer, call shrink_to_fit to free up unused memory.

• fn as_slices(self: &Deque<T>) -> (&[T], &[T])

  source

  Returns a pair of slices that represent the deque's contents in order.

  If the deque has not wrapped around (elements are contiguous in memory), the second slice will be empty.

• fn as_slices_mut(self: &mut Deque<T>) -> (&mut [T], &mut [T])

  source

  Returns a pair of mutable slices that represent the deque's contents in order.

  If the deque has not wrapped around (elements are contiguous in memory), the second slice will be empty.

• fn push(self: &mut Deque<T>, element: T)

  source

  Pushes an element to the back of the deque.

• fn pop(self: &mut Deque<T>) -> Option<T>

  source

  Pops an element from the back of the deque.

  If the queue is empty, returns Option::none().

• fn push_front(self: &mut Deque<T>, element: T)

  source

  Pushes an element to the front of the deque.

• fn pop_front(self: &mut Deque<T>) -> Option<T>

  source

  Pops an element from the front of the deque.

  If the queue is empty, returns Option::none().

• fn iter(self: &Deque<T>) -> DequeIterator<T>

  source

  Returns an iterator over the elements of this iterable.

  See Iterable for details.

• fn iter_ref(self: &Deque<T>) -> DequeRefIterator<&T>

  source

  Returns an iterator over the pointers of the items of this iterable.

  See IterableRef for details.

• fn iter_mut(self: &mut Deque<T>) -> DequeRefIterator<&mut T>

  source

  Returns an iterator over mutable pointers to the elements of the collection.

  See IterableMut for details.

• fn extend<I>(self: &mut Deque<T>, iter: &mut I)

  I: Iterator<I, T>

  source

  Extends the deque on the back end with the contents of an iterator.

• fn extend_front<I>(self: &mut Deque<T>, iter: &mut I)

  I: Iterator<I, T>

  source

  Extends the deque on the front end with the contents of an iterator.

• fn extend_from_slice(self: &mut Deque<T>, value: &[T])

  source

  Extends the deque on the back end with the contents of a slice.

• fn retain<F>(self: &mut Deque<T>, func: F)

  F: Fn(&T) -> bool

  source

  Removes the elements not mathing the given predicate.

  Does not remove excess capacity, call shrink_to_fit afterwards, if this is desired.

  Example

  use std::collections::Deque;
  
  let queue: Deque<i32> = Deque::from_iter(&(0..=6));
  defer queue.free();
  
  queue.retain(|x: &i32| -> bool { *x % 2 == 0 });
  
  assert_eq!(queue.len(), 4);
  let iter = queue.iter();
  assert_eq!(iter.next(), Option::some(0));
  assert_eq!(iter.next(), Option::some(2));
  assert_eq!(iter.next(), Option::some(4));
  assert_eq!(iter.next(), Option::some(6));
  assert_eq!(iter.next(), Option::none());
  Run this example

• fn move(self: &mut Deque<T>) -> Deque<T>

  source

  Creates a copy of the object, leaving an inert object behind.

  See Movable for details.

• fn free(self: &mut Deque<T>)

  source

  Frees the memory backing the object.

• fn free_all(self: &mut Deque<T>)

  source

  Helper for collections that own heap-allocated objects. This is used to be able to do defer col.free_all() without much boilerplate.

  Example

  use std::collections::Deque;
  use std::string::StringBuf;
  use std::fmt::format;
  
  let v: Deque<StringBuf> = Deque::new();
  defer v.free_all();
  
  for i in 1..10 {
      v.push("{} + {} = {}".format!(i, i, i + i).unwrap());
  }
  Run this example

• fn clone(self: &Deque<T>) -> Deque<T>

  source

  Returns a copy of the object.