Struct im::Vector

pub struct Vector<A> { /* private fields */ }

A persistent vector.

This is a sequence of elements in insertion order - if you need a list of things, any kind of list of things, this is what you’re looking for.

It’s implemented as an RRB vector with smart head/tail chunking. In performance terms, this means that practically every operation is O(log n), except push/pop on both sides, which will be O(1) amortised, and O(log n) in the worst case. In practice, the push/pop operations will be blindingly fast, nearly on par with the native VecDeque, and other operations will have decent, if not high, performance, but they all have more or less the same O(log n) complexity, so you don’t need to keep their performance characteristics in mind - everything, even splitting and merging, is safe to use and never too slow.

Performance Notes

Because of the head/tail chunking technique, until you push a number of items above double the tree’s branching factor (that’s self.len() = 2 × k (where k = 64) = 128) on either side, the data structure is still just a handful of arrays, not yet an RRB tree, so you’ll see performance and memory characteristics similar to Vec or VecDeque.

This means that the structure always preallocates four chunks of size k (k being the tree’s branching factor), equivalent to a Vec with an initial capacity of 256. Beyond that, it will allocate tree nodes of capacity k as needed.

In addition, vectors start out as single chunks, and only expand into the full data structure once you go past the chunk size. This makes them perform identically to Vec at small sizes.

Implementations

impl<A: Clone> Vector<A>

pub fn new() -> Self

Construct an empty vector.

pub fn len(&self) -> usize

Get the length of a vector.

Time: O(1)

Examples

assert_eq!(5, vector![1, 2, 3, 4, 5].len());

pub fn is_empty(&self) -> bool

Test whether a vector is empty.

Time: O(1)

Examples

let vec = vector!["Joe", "Mike", "Robert"];
assert_eq!(false, vec.is_empty());
assert_eq!(true, Vector::<i32>::new().is_empty());

pub fn is_inline(&self) -> bool

Test whether a vector is currently inlined.

Vectors small enough that their contents could be stored entirely inside the space of std::mem::size_of::<Vector<A>>() bytes are stored inline on the stack instead of allocating any chunks. This method returns true if this vector is currently inlined, or false if it currently has chunks allocated on the heap.

This may be useful in conjunction with ptr_eq(), which checks if two vectors’ heap allocations are the same, and thus will never return true for inlined vectors.

Time: O(1)

pub fn ptr_eq(&self, other: &Self) -> bool

Test whether two vectors refer to the same content in memory.

This uses the following rules to determine equality:

• If the two sides are references to the same vector, return true.
• If the two sides are single chunk vectors pointing to the same chunk, return true.
• If the two sides are full trees pointing to the same chunks, return true.

This would return true if you’re comparing a vector to itself, or if you’re comparing a vector to a fresh clone of itself. The exception to this is if you’ve cloned an inline array (ie. an array with so few elements they can fit inside the space a Vector allocates for its pointers, so there are no heap allocations to compare).

Time: O(1)

pub fn iter(&self) -> Iter<'_, A>

Get an iterator over a vector.

Time: O(1)

pub fn iter_mut(&mut self) -> IterMut<'_, A>

Get a mutable iterator over a vector.

Time: O(1)

pub fn leaves(&self) -> Chunks<'_, A>

Get an iterator over the leaf nodes of a vector.

This returns an iterator over the Chunks at the leaves of the RRB tree. These are useful for efficient parallelisation of work on the vector, but should not be used for basic iteration.

Time: O(1)

pub fn leaves_mut(&mut self) -> ChunksMut<'_, A>

Get a mutable iterator over the leaf nodes of a vector. This returns an iterator over the Chunks at the leaves of the RRB tree. These are useful for efficient parallelisation of work on the vector, but should not be used for basic iteration.

Time: O(1)

pub fn focus(&self) -> Focus<'_, A>

Construct a Focus for a vector.

Time: O(1)

pub fn focus_mut(&mut self) -> FocusMut<'_, A>

Construct a FocusMut for a vector.

Time: O(1)

pub fn get(&self, index: usize) -> Option<&A>

Get a reference to the value at index index in a vector.

Returns None if the index is out of bounds.

Time: O(log n)

Examples

let vec = vector!["Joe", "Mike", "Robert"];
assert_eq!(Some(&"Robert"), vec.get(2));
assert_eq!(None, vec.get(5));

pub fn get_mut(&mut self, index: usize) -> Option<&mut A>

Get a mutable reference to the value at index index in a vector.

Returns None if the index is out of bounds.

Time: O(log n)

Examples

let mut vec = vector!["Joe", "Mike", "Robert"];
{
    let robert = vec.get_mut(2).unwrap();
    assert_eq!(&mut "Robert", robert);
    *robert = "Bjarne";
}
assert_eq!(vector!["Joe", "Mike", "Bjarne"], vec);

pub fn front(&self) -> Option<&A>

Get the first element of a vector.

If the vector is empty, None is returned.

Time: O(log n)

pub fn front_mut(&mut self) -> Option<&mut A>

Get a mutable reference to the first element of a vector.

If the vector is empty, None is returned.

Time: O(log n)

pub fn head(&self) -> Option<&A>

Get the first element of a vector.

If the vector is empty, None is returned.

This is an alias for the front method.

Time: O(log n)

pub fn back(&self) -> Option<&A>

Get the last element of a vector.

If the vector is empty, None is returned.

Time: O(log n)

pub fn back_mut(&mut self) -> Option<&mut A>

Get a mutable reference to the last element of a vector.

If the vector is empty, None is returned.

Time: O(log n)

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

Get the last element of a vector.

If the vector is empty, None is returned.

This is an alias for the back method.

Time: O(log n)

pub fn index_of(&self, value: &A) -> Option<usize>

where A: PartialEq,

Get the index of a given element in the vector.

Searches the vector for the first occurrence of a given value, and returns the index of the value if it’s there. Otherwise, it returns None.

Time: O(n)

Examples

let mut vec = vector![1, 2, 3, 4, 5];
assert_eq!(Some(2), vec.index_of(&3));
assert_eq!(None, vec.index_of(&31337));

pub fn contains(&self, value: &A) -> bool

where A: PartialEq,

Test if a given element is in the vector.

Searches the vector for the first occurrence of a given value, and returns true if it’s there. If it’s nowhere to be found in the vector, it returns false.

Time: O(n)

Examples

let mut vec = vector![1, 2, 3, 4, 5];
assert_eq!(true, vec.contains(&3));
assert_eq!(false, vec.contains(&31337));

pub fn clear(&mut self)

Discard all elements from the vector.

This leaves you with an empty vector, and all elements that were previously inside it are dropped.

Time: O(n)

pub fn binary_search_by<F>(&self, f: F) -> Result<usize, usize>

where F: FnMut(&A) -> Ordering,

Binary search a sorted vector for a given element using a comparator function.

Assumes the vector has already been sorted using the same comparator function, eg. by using sort_by.

If the value is found, it returns Ok(index) where index is the index of the element. If the value isn’t found, it returns Err(index) where index is the index at which the element would need to be inserted to maintain sorted order.

Time: O(log n)

pub fn binary_search(&self, value: &A) -> Result<usize, usize>

where A: Ord,

Binary search a sorted vector for a given element.

If the value is found, it returns Ok(index) where index is the index of the element. If the value isn’t found, it returns Err(index) where index is the index at which the element would need to be inserted to maintain sorted order.

Time: O(log n)

pub fn binary_search_by_key<B, F>(&self, b: &B, f: F) -> Result<usize, usize>

where F: FnMut(&A) -> B, B: Ord,

Binary search a sorted vector for a given element with a key extract function.

Assumes the vector has already been sorted using the same key extract function, eg. by using sort_by_key.

If the value is found, it returns Ok(index) where index is the index of the element. If the value isn’t found, it returns Err(index) where index is the index at which the element would need to be inserted to maintain sorted order.

Time: O(log n)

impl<A: Clone> Vector<A>

pub fn unit(a: A) -> Self

Construct a vector with a single value.

Examples

let vec = Vector::unit(1337);
assert_eq!(1, vec.len());
assert_eq!(
  vec.get(0),
  Some(&1337)
);

pub fn update(&self, index: usize, value: A) -> Self

Create a new vector with the value at index index updated.

Panics if the index is out of bounds.

Time: O(log n)

Examples

let mut vec = vector![1, 2, 3];
assert_eq!(vector![1, 5, 3], vec.update(1, 5));

pub fn set(&mut self, index: usize, value: A) -> A

Update the value at index index in a vector.

Returns the previous value at the index.

Panics if the index is out of bounds.

Time: O(log n)

pub fn swap(&mut self, i: usize, j: usize)

Swap the elements at indices i and j.

Time: O(log n)

pub fn push_front(&mut self, value: A)

Push a value to the front of a vector.

Time: O(1)*

Examples

let mut vec = vector![5, 6, 7];
vec.push_front(4);
assert_eq!(vector![4, 5, 6, 7], vec);

pub fn push_back(&mut self, value: A)

Push a value to the back of a vector.

Time: O(1)*

Examples

let mut vec = vector![1, 2, 3];
vec.push_back(4);
assert_eq!(vector![1, 2, 3, 4], vec);

pub fn pop_front(&mut self) -> Option<A>

Remove the first element from a vector and return it.

Time: O(1)*

Examples

let mut vec = vector![1, 2, 3];
assert_eq!(Some(1), vec.pop_front());
assert_eq!(vector![2, 3], vec);

pub fn pop_back(&mut self) -> Option<A>

Remove the last element from a vector and return it.

Time: O(1)*

Examples

let mut vec = vector![1, 2, 3];
assert_eq!(Some(3), vec.pop_back());
assert_eq!(vector![1, 2], vec);

pub fn append(&mut self, other: Self)

Append the vector other to the end of the current vector.

Time: O(log n)

Examples

let mut vec = vector![1, 2, 3];
vec.append(vector![7, 8, 9]);
assert_eq!(vector![1, 2, 3, 7, 8, 9], vec);

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&A) -> bool,

Retain only the elements specified by the predicate.

Remove all elements for which the provided function f returns false from the vector.

Time: O(n)

pub fn split_at(self, index: usize) -> (Self, Self)

Split a vector at a given index.

Split a vector at a given index, consuming the vector and returning a pair of the left hand side and the right hand side of the split.

Time: O(log n)

Examples

let mut vec = vector![1, 2, 3, 7, 8, 9];
let (left, right) = vec.split_at(3);
assert_eq!(vector![1, 2, 3], left);
assert_eq!(vector![7, 8, 9], right);

pub fn split_off(&mut self, index: usize) -> Self

Split a vector at a given index.

Split a vector at a given index, leaving the left hand side in the current vector and returning a new vector containing the right hand side.

Time: O(log n)

Examples

let mut left = vector![1, 2, 3, 7, 8, 9];
let right = left.split_off(3);
assert_eq!(vector![1, 2, 3], left);
assert_eq!(vector![7, 8, 9], right);

pub fn skip(&self, count: usize) -> Self

Construct a vector with count elements removed from the start of the current vector.

Time: O(log n)

pub fn take(&self, count: usize) -> Self

Construct a vector of the first count elements from the current vector.

Time: O(log n)

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

Truncate a vector to the given size.

Discards all elements in the vector beyond the given length.

Panics if the new length is greater than the current length.

Time: O(log n)

pub fn slice<R>(&mut self, range: R) -> Self

where R: RangeBounds<usize>,

Extract a slice from a vector.

Remove the elements from start_index until end_index in the current vector and return the removed slice as a new vector.

Time: O(log n)

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

Insert an element into a vector.

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

Performance Note

While push_front and push_back are heavily optimised operations, insert in the middle of a vector requires a split, a push, and an append. Thus, if you want to insert many elements at the same location, instead of inserting them one by one, you should rather create a new vector containing the elements to insert, split the vector at the insertion point, and append the left hand, the new vector and the right hand in order.

Time: O(log n)

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

Remove an element from a vector.

Remove the element from position ‘index’, shifting all elements after it to the left, and return the removed element.

Performance Note

While pop_front and pop_back are heavily optimised operations, remove in the middle of a vector requires a split, a pop, and an append. Thus, if you want to remove many elements from the same location, instead of removeing them one by one, it is much better to use slice.

Time: O(log n)

pub fn insert_ord(&mut self, item: A)

where A: Ord,

Insert an element into a sorted vector.

Insert an element into a vector in sorted order, assuming the vector is already in sorted order.

Time: O(log n)

Examples

let mut vec = vector![1, 2, 3, 7, 8, 9];
vec.insert_ord(5);
assert_eq!(vector![1, 2, 3, 5, 7, 8, 9], vec);

pub fn sort(&mut self)

where A: Ord,

Sort a vector.

Time: O(n log n)

Examples

let mut vec = vector![3, 2, 5, 4, 1];
vec.sort();
assert_eq!(vector![1, 2, 3, 4, 5], vec);

pub fn sort_by<F>(&mut self, cmp: F)

where F: Fn(&A, &A) -> Ordering,

Sort a vector using a comparator function.

Time: O(n log n)

Examples

let mut vec = vector![3, 2, 5, 4, 1];
vec.sort_by(|left, right| left.cmp(right));
assert_eq!(vector![1, 2, 3, 4, 5], vec);

Trait Implementations

impl<'a, A: Clone> Add for &'a Vector<A>

fn add(self, other: Self) -> Self::Output

Concatenate two vectors.

Time: O(log n)

type Output = Vector<A>

The resulting type after applying the + operator.

impl<A: Clone> Add for Vector<A>

fn add(self, other: Self) -> Self::Output

Concatenate two vectors.

Time: O(log n)

type Output = Vector<A>

The resulting type after applying the + operator.

impl<A: Clone> Clone for Vector<A>

fn clone(&self) -> Self

Clone a vector.

Time: O(1), or O(n) with a very small, bounded n for an inline vector.

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

Performs copy-assignment from source.

impl<A: Clone + Debug> Debug for Vector<A>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<A: Clone> Default for Vector<A>

fn default() -> Self

Returns the “default value” for a type.

impl<A: Clone> Extend<A> for Vector<A>

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

where I: IntoIterator<Item = A>,

Add values to the end of a vector by consuming an iterator.

Time: O(n)

fn extend_one(&mut self, item: A)

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

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

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

Reserves capacity in a collection for the given number of additional elements.

impl<'a, A: Clone> From<&'a [A]> for Vector<A>

fn from(slice: &[A]) -> Self

Converts to this type from the input type.

impl<'a, A: Clone> From<&'a Vec<A>> for Vector<A>

fn from(vec: &Vec<A>) -> Self

Create a vector from a std::vec::Vec.

Time: O(n)

impl<'s, 'a, A, OA> From<&'s Vector<&'a A>> for Vector<OA>

where A: ToOwned<Owned = OA>, OA: Borrow<A> + Clone,

fn from(vec: &Vector<&A>) -> Self

Converts to this type from the input type.

impl<'a, A, S> From<&'a Vector<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(vector: &Vector<A>) -> Self

Converts to this type from the input type.

impl<A: Clone> From<Vec<A>> for Vector<A>

fn from(vec: Vec<A>) -> Self

Create a vector from a std::vec::Vec.

Time: O(n)

impl<A, S> From<Vector<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(vector: Vector<A>) -> Self

Converts to this type from the input type.

impl<A: Clone> FromIterator<A> for Vector<A>

fn from_iter<I>(iter: I) -> Self

where I: IntoIterator<Item = A>,

Create a vector from an iterator.

Time: O(n)

impl<A: Clone + Hash> Hash for Vector<A>

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<A: Clone> Index<usize> for Vector<A>

fn index(&self, index: usize) -> &Self::Output

Get a reference to the value at index index in the vector.

Time: O(log n)

type Output = A

The returned type after indexing.

impl<A: Clone> IndexMut<usize> for Vector<A>

fn index_mut(&mut self, index: usize) -> &mut Self::Output

Get a mutable reference to the value at index index in the vector.

Time: O(log n)

impl<'a, A: Clone> IntoIterator for &'a Vector<A>

type Item = &'a A

The type of the elements being iterated over.

type IntoIter = Iter<'a, A>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<A: Clone> IntoIterator for Vector<A>

type Item = A

The type of the elements being iterated over.

type IntoIter = ConsumingIter<A>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<A: Clone + Ord> Ord for Vector<A>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl<A: Clone + PartialEq> PartialEq for Vector<A>

default fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<A: Clone + Eq> PartialEq for Vector<A>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<A: Clone + PartialOrd> PartialOrd for Vector<A>

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

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

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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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

impl<A: Clone> Sum for Vector<A>

fn sum<I>(it: I) -> Self

where I: Iterator<Item = Self>,

Takes an iterator and generates Self from the elements by “summing up” the items.

impl<A: Clone + Eq> Eq for Vector<A>