Struct im::hashset::HashSet

pub struct HashSet<A, S = RandomState> { /* fields omitted */ }

An unordered set.

An immutable hash set using hash array mapped tries.

Most operations on this set are O(log_x n) for a suitably high x that it should be nearly O(1) for most sets. Because of this, it's a great choice for a generic set as long as you don't mind that values will need to implement Hash and Eq.

Values will have a predictable order based on the hasher being used. Unless otherwise specified, this will be the standard RandomState hasher.

Methods

impl<A> HashSet<A, RandomState>

#[must_use]

pub fn new() -> Self

Construct an empty set.

impl<A> HashSet<A, RandomState> where
    A: Hash + Eq + Clone, 

#[must_use]

pub fn singleton(a: A) -> Self

Deprecated since 12.3.0:

renamed to unit for consistency

Construct a set with a single value.

This method has been deprecated; use unit instead.

#[must_use]

pub fn unit(a: A) -> Self

Construct a set with a single value.

Examples

let set = HashSet::unit(123);
assert!(set.contains(&123));

impl<A, S> HashSet<A, S>

#[must_use]

pub fn is_empty(&self) -> bool

Test whether a set is empty.

Time: O(1)

Examples

assert!(
  !hashset![1, 2, 3].is_empty()
);
assert!(
  HashSet::<i32>::new().is_empty()
);

#[must_use]

pub fn len(&self) -> usize

Get the size of a set.

Time: O(1)

Examples

assert_eq!(3, hashset![1, 2, 3].len());

#[must_use]

pub fn with_hasher<RS>(hasher: RS) -> Self where
    Arc<S>: From<RS>, 

Construct an empty hash set using the provided hasher.

#[must_use]

pub fn hasher(&self) -> &Arc<S>

Get a reference to the set's BuildHasher.

#[must_use]

pub fn new_from<A1>(&self) -> HashSet<A1, S> where
    A1: Hash + Eq + Clone, 

Construct an empty hash set using the same hasher as the current hash set.

pub fn clear(&mut self)

Discard all elements from the set.

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

Time: O(n)

Examples

let mut set = hashset![1, 2, 3];
set.clear();
assert!(set.is_empty());

Important traits for Iter<'a, A>

impl<'a, A> Iterator for Iter<'a, A> where
    A: 'a,  type Item = &'a A;

#[must_use]

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

Get an iterator over the values in a hash set.

Please note that the order is consistent between sets using the same hasher, but no other ordering guarantee is offered. Items will not come out in insertion order or sort order. They will, however, come out in the same order every time for the same set.

impl<A, S> HashSet<A, S> where
    A: Hash + Eq,
    S: BuildHasher, 

#[must_use]

pub fn contains<BA: ?Sized>(&self, a: &BA) -> bool where
    BA: Hash + Eq,
    A: Borrow<BA>, 

Test if a value is part of a set.

Time: O(log n)

#[must_use]

pub fn is_subset<RS>(&self, other: RS) -> bool where
    RS: Borrow<Self>, 

Test whether a set is a subset of another set, meaning that all values in our set must also be in the other set.

Time: O(n log n)

#[must_use]

pub fn is_proper_subset<RS>(&self, other: RS) -> bool where
    RS: Borrow<Self>, 

Test whether a set is a proper subset of another set, meaning that all values in our set must also be in the other set. A proper subset must also be smaller than the other set.

Time: O(n log n)

impl<A, S> HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher, 

Important traits for IterMut<'a, A>

impl<'a, A> Iterator for IterMut<'a, A> where
    A: 'a + Clone,  type Item = &'a mut A;

#[must_use]

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

Get a mutable iterator over the values in a hash set.

Please note that the order is consistent between sets using the same hasher, but no other ordering guarantee is offered. Items will not come out in insertion order or sort order. They will, however, come out in the same order every time for the same set.

pub fn insert(&mut self, a: A) -> Option<A>

Insert a value into a set.

Time: O(log n)

pub fn remove<BA: ?Sized>(&mut self, a: &BA) -> Option<A> where
    BA: Hash + Eq,
    A: Borrow<BA>, 

Remove a value from a set if it exists.

Time: O(log n)

#[must_use]

pub fn update(&self, a: A) -> Self

Construct a new set from the current set with the given value added.

Time: O(log n)

Examples

let set = hashset![123];
assert_eq!(
  set.update(456),
  hashset![123, 456]
);

#[must_use]

pub fn without<BA: ?Sized>(&self, a: &BA) -> Self where
    BA: Hash + Eq,
    A: Borrow<BA>, 

Construct a new set with the given value removed if it's in the set.

Time: O(log n)

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

Filter out values from a set which don't satisfy a predicate.

This is slightly more efficient than filtering using an iterator, in that it doesn't need to rehash the retained values, but it still needs to reconstruct the entire tree structure of the set.

Time: O(n log n)

#[must_use]

pub fn union(self, other: Self) -> Self

Construct the union of two sets.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{1, 2, 3};
assert_eq!(expected, set1.union(set2));

#[must_use]

pub fn unions<I>(i: I) -> Self where
    I: IntoIterator<Item = Self>,
    S: Default, 

Construct the union of multiple sets.

Time: O(n log n)

#[must_use]

pub fn difference(self, other: Self) -> Self

Construct the difference between two sets.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{1, 3};
assert_eq!(expected, set1.difference(set2));

#[must_use]

pub fn intersection(self, other: Self) -> Self

Construct the intersection of two sets.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{2};
assert_eq!(expected, set1.intersection(set2));

Trait Implementations

impl<A, S> PartialOrd<HashSet<A, S>> for HashSet<A, S> where
    A: Hash + Eq + Clone + PartialOrd,
    S: BuildHasher + Default, 

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

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

#[must_use]

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

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

#[must_use]

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

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

#[must_use]

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

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

#[must_use]

default 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, S> Eq for HashSet<A, S> where
    A: Hash + Eq,
    S: BuildHasher + Default, 

impl<A, S> Ord for HashSet<A, S> where
    A: Hash + Eq + Clone + Ord,
    S: BuildHasher + Default, 

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

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

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

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

Restrict a value to a certain interval.

impl<A, S, R> Extend<R> for HashSet<A, S> where
    A: Hash + Eq + Clone + From<R>,
    S: BuildHasher, 

fn extend<I>(&mut self, iter: I) where
    I: IntoIterator<Item = R>, 

Extends a collection with the contents of an iterator.

impl<A, S> Clone for HashSet<A, S> where
    A: Clone, 

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<A, S> PartialEq<HashSet<A, S>> for HashSet<A, S> where
    A: Hash + Eq,
    S: BuildHasher + Default, 

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

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

#[must_use]

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

This method tests for !=.

impl<A, S> Default for HashSet<A, S> where
    S: BuildHasher + Default, 

fn default() -> Self

Returns the "default value" for a type.

impl<'a, A, S> IntoIterator for &'a HashSet<A, S> where
    A: Hash + Eq,
    S: BuildHasher, 

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, S> IntoIterator for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher, 

type Item = A

The type of the elements being iterated over.

type IntoIter = ConsumingIter<Self::Item>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<A: Hash + Eq + Ord + Clone, S: BuildHasher> From<HashSet<A, S>> for OrdSet<A>

fn from(hashset: HashSet<A, S>) -> Self

Performs the conversion.

impl<'a, A: Hash + Eq + Ord + Clone, S: BuildHasher> From<&'a HashSet<A, S>> for OrdSet<A>

fn from(hashset: &HashSet<A, S>) -> Self

Performs the conversion.

impl<'s, 'a, A: ?Sized, OA, SA, SB> From<&'s HashSet<&'a A, SA>> for HashSet<OA, SB> where
    A: ToOwned<Owned = OA> + Hash + Eq,
    OA: Borrow<A> + Hash + Eq + Clone,
    SA: BuildHasher,
    SB: BuildHasher + Default, 

fn from(set: &HashSet<&A, SA>) -> Self

Performs the conversion.

impl<'a, A, S> From<&'a [A]> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher + Default, 

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

Performs the conversion.

impl<A, S> From<Vec<A>> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher + Default, 

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

Performs the conversion.

impl<'a, A, S> From<&'a Vec<A>> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher + Default, 

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

Performs the conversion.

impl<A, S> From<HashSet<A, RandomState>> for HashSet<A, S> where
    A: Eq + Hash + Clone,
    S: BuildHasher + Default, 

fn from(hash_set: HashSet<A>) -> Self

Performs the conversion.

impl<'a, A, S> From<&'a HashSet<A, RandomState>> for HashSet<A, S> where
    A: Eq + Hash + Clone,
    S: BuildHasher + Default, 

fn from(hash_set: &HashSet<A>) -> Self

Performs the conversion.

impl<'a, A, S> From<&'a BTreeSet<A>> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher + Default, 

fn from(btree_set: &BTreeSet<A>) -> Self

Performs the conversion.

impl<A, S> From<OrdSet<A>> for HashSet<A, S> where
    A: Ord + Hash + Eq + Clone,
    S: BuildHasher + Default, 

fn from(ordset: OrdSet<A>) -> Self

Performs the conversion.

impl<'a, A, S> From<&'a OrdSet<A>> for HashSet<A, S> where
    A: Ord + Hash + Eq + Clone,
    S: BuildHasher + Default, 

fn from(ordset: &OrdSet<A>) -> Self

Performs the conversion.

impl<A, S> Hash for HashSet<A, S> where
    A: Hash + Eq,
    S: BuildHasher + Default, 

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

Feeds this value into the given [Hasher].

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

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

impl<A, S> Add<HashSet<A, S>> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher, 

type Output = HashSet<A, S>

The resulting type after applying the + operator.

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

Performs the + operation.

impl<'a, A, S> Add<&'a HashSet<A, S>> for &'a HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher, 

type Output = HashSet<A, S>

The resulting type after applying the + operator.

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

Performs the + operation.

impl<A, S> Mul<HashSet<A, S>> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher, 

type Output = HashSet<A, S>

The resulting type after applying the * operator.

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

Performs the * operation.

impl<'a, A, S> Mul<&'a HashSet<A, S>> for &'a HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher, 

type Output = HashSet<A, S>

The resulting type after applying the * operator.

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

Performs the * operation.

impl<A, RA, S> FromIterator<RA> for HashSet<A, S> where
    A: Hash + Eq + Clone + From<RA>,
    S: BuildHasher + Default, 

fn from_iter<T>(i: T) -> Self where
    T: IntoIterator<Item = RA>, 

Creates a value from an iterator.

impl<A, S> Sum<HashSet<A, S>> for HashSet<A, S> where
    A: Hash + Eq + Clone,
    S: BuildHasher + Default, 

fn sum<I>(it: I) -> Self where
    I: Iterator<Item = Self>, 

Method which takes an iterator and generates Self from the elements by "summing up" the items.

impl<A, S> Debug for HashSet<A, S> where
    A: Hash + Eq + Debug,
    S: BuildHasher, 

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

Formats the value using the given formatter.

impl<A, S> Debug for HashSet<A, S> where
    A: Hash + Eq + Debug + Ord,
    S: BuildHasher, 

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

Formats the value using the given formatter.