Struct HashSet

pub struct HashSet<T, S = RandomState, A = Global>
where
    A: Allocator,
{ /* private fields */ }

Available on crate features dep_hashbrown and alloc only.

A hash set implemented as a HashMap where the value is ().

As with the HashMap type, a HashSet requires that the elements implement the Eq and Hash traits. This can frequently be achieved by using #[derive(PartialEq, Eq, Hash)]. If you implement these yourself, it is important that the following property holds:

k1 == k2 -> hash(k1) == hash(k2)

In other words, if two keys are equal, their hashes must be equal.

It is a logic error for an item to be modified in such a way that the item’s hash, as determined by the Hash trait, or its equality, as determined by the Eq trait, changes while it is in the set. This is normally only possible through Cell, RefCell, global state, I/O, or unsafe code.

It is also a logic error for the Hash implementation of a key to panic. This is generally only possible if the trait is implemented manually. If a panic does occur then the contents of the HashSet may become corrupted and some items may be dropped from the table.

Examples

use hashbrown::HashSet;
// Type inference lets us omit an explicit type signature (which
// would be `HashSet<String>` in this example).
let mut books = HashSet::new();

// Add some books.
books.insert("A Dance With Dragons".to_string());
books.insert("To Kill a Mockingbird".to_string());
books.insert("The Odyssey".to_string());
books.insert("The Great Gatsby".to_string());

// Check for a specific one.
if !books.contains("The Winds of Winter") {
    println!("We have {} books, but The Winds of Winter ain't one.",
             books.len());
}

// Remove a book.
books.remove("The Odyssey");

// Iterate over everything.
for book in &books {
    println!("{}", book);
}

The easiest way to use HashSet with a custom type is to derive Eq and Hash. We must also derive PartialEq. This will in the future be implied by Eq.

use hashbrown::HashSet;
#[derive(Hash, Eq, PartialEq, Debug)]
struct Viking {
    name: String,
    power: usize,
}

let mut vikings = HashSet::new();

vikings.insert(Viking { name: "Einar".to_string(), power: 9 });
vikings.insert(Viking { name: "Einar".to_string(), power: 9 });
vikings.insert(Viking { name: "Olaf".to_string(), power: 4 });
vikings.insert(Viking { name: "Harald".to_string(), power: 8 });

// Use derived implementation to print the vikings.
for x in &vikings {
    println!("{:?}", x);
}

A HashSet with fixed list of elements can be initialized from an array:

use hashbrown::HashSet;

let viking_names: HashSet<&'static str> =
    [ "Einar", "Olaf", "Harald" ].into_iter().collect();
// use the values stored in the set

Implementations

impl<T> HashSet<T>

pub fn new() -> HashSet<T>

Available on crate features dep_hashbrown or std only.

Creates an empty HashSet.

The hash set is initially created with a capacity of 0, so it will not allocate until it is first inserted into.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet, for example with with_hasher method.

Examples

use hashbrown::HashSet;
let set: HashSet<i32> = HashSet::new();

pub fn with_capacity(capacity: usize) -> HashSet<T>

Available on crate features dep_hashbrown or std only.

Creates an empty HashSet with the specified capacity.

The hash set will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash set will not allocate.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet, for example with with_capacity_and_hasher method.

Examples

use hashbrown::HashSet;
let set: HashSet<i32> = HashSet::with_capacity(10);
assert!(set.capacity() >= 10);

impl<T, A> HashSet<T, RandomState, A>

where T: Hash + Eq, A: Allocator,

pub fn new_in(alloc: A) -> HashSet<T, RandomState, A>

Available on crate features dep_hashbrown or std only.

Creates an empty HashSet.

The hash set is initially created with a capacity of 0, so it will not allocate until it is first inserted into.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet, for example with with_hasher_in method.

Examples

use hashbrown::HashSet;
let set: HashSet<i32> = HashSet::new();

pub fn with_capacity_in(capacity: usize, alloc: A) -> HashSet<T, RandomState, A>

Available on crate features dep_hashbrown or std only.

Creates an empty HashSet with the specified capacity.

The hash set will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash set will not allocate.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet, for example with with_capacity_and_hasher_in method.

Examples

use hashbrown::HashSet;
let set: HashSet<i32> = HashSet::with_capacity(10);
assert!(set.capacity() >= 10);

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

where A: Allocator,

pub fn capacity(&self) -> usize

Available on crate features dep_hashbrown or std only.

Returns the number of elements the set can hold without reallocating.

Examples

use hashbrown::HashSet;
let set: HashSet<i32> = HashSet::with_capacity(100);
assert!(set.capacity() >= 100);

pub fn iter(&self) -> Iter<'_, T>

Available on crate features dep_hashbrown or std only.

An iterator visiting all elements in arbitrary order. The iterator element type is &'a T.

Examples

use hashbrown::HashSet;
let mut set = HashSet::new();
set.insert("a");
set.insert("b");

// Will print in an arbitrary order.
for x in set.iter() {
    println!("{}", x);
}

pub fn len(&self) -> usize

Available on crate features dep_hashbrown or std only.

Returns the number of elements in the set.

Examples

use hashbrown::HashSet;

let mut v = HashSet::new();
assert_eq!(v.len(), 0);
v.insert(1);
assert_eq!(v.len(), 1);

pub fn is_empty(&self) -> bool

Available on crate features dep_hashbrown or std only.

Returns true if the set contains no elements.

Examples

use hashbrown::HashSet;

let mut v = HashSet::new();
assert!(v.is_empty());
v.insert(1);
assert!(!v.is_empty());

pub fn drain(&mut self) -> Drain<'_, T, A>

Available on crate features dep_hashbrown or std only.

Clears the set, returning all elements in an iterator.

Examples

use hashbrown::HashSet;

let mut set: HashSet<_> = [1, 2, 3].into_iter().collect();
assert!(!set.is_empty());

// print 1, 2, 3 in an arbitrary order
for i in set.drain() {
    println!("{}", i);
}

assert!(set.is_empty());

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

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

Available on crate features dep_hashbrown or std only.

Retains only the elements specified by the predicate.

In other words, remove all elements e such that f(&e) returns false.

Examples

use hashbrown::HashSet;

let xs = [1,2,3,4,5,6];
let mut set: HashSet<i32> = xs.into_iter().collect();
set.retain(|&k| k % 2 == 0);
assert_eq!(set.len(), 3);

pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, T, F, A>

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

Available on crate features dep_hashbrown or std only.

Drains elements which are true under the given predicate, and returns an iterator over the removed items.

In other words, move all elements e such that f(&e) returns true out into another iterator.

If the returned ExtractIf is not exhausted, e.g. because it is dropped without iterating or the iteration short-circuits, then the remaining elements will be retained. Use retain() with a negated predicate if you do not need the returned iterator.

Examples

use hashbrown::HashSet;

let mut set: HashSet<i32> = (0..8).collect();
let drained: HashSet<i32> = set.extract_if(|v| v % 2 == 0).collect();

let mut evens = drained.into_iter().collect::<Vec<_>>();
let mut odds = set.into_iter().collect::<Vec<_>>();
evens.sort();
odds.sort();

assert_eq!(evens, vec![0, 2, 4, 6]);
assert_eq!(odds, vec![1, 3, 5, 7]);

pub fn clear(&mut self)

Available on crate features dep_hashbrown or std only.

Clears the set, removing all values.

Examples

use hashbrown::HashSet;

let mut v = HashSet::new();
v.insert(1);
v.clear();
assert!(v.is_empty());

impl<T, S> HashSet<T, S>

pub const fn with_hasher(hasher: S) -> HashSet<T, S>

Available on crate features dep_hashbrown or std only.

Creates a new empty hash set which will use the given hasher to hash keys.

The hash set is initially created with a capacity of 0, so it will not allocate until it is first inserted into.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet.

The hash_builder passed should implement the BuildHasher trait for the HashSet to be useful, see its documentation for details.

Examples

use hashbrown::HashSet;
use hashbrown::DefaultHashBuilder;

let s = DefaultHashBuilder::default();
let mut set = HashSet::with_hasher(s);
set.insert(2);

pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> HashSet<T, S>

Available on crate features dep_hashbrown or std only.

Creates an empty HashSet with the specified capacity, using hasher to hash the keys.

The hash set will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash set will not allocate.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet.

The hash_builder passed should implement the BuildHasher trait for the HashSet to be useful, see its documentation for details.

Examples

use hashbrown::HashSet;
use hashbrown::DefaultHashBuilder;

let s = DefaultHashBuilder::default();
let mut set = HashSet::with_capacity_and_hasher(10, s);
set.insert(1);

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

where A: Allocator,

pub fn allocator(&self) -> &A

Available on crate features dep_hashbrown or std only.

Returns a reference to the underlying allocator.

pub const fn with_hasher_in(hasher: S, alloc: A) -> HashSet<T, S, A>

Available on crate features dep_hashbrown or std only.

Creates a new empty hash set which will use the given hasher to hash keys.

The hash set is initially created with a capacity of 0, so it will not allocate until it is first inserted into.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet.

The hash_builder passed should implement the BuildHasher trait for the HashSet to be useful, see its documentation for details.

Examples

use hashbrown::HashSet;
use hashbrown::DefaultHashBuilder;

let s = DefaultHashBuilder::default();
let mut set = HashSet::with_hasher(s);
set.insert(2);

pub fn with_capacity_and_hasher_in( capacity: usize, hasher: S, alloc: A, ) -> HashSet<T, S, A>

Available on crate features dep_hashbrown or std only.

Creates an empty HashSet with the specified capacity, using hasher to hash the keys.

The hash set will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash set will not allocate.

HashDoS resistance

The hash_builder normally use a fixed key by default and that does not allow the HashSet to be protected against attacks such as HashDoS. Users who require HashDoS resistance should explicitly use std::collections::hash_map::RandomState as the hasher when creating a HashSet.

The hash_builder passed should implement the BuildHasher trait for the HashSet to be useful, see its documentation for details.

Examples

use hashbrown::HashSet;
use hashbrown::DefaultHashBuilder;

let s = DefaultHashBuilder::default();
let mut set = HashSet::with_capacity_and_hasher(10, s);
set.insert(1);

pub fn hasher(&self) -> &S

Available on crate features dep_hashbrown or std only.

Returns a reference to the set’s BuildHasher.

Examples

use hashbrown::HashSet;
use hashbrown::DefaultHashBuilder;

let hasher = DefaultHashBuilder::default();
let set: HashSet<i32> = HashSet::with_hasher(hasher);
let hasher: &DefaultHashBuilder = set.hasher();

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

where T: Eq + Hash, S: BuildHasher, A: Allocator,

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

Available on crate features dep_hashbrown or std only.

Reserves capacity for at least additional more elements to be inserted in the HashSet. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new capacity exceeds isize::MAX bytes and abort the program in case of allocation error. Use try_reserve instead if you want to handle memory allocation failure.

Examples

use hashbrown::HashSet;
let mut set: HashSet<i32> = HashSet::new();
set.reserve(10);
assert!(set.capacity() >= 10);

pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>

Available on crate features dep_hashbrown or std only.

Tries to reserve capacity for at least additional more elements to be inserted in the given HashSet<K,V>. The collection may reserve more space to avoid frequent reallocations.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

use hashbrown::HashSet;
let mut set: HashSet<i32> = HashSet::new();
set.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");

pub fn shrink_to_fit(&mut self)

Available on crate features dep_hashbrown or std only.

Shrinks the capacity of the set as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Examples

use hashbrown::HashSet;

let mut set = HashSet::with_capacity(100);
set.insert(1);
set.insert(2);
assert!(set.capacity() >= 100);
set.shrink_to_fit();
assert!(set.capacity() >= 2);

pub fn shrink_to(&mut self, min_capacity: usize)

Available on crate features dep_hashbrown or std only.

Shrinks the capacity of the set with a lower limit. It will drop down no lower than the supplied limit while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Panics if the current capacity is smaller than the supplied minimum capacity.

Examples

use hashbrown::HashSet;

let mut set = HashSet::with_capacity(100);
set.insert(1);
set.insert(2);
assert!(set.capacity() >= 100);
set.shrink_to(10);
assert!(set.capacity() >= 10);
set.shrink_to(0);
assert!(set.capacity() >= 2);

pub fn difference<'a>( &'a self, other: &'a HashSet<T, S, A>, ) -> Difference<'a, T, S, A>

Available on crate features dep_hashbrown or std only.

Visits the values representing the difference, i.e., the values that are in self but not in other.

Examples

use hashbrown::HashSet;
let a: HashSet<_> = [1, 2, 3].into_iter().collect();
let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();

// Can be seen as `a - b`.
for x in a.difference(&b) {
    println!("{}", x); // Print 1
}

let diff: HashSet<_> = a.difference(&b).collect();
assert_eq!(diff, [1].iter().collect());

// Note that difference is not symmetric,
// and `b - a` means something else:
let diff: HashSet<_> = b.difference(&a).collect();
assert_eq!(diff, [4].iter().collect());

pub fn symmetric_difference<'a>( &'a self, other: &'a HashSet<T, S, A>, ) -> SymmetricDifference<'a, T, S, A>

Available on crate features dep_hashbrown or std only.

Visits the values representing the symmetric difference, i.e., the values that are in self or in other but not in both.

Examples

use hashbrown::HashSet;
let a: HashSet<_> = [1, 2, 3].into_iter().collect();
let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();

// Print 1, 4 in arbitrary order.
for x in a.symmetric_difference(&b) {
    println!("{}", x);
}

let diff1: HashSet<_> = a.symmetric_difference(&b).collect();
let diff2: HashSet<_> = b.symmetric_difference(&a).collect();

assert_eq!(diff1, diff2);
assert_eq!(diff1, [1, 4].iter().collect());

pub fn intersection<'a>( &'a self, other: &'a HashSet<T, S, A>, ) -> Intersection<'a, T, S, A>

Available on crate features dep_hashbrown or std only.

Visits the values representing the intersection, i.e., the values that are both in self and other.

Examples

use hashbrown::HashSet;
let a: HashSet<_> = [1, 2, 3].into_iter().collect();
let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();

// Print 2, 3 in arbitrary order.
for x in a.intersection(&b) {
    println!("{}", x);
}

let intersection: HashSet<_> = a.intersection(&b).collect();
assert_eq!(intersection, [2, 3].iter().collect());

pub fn union<'a>(&'a self, other: &'a HashSet<T, S, A>) -> Union<'a, T, S, A>

Available on crate features dep_hashbrown or std only.

Visits the values representing the union, i.e., all the values in self or other, without duplicates.

Examples

use hashbrown::HashSet;
let a: HashSet<_> = [1, 2, 3].into_iter().collect();
let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();

// Print 1, 2, 3, 4 in arbitrary order.
for x in a.union(&b) {
    println!("{}", x);
}

let union: HashSet<_> = a.union(&b).collect();
assert_eq!(union, [1, 2, 3, 4].iter().collect());

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

where Q: Hash + Equivalent<T> + ?Sized,

Available on crate features dep_hashbrown or std only.

Returns true if the set contains a value.

The value may be any borrowed form of the set’s value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use hashbrown::HashSet;

let set: HashSet<_> = [1, 2, 3].into_iter().collect();
assert_eq!(set.contains(&1), true);
assert_eq!(set.contains(&4), false);

pub fn get<Q>(&self, value: &Q) -> Option<&T>

where Q: Hash + Equivalent<T> + ?Sized,

Available on crate features dep_hashbrown or std only.

Returns a reference to the value in the set, if any, that is equal to the given value.

The value may be any borrowed form of the set’s value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use hashbrown::HashSet;

let set: HashSet<_> = [1, 2, 3].into_iter().collect();
assert_eq!(set.get(&2), Some(&2));
assert_eq!(set.get(&4), None);

pub fn get_or_insert(&mut self, value: T) -> &T

Available on crate features dep_hashbrown or std only.

Inserts the given value into the set if it is not present, then returns a reference to the value in the set.

Examples

use hashbrown::HashSet;

let mut set: HashSet<_> = [1, 2, 3].into_iter().collect();
assert_eq!(set.len(), 3);
assert_eq!(set.get_or_insert(2), &2);
assert_eq!(set.get_or_insert(100), &100);
assert_eq!(set.len(), 4); // 100 was inserted

pub fn get_or_insert_with<Q, F>(&mut self, value: &Q, f: F) -> &T

where Q: Hash + Equivalent<T> + ?Sized, F: FnOnce(&Q) -> T,

Available on crate features dep_hashbrown or std only.

Inserts a value computed from f into the set if the given value is not present, then returns a reference to the value in the set.

Examples

use hashbrown::HashSet;

let mut set: HashSet<String> = ["cat", "dog", "horse"]
    .iter().map(|&pet| pet.to_owned()).collect();

assert_eq!(set.len(), 3);
for &pet in &["cat", "dog", "fish"] {
    let value = set.get_or_insert_with(pet, str::to_owned);
    assert_eq!(value, pet);
}
assert_eq!(set.len(), 4); // a new "fish" was inserted

The following example will panic because the new value doesn’t match.

let mut set = hashbrown::HashSet::new();
set.get_or_insert_with("rust", |_| String::new());

pub fn entry(&mut self, value: T) -> Entry<'_, T, S, A>

Available on crate features dep_hashbrown or std only.

Gets the given value’s corresponding entry in the set for in-place manipulation.

Examples

use hashbrown::HashSet;
use hashbrown::hash_set::Entry::*;

let mut singles = HashSet::new();
let mut dupes = HashSet::new();

for ch in "a short treatise on fungi".chars() {
    if let Vacant(dupe_entry) = dupes.entry(ch) {
        // We haven't already seen a duplicate, so
        // check if we've at least seen it once.
        match singles.entry(ch) {
            Vacant(single_entry) => {
                // We found a new character for the first time.
                single_entry.insert();
            }
            Occupied(single_entry) => {
                // We've already seen this once, "move" it to dupes.
                single_entry.remove();
                dupe_entry.insert();
            }
        }
    }
}

assert!(!singles.contains(&'t') && dupes.contains(&'t'));
assert!(singles.contains(&'u') && !dupes.contains(&'u'));
assert!(!singles.contains(&'v') && !dupes.contains(&'v'));

pub fn is_disjoint(&self, other: &HashSet<T, S, A>) -> bool

Available on crate features dep_hashbrown or std only.

Returns true if self has no elements in common with other. This is equivalent to checking for an empty intersection.

Examples

use hashbrown::HashSet;

let a: HashSet<_> = [1, 2, 3].into_iter().collect();
let mut b = HashSet::new();

assert_eq!(a.is_disjoint(&b), true);
b.insert(4);
assert_eq!(a.is_disjoint(&b), true);
b.insert(1);
assert_eq!(a.is_disjoint(&b), false);

pub fn is_subset(&self, other: &HashSet<T, S, A>) -> bool

Available on crate features dep_hashbrown or std only.

Returns true if the set is a subset of another, i.e., other contains at least all the values in self.

Examples

use hashbrown::HashSet;

let sup: HashSet<_> = [1, 2, 3].into_iter().collect();
let mut set = HashSet::new();

assert_eq!(set.is_subset(&sup), true);
set.insert(2);
assert_eq!(set.is_subset(&sup), true);
set.insert(4);
assert_eq!(set.is_subset(&sup), false);

pub fn is_superset(&self, other: &HashSet<T, S, A>) -> bool

Available on crate features dep_hashbrown or std only.

Returns true if the set is a superset of another, i.e., self contains at least all the values in other.

Examples

use hashbrown::HashSet;

let sub: HashSet<_> = [1, 2].into_iter().collect();
let mut set = HashSet::new();

assert_eq!(set.is_superset(&sub), false);

set.insert(0);
set.insert(1);
assert_eq!(set.is_superset(&sub), false);

set.insert(2);
assert_eq!(set.is_superset(&sub), true);

pub fn insert(&mut self, value: T) -> bool

Available on crate features dep_hashbrown or std only.

Adds a value to the set.

If the set did not have this value present, true is returned.

If the set did have this value present, false is returned.

Examples

use hashbrown::HashSet;

let mut set = HashSet::new();

assert_eq!(set.insert(2), true);
assert_eq!(set.insert(2), false);
assert_eq!(set.len(), 1);

pub unsafe fn insert_unique_unchecked(&mut self, value: T) -> &T

Available on crate features dep_hashbrown or std only.

Insert a value the set without checking if the value already exists in the set.

This operation is faster than regular insert, because it does not perform lookup before insertion.

This operation is useful during initial population of the set. For example, when constructing a set from another set, we know that values are unique.

Safety

This operation is safe if a value does not exist in the set.

However, if a value exists in the set already, the behavior is unspecified: this operation may panic, loop forever, or any following operation with the set may panic, loop forever or return arbitrary result.

That said, this operation (and following operations) are guaranteed to not violate memory safety.

However this operation is still unsafe because the resulting HashSet may be passed to unsafe code which does expect the set to behave correctly, and would cause unsoundness as a result.

pub fn replace(&mut self, value: T) -> Option<T>

Available on crate features dep_hashbrown or std only.

Adds a value to the set, replacing the existing value, if any, that is equal to the given one. Returns the replaced value.

Examples

use hashbrown::HashSet;

let mut set = HashSet::new();
set.insert(Vec::<i32>::new());

assert_eq!(set.get(&[][..]).unwrap().capacity(), 0);
set.replace(Vec::with_capacity(10));
assert_eq!(set.get(&[][..]).unwrap().capacity(), 10);

pub fn remove<Q>(&mut self, value: &Q) -> bool

where Q: Hash + Equivalent<T> + ?Sized,

Available on crate features dep_hashbrown or std only.

Removes a value from the set. Returns whether the value was present in the set.

The value may be any borrowed form of the set’s value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use hashbrown::HashSet;

let mut set = HashSet::new();

set.insert(2);
assert_eq!(set.remove(&2), true);
assert_eq!(set.remove(&2), false);

pub fn take<Q>(&mut self, value: &Q) -> Option<T>

where Q: Hash + Equivalent<T> + ?Sized,

Available on crate features dep_hashbrown or std only.

Removes and returns the value in the set, if any, that is equal to the given one.

The value may be any borrowed form of the set’s value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use hashbrown::HashSet;

let mut set: HashSet<_> = [1, 2, 3].into_iter().collect();
assert_eq!(set.take(&2), Some(2));
assert_eq!(set.take(&2), None);

pub fn allocation_size(&self) -> usize

Available on crate features dep_hashbrown or std only.

Returns the total amount of memory allocated internally by the hash set, in bytes.

The returned number is informational only. It is intended to be primarily used for memory profiling.

Trait Implementations

impl<K, S> Archive for HashSet<K, S>

where K: Archive + Hash + Eq, <K as Archive>::Archived: Hash + Eq,

type Archived = ArchivedHashSet<<K as Archive>::Archived>

The archived representation of this type.

type Resolver = HashSetResolver

The resolver for this type. It must contain all the additional information from serializing needed to make the archived type from the normal type.

fn resolve( &self, resolver: <HashSet<K, S> as Archive>::Resolver, out: Place<<HashSet<K, S> as Archive>::Archived>, )

Creates the archived version of this value at the given position and writes it to the given output.

const COPY_OPTIMIZATION: CopyOptimization<Self> = _

An optimization flag that allows the bytes of this type to be copied directly to a writer instead of calling serialize.

impl<T, S, A> BitAnd<&HashSet<T, S, A>> for &HashSet<T, S, A>

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

fn bitand(self, rhs: &HashSet<T, S, A>) -> HashSet<T, S, A>

Returns the intersection of self and rhs as a new HashSet<T, S>.

Examples

use hashbrown::HashSet;

let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![2, 3, 4].into_iter().collect();

let set = &a & &b;

let mut i = 0;
let expected = [2, 3];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

type Output = HashSet<T, S, A>

The resulting type after applying the & operator.

impl<T, S, A> BitAndAssign<&HashSet<T, S, A>> for HashSet<T, S, A>

where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

fn bitand_assign(&mut self, rhs: &HashSet<T, S, A>)

Modifies this set to contain the intersection of self and rhs.

Examples

use hashbrown::HashSet;

let mut a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![2, 3, 4].into_iter().collect();

a &= &b;

let mut i = 0;
let expected = [2, 3];
for x in &a {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<T, S, A> BitOr<&HashSet<T, S, A>> for &HashSet<T, S, A>

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

fn bitor(self, rhs: &HashSet<T, S, A>) -> HashSet<T, S, A>

Returns the union of self and rhs as a new HashSet<T, S>.

Examples

use hashbrown::HashSet;

let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();

let set = &a | &b;

let mut i = 0;
let expected = [1, 2, 3, 4, 5];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

type Output = HashSet<T, S, A>

The resulting type after applying the | operator.

impl<T, S, A> BitOrAssign<&HashSet<T, S, A>> for HashSet<T, S, A>

where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

fn bitor_assign(&mut self, rhs: &HashSet<T, S, A>)

Modifies this set to contain the union of self and rhs.

Examples

use hashbrown::HashSet;

let mut a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();

a |= &b;

let mut i = 0;
let expected = [1, 2, 3, 4, 5];
for x in &a {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<T> BitSized<{$PTR_BITS * 3}> for HashSet<T>

const BIT_SIZE: usize = _

The bit size of this type (only the relevant data part, without padding).

const MIN_BYTE_SIZE: usize = _

The rounded up byte size for this type.

fn bit_size(&self) -> usize

Returns the bit size of this type (only the relevant data part, without padding).

fn min_byte_size(&self) -> usize

Returns the rounded up byte size for this type.

impl<T, S, A> BitXor<&HashSet<T, S, A>> for &HashSet<T, S, A>

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

fn bitxor(self, rhs: &HashSet<T, S, A>) -> HashSet<T, S, A>

Returns the symmetric difference of self and rhs as a new HashSet<T, S>.

Examples

use hashbrown::HashSet;

let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();

let set = &a ^ &b;

let mut i = 0;
let expected = [1, 2, 4, 5];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

type Output = HashSet<T, S, A>

The resulting type after applying the ^ operator.

impl<T, S, A> BitXorAssign<&HashSet<T, S, A>> for HashSet<T, S, A>

where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

fn bitxor_assign(&mut self, rhs: &HashSet<T, S, A>)

Modifies this set to contain the symmetric difference of self and rhs.

Examples

use hashbrown::HashSet;

let mut a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();

a ^= &b;

let mut i = 0;
let expected = [1, 2, 4, 5];
for x in &a {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<T, S, A> Clone for HashSet<T, S, A>

where T: Clone, S: Clone, A: Allocator + Clone,

fn clone(&self) -> HashSet<T, S, A>

Returns a copy of the value.

fn clone_from(&mut self, source: &HashSet<T, S, A>)

Performs copy-assignment from source.

impl<V> DataCollection for HashSet<V>

fn collection_contains( &self, element: Self::Element, ) -> Result<bool, NotAvailable>

where V: PartialEq,

This is less efficent than HashSet::contains for not having Hash and Eq.

fn collection_count( &self, element: &Self::Element, ) -> Result<usize, NotAvailable>

where V: PartialEq,

This is less efficent than HashSet::contains for not having Hash and Eq.

type Element = V

The element type of the collection.

fn collection_capacity(&self) -> Result<usize, NotAvailable>

Returns the reserved capacity for elements in the collection.

fn collection_len(&self) -> Result<usize, NotAvailable>

Returns the current number of elements in the collection.

fn collection_is_empty(&self) -> Result<bool, NotAvailable>

Returns true if the collection is empty, false if it’s not.

fn collection_is_full(&self) -> Result<bool, NotAvailable>

Returns true if the collection is full, false if it’s not.

impl<T, S, A> Debug for HashSet<T, S, A>

where T: Debug, A: Allocator,

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

Formats the value using the given formatter.

impl<T, S, A> Default for HashSet<T, S, A>

where S: Default, A: Default + Allocator,

fn default() -> HashSet<T, S, A>

Creates an empty HashSet<T, S> with the Default value for the hasher.

impl<K, D, S> Deserialize<HashSet<K, S>, D> for ArchivedHashSet<<K as Archive>::Archived>

where K: Archive + Hash + Eq, <K as Archive>::Archived: Deserialize<K, D> + Hash + Eq, D: Fallible + ?Sized, S: Default + BuildHasher,

fn deserialize( &self, deserializer: &mut D, ) -> Result<HashSet<K, S>, <D as Fallible>::Error>

Deserializes using the given deserializer

impl<'a, T, S, A> Extend<&'a T> for HashSet<T, S, A>

where T: 'a + Eq + Hash + Copy, S: BuildHasher, A: Allocator,

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

where I: IntoIterator<Item = &'a T>,

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, k: &'a T)

🔬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<T, S, A> Extend<T> for HashSet<T, S, A>

where T: Eq + Hash, S: BuildHasher, A: Allocator,

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

where I: IntoIterator<Item = T>,

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, k: T)

🔬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<T, A, const N: usize> From<[T; N]> for HashSet<T, RandomState, A>

where T: Eq + Hash, A: Default + Allocator,

fn from(arr: [T; N]) -> HashSet<T, RandomState, A>

Examples

use hashbrown::HashSet;

let set1 = HashSet::from([1, 2, 3, 4]);
let set2: HashSet<_> = [1, 2, 3, 4].into();
assert_eq!(set1, set2);

impl<T, S, A> From<HashMap<T, (), S, A>> for HashSet<T, S, A>

where A: Allocator,

fn from(map: HashMap<T, (), S, A>) -> HashSet<T, S, A>

Converts to this type from the input type.

impl<T, S, A> FromIterator<T> for HashSet<T, S, A>

where T: Eq + Hash, S: BuildHasher + Default, A: Default + Allocator,

fn from_iter<I>(iter: I) -> HashSet<T, S, A>

where I: IntoIterator<Item = T>,

Creates a value from an iterator.

impl<'py, K, S> FromPyObject<'py> for HashSet<K, S>

where K: FromPyObject<'py> + Eq + Hash, S: BuildHasher + Default,

fn extract_bound(ob: &Bound<'py, PyAny>) -> Result<HashSet<K, S>, PyErr>

Extracts Self from the bound smart pointer obj.

impl<'a, T, S, A> IntoIterator for &'a HashSet<T, S, A>

where A: Allocator,

type Item = &'a T

The type of the elements being iterated over.

type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Iter<'a, T>

Creates an iterator from a value.

impl<T, S, A> IntoIterator for HashSet<T, S, A>

where A: Allocator,

fn into_iter(self) -> IntoIter<T, A>

Creates a consuming iterator, that is, one that moves each value out of the set in arbitrary order. The set cannot be used after calling this.

Examples

use hashbrown::HashSet;
let mut set = HashSet::new();
set.insert("a".to_string());
set.insert("b".to_string());

// Not possible to collect to a Vec<String> with a regular `.iter()`.
let v: Vec<String> = set.into_iter().collect();

// Will print in an arbitrary order.
for x in &v {
    println!("{}", x);
}

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T, A>

Which kind of iterator are we turning this into?

impl<K, S> IntoPy<Py<PyAny>> for HashSet<K, S>

where K: IntoPy<Py<PyAny>> + Eq + Hash, S: BuildHasher + Default,

fn into_py(self, py: Python<'_>) -> Py<PyAny>

👎Deprecated since 0.23.0: IntoPy is going to be replaced by IntoPyObject. See the migration guide (https://pyo3.rs/v0.23.0/migration) for more information.

Performs the conversion.

impl<'a, 'py, K, H> IntoPyObject<'py> for &'a HashSet<K, H>

where &'a K: IntoPyObject<'py> + Eq + Hash, H: BuildHasher,

type Target = PySet

The Python output type

type Output = Bound<'py, <&'a HashSet<K, H> as IntoPyObject<'py>>::Target>

The smart pointer type to use.

type Error = PyErr

The type returned in the event of a conversion error.

fn into_pyobject( self, py: Python<'py>, ) -> Result<<&'a HashSet<K, H> as IntoPyObject<'py>>::Output, <&'a HashSet<K, H> as IntoPyObject<'py>>::Error>

Performs the conversion.

impl<'py, K, H> IntoPyObject<'py> for HashSet<K, H>

where K: IntoPyObject<'py> + Eq + Hash, H: BuildHasher,

type Target = PySet

The Python output type

type Output = Bound<'py, <HashSet<K, H> as IntoPyObject<'py>>::Target>

The smart pointer type to use.

type Error = PyErr

The type returned in the event of a conversion error.

fn into_pyobject( self, py: Python<'py>, ) -> Result<<HashSet<K, H> as IntoPyObject<'py>>::Output, <HashSet<K, H> as IntoPyObject<'py>>::Error>

Performs the conversion.

impl<K, AK, S> PartialEq<ArchivedHashSet<AK>> for HashSet<K, S>

where K: Hash + Eq + Borrow<AK>, AK: Hash + Eq, S: BuildHasher,

fn eq(&self, other: &ArchivedHashSet<AK>) -> 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<K, AK, S> PartialEq<HashSet<K, S>> for ArchivedHashSet<AK>

where K: Hash + Eq + Borrow<AK>, AK: Hash + Eq, S: BuildHasher,

fn eq(&self, other: &HashSet<K, S>) -> 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<T, S, A> PartialEq for HashSet<T, S, A>

where T: Eq + Hash, S: BuildHasher, A: Allocator,

fn eq(&self, other: &HashSet<T, S, A>) -> 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<K, S, RS> Serialize<S> for HashSet<K, RS>

where <K as Archive>::Archived: Hash + Eq, K: Serialize<S> + Hash + Eq, S: Fallible + Allocator + Writer + ?Sized, <S as Fallible>::Error: Source,

fn serialize( &self, serializer: &mut S, ) -> Result<<HashSet<K, RS> as Archive>::Resolver, <S as Fallible>::Error>

Writes the dependencies for the object and returns a resolver that can create the archived type.

impl<T, S, A> Sub<&HashSet<T, S, A>> for &HashSet<T, S, A>

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

fn sub(self, rhs: &HashSet<T, S, A>) -> HashSet<T, S, A>

Returns the difference of self and rhs as a new HashSet<T, S>.

Examples

use hashbrown::HashSet;

let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();

let set = &a - &b;

let mut i = 0;
let expected = [1, 2];
for x in &set {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

type Output = HashSet<T, S, A>

The resulting type after applying the - operator.

impl<T, S, A> SubAssign<&HashSet<T, S, A>> for HashSet<T, S, A>

where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

fn sub_assign(&mut self, rhs: &HashSet<T, S, A>)

Modifies this set to contain the difference of self and rhs.

Examples

use hashbrown::HashSet;

let mut a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();

a -= &b;

let mut i = 0;
let expected = [1, 2];
for x in &a {
    assert!(expected.contains(x));
    i += 1;
}
assert_eq!(i, expected.len());

impl<T> ToPyObject for HashSet<T>

where T: Hash + Eq + ToPyObject,

fn to_object(&self, py: Python<'_>) -> Py<PyAny>

👎Deprecated since 0.23.0: ToPyObject is going to be replaced by IntoPyObject. See the migration guide (https://pyo3.rs/v0.23.0/migration) for more information.

Converts self into a Python object.

impl<T, S, A> Eq for HashSet<T, S, A>

where T: Eq + Hash, S: BuildHasher, A: Allocator,