hashbrown

Struct HashSet

source
pub struct HashSet<T, S = DefaultHashBuilder, A: Allocator = Global> { /* private fields */ }
Expand description

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§

source§

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

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pub fn par_union<'a>(&'a self, other: &'a Self) -> ParUnion<'a, T, S, A>

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

source

pub fn par_difference<'a>( &'a self, other: &'a Self, ) -> ParDifference<'a, T, S, A>

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

source

pub fn par_symmetric_difference<'a>( &'a self, other: &'a Self, ) -> ParSymmetricDifference<'a, T, S, A>

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

source

pub fn par_intersection<'a>( &'a self, other: &'a Self, ) -> ParIntersection<'a, T, S, A>

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

source

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

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

This method runs in a potentially parallel fashion.

source

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

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

This method runs in a potentially parallel fashion.

source

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

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

This method runs in a potentially parallel fashion.

source

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

Returns true if the set is equal to another, i.e. both sets contain the same values.

This method runs in a potentially parallel fashion.

source§

impl<T, S, A> HashSet<T, S, A>
where T: Eq + Hash + Send, A: Allocator + Send,

source

pub fn par_drain(&mut self) -> ParDrain<'_, T, A>

Consumes (potentially in parallel) all values in an arbitrary order, while preserving the set’s allocated memory for reuse.

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impl<T> HashSet<T, DefaultHashBuilder>

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pub fn new() -> Self

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();
source

pub fn with_capacity(capacity: usize) -> Self

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);
source§

impl<T: Hash + Eq, A: Allocator> HashSet<T, DefaultHashBuilder, A>

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pub fn new_in(alloc: A) -> Self

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();
source

pub fn with_capacity_in(capacity: usize, alloc: A) -> Self

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);
source§

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

source

pub fn capacity(&self) -> usize

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);
source

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

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);
}
source

pub fn len(&self) -> usize

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);
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pub fn is_empty(&self) -> bool

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());
source

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

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

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

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]);
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pub fn clear(&mut self)

Clears the set, removing all values.

§Examples
use hashbrown::HashSet;

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

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

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pub const fn with_hasher(hasher: S) -> Self

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);
source

pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> Self

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);
source§

impl<T, S, A> HashSet<T, S, A>
where A: Allocator,

source

pub fn allocator(&self) -> &A

Returns a reference to the underlying allocator.

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pub const fn with_hasher_in(hasher: S, alloc: A) -> Self

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);
source

pub fn with_capacity_and_hasher_in(capacity: usize, hasher: S, alloc: A) -> Self

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);
source

pub fn hasher(&self) -> &S

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();
source§

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

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

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

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?");
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pub fn shrink_to_fit(&mut self)

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

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

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

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

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());
source

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

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());
source

pub fn contains<Q>(&self, value: &Q) -> bool
where Q: Hash + Equivalent<T> + ?Sized,

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);
source

pub fn get<Q>(&self, value: &Q) -> Option<&T>
where Q: Hash + Equivalent<T> + ?Sized,

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

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
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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,

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

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'));
source

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

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);
source

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

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);
source

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

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);
source

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

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);
source

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

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.

source

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

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);
source

pub fn remove<Q>(&mut self, value: &Q) -> bool
where Q: Hash + Equivalent<T> + ?Sized,

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);
source

pub fn take<Q>(&mut self, value: &Q) -> Option<T>
where Q: Hash + Equivalent<T> + ?Sized,

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);
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pub fn allocation_size(&self) -> usize

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§

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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,

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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());
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type Output = HashSet<T, S, A>

The resulting type after applying the & operator.
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impl<T, S, A> BitAndAssign<&HashSet<T, S, A>> for HashSet<T, S, A>
where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

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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());
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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,

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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());
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type Output = HashSet<T, S, A>

The resulting type after applying the | operator.
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impl<T, S, A> BitOrAssign<&HashSet<T, S, A>> for HashSet<T, S, A>
where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

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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());
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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,

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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());
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type Output = HashSet<T, S, A>

The resulting type after applying the ^ operator.
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impl<T, S, A> BitXorAssign<&HashSet<T, S, A>> for HashSet<T, S, A>
where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

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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());
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impl<T: Clone, S: Clone, A: Allocator + Clone> Clone for HashSet<T, S, A>

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fn clone(&self) -> Self

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<T, S, A> Debug for HashSet<T, S, A>
where T: Debug, A: Allocator,

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

Formats the value using the given formatter. Read more
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impl<T, S, A> Default for HashSet<T, S, A>
where S: Default, A: Default + Allocator,

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fn default() -> Self

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

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impl<'de, T, S, A> Deserialize<'de> for HashSet<T, S, A>
where T: Deserialize<'de> + Eq + Hash, S: BuildHasher + Default, A: Allocator + Default,

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fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more
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impl<'a, T, S, A> Extend<&'a T> for HashSet<T, S, A>
where T: 'a + Eq + Hash + Copy, S: BuildHasher, A: Allocator,

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fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I)

Extends a collection with the contents of an iterator. Read more
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fn extend_one(&mut self, k: &'a T)

🔬This is a nightly-only experimental API. (extend_one)
Extends a collection with exactly one element.
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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. Read more
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impl<T, S, A> Extend<T> for HashSet<T, S, A>
where T: Eq + Hash, S: BuildHasher, A: Allocator,

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

Extends a collection with the contents of an iterator. Read more
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fn extend_one(&mut self, k: T)

🔬This is a nightly-only experimental API. (extend_one)
Extends a collection with exactly one element.
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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. Read more
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impl<T, A, const N: usize> From<[T; N]> for HashSet<T, DefaultHashBuilder, A>
where T: Eq + Hash, A: Default + Allocator,

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fn from(arr: [T; N]) -> Self

§Examples
use hashbrown::HashSet;

let set1 = HashSet::from([1, 2, 3, 4]);
let set2: HashSet<_> = [1, 2, 3, 4].into();
assert_eq!(set1, set2);
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impl<T, S, A> From<HashMap<T, (), S, A>> for HashSet<T, S, A>
where A: Allocator,

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

Converts to this type from the input type.
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impl<T, S, A> FromIterator<T> for HashSet<T, S, A>
where T: Eq + Hash, S: BuildHasher + Default, A: Default + Allocator,

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fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self

Creates a value from an iterator. Read more
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impl<T, S> FromParallelIterator<T> for HashSet<T, S, Global>
where T: Eq + Hash + Send, S: BuildHasher + Default,

Collect values from a parallel iterator into a hashset.

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fn from_par_iter<P>(par_iter: P) -> Self
where P: IntoParallelIterator<Item = T>,

Creates an instance of the collection from the parallel iterator par_iter. Read more
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impl<'a, T, S, A: Allocator> IntoIterator for &'a HashSet<T, S, A>

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type Item = &'a T

The type of the elements being iterated over.
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type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?
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fn into_iter(self) -> Iter<'a, T>

Creates an iterator from a value. Read more
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impl<T, S, A: Allocator> IntoIterator for HashSet<T, S, A>

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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);
}
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type Item = T

The type of the elements being iterated over.
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type IntoIter = IntoIter<T, A>

Which kind of iterator are we turning this into?
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impl<'a, T: Sync, S, A: Allocator> IntoParallelIterator for &'a HashSet<T, S, A>

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type Item = &'a T

The type of item that the parallel iterator will produce.
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type Iter = ParIter<'a, T>

The parallel iterator type that will be created.
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fn into_par_iter(self) -> Self::Iter

Converts self into a parallel iterator. Read more
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impl<T: Send, S, A: Allocator + Send> IntoParallelIterator for HashSet<T, S, A>

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type Item = T

The type of item that the parallel iterator will produce.
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type Iter = IntoParIter<T, A>

The parallel iterator type that will be created.
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fn into_par_iter(self) -> Self::Iter

Converts self into a parallel iterator. Read more
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impl<'a, T, S> ParallelExtend<&'a T> for HashSet<T, S, Global>
where T: 'a + Copy + Eq + Hash + Sync, S: BuildHasher,

Extend a hash set with copied items from a parallel iterator.

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fn par_extend<I>(&mut self, par_iter: I)
where I: IntoParallelIterator<Item = &'a T>,

Extends an instance of the collection with the elements drawn from the parallel iterator par_iter. Read more
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impl<T, S> ParallelExtend<T> for HashSet<T, S, Global>
where T: Eq + Hash + Send, S: BuildHasher,

Extend a hash set with items from a parallel iterator.

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fn par_extend<I>(&mut self, par_iter: I)
where I: IntoParallelIterator<Item = T>,

Extends an instance of the collection with the elements drawn from the parallel iterator par_iter. Read more
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impl<T, S, A> PartialEq for HashSet<T, S, A>
where T: Eq + Hash, S: BuildHasher, A: Allocator,

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

Tests for self and other values to be equal, and is used by ==.
1.6.0 · source§

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<T, H, A> Serialize for HashSet<T, H, A>
where T: Serialize + Eq + Hash, H: BuildHasher, A: Allocator,

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fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where S: Serializer,

Serialize this value into the given Serde serializer. Read more
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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,

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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());
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type Output = HashSet<T, S, A>

The resulting type after applying the - operator.
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impl<T, S, A> SubAssign<&HashSet<T, S, A>> for HashSet<T, S, A>
where T: Eq + Hash + Clone, S: BuildHasher, A: Allocator,

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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());
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impl<T, S, A> Eq for HashSet<T, S, A>
where T: Eq + Hash, S: BuildHasher, A: Allocator,

Auto Trait Implementations§

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impl<T, S, A> Freeze for HashSet<T, S, A>
where S: Freeze, A: Freeze,

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

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impl<T, S, A> Send for HashSet<T, S, A>
where S: Send, A: Send, T: Send,

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impl<T, S, A> Sync for HashSet<T, S, A>
where S: Sync, A: Sync, T: Sync,

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impl<T, S, A> Unpin for HashSet<T, S, A>
where S: Unpin, A: Unpin, T: Unpin,

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impl<T, S, A> UnwindSafe for HashSet<T, S, A>
where S: UnwindSafe, A: UnwindSafe, T: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoEither for T

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<'data, I> IntoParallelRefIterator<'data> for I
where I: 'data + ?Sized, &'data I: IntoParallelIterator,

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type Iter = <&'data I as IntoParallelIterator>::Iter

The type of the parallel iterator that will be returned.
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type Item = <&'data I as IntoParallelIterator>::Item

The type of item that the parallel iterator will produce. This will typically be an &'data T reference type.
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fn par_iter(&'data self) -> <I as IntoParallelRefIterator<'data>>::Iter

Converts self into a parallel iterator. Read more
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impl<T> Pointable for T

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> DeserializeOwned for T
where T: for<'de> Deserialize<'de>,