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

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);

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);

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

fn reserve(self: &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);

fn try_reserve(self: &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?");

fn shrink_to_fit(self: &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);

fn shrink_to(self: &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);

fn difference<'a>(self: &'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());

fn symmetric_difference<'a>(self: &'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());

fn intersection<'a>(self: &'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());

fn union<'a>(self: &'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());

fn contains<Q>(self: &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);

fn get<Q>(self: &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);

fn get_or_insert(self: &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

fn get_or_insert_with<Q, F>(self: &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());

fn entry(self: &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'));

fn is_disjoint(self: &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);

fn is_subset(self: &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);

fn is_superset(self: &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);

fn insert(self: &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);

unsafe fn insert_unique_unchecked(self: &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.

fn replace(self: &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);

fn remove<Q>(self: &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);

fn take<Q>(self: &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);

fn allocation_size(self: &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.

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

fn allocator(self: &Self) -> &A

Returns a reference to the underlying allocator.

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);

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);

fn hasher(self: &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();

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

fn capacity(self: &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);

fn iter(self: &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);
}

fn len(self: &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);

fn is_empty(self: &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());

fn drain(self: &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());

fn retain<F>(self: &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);

fn extract_if<F>(self: &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]);

fn clear(self: &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());

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

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

impl<Q, K> Equivalent for HashSet<T, S, A>

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

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

fn type_id(self: &Self) -> TypeId

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

fn borrow(self: &Self) -> &T

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

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

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

unsafe fn clone_to_uninit(self: &Self, dest: *mut u8)

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

fn from(t: T) -> T

Returns the argument unchanged.

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

fn to_owned(self: &Self) -> T

fn clone_into(self: &Self, target: &mut T)

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

fn bitand_assign(self: &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> BitOrAssign for HashSet<T, S, A>

fn bitor_assign(self: &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, S, A> BitXorAssign for HashSet<T, S, A>

fn bitxor_assign(self: &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> Debug for HashSet<T, S, A>

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

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

fn default() -> Self

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

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

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

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

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

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

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

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

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

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

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

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

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

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

fn sub_assign(self: &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, S, A> Sync for HashSet<T, S, A>

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

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

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

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

fn into_iter(self: 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);
}

impl<T, U> Into for HashSet<T, S, A>

fn into(self: Self) -> U

Calls U::from(self).

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

impl<T, U> TryFrom for HashSet<T, S, A>

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

impl<T, U> TryInto for HashSet<T, S, A>

fn try_into(self: Self) -> Result<U, <U as TryFrom<T>>::Error>

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

fn clone(self: &Self) -> Self

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