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#[cfg(test)]
mod tests;
use hashbrown::hash_set as base;
use crate::borrow::Borrow;
use crate::collections::TryReserveError;
use crate::fmt;
use crate::hash::{BuildHasher, Hash, RandomState};
use crate::iter::{Chain, FusedIterator};
use crate::ops::{BitAnd, BitOr, BitXor, Sub};
use super::map::map_try_reserve_error;
/// 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:
///
/// ```text
/// k1 == k2 -> hash(k1) == hash(k2)
/// ```
///
/// In other words, if two keys are equal, their hashes must be equal.
/// Violating this property is a logic error.
///
/// It is also a logic error for a key to be modified in such a way that the key's
/// hash, as determined by the [`Hash`] trait, or its equality, as determined by
/// the [`Eq`] trait, changes while it is in the map. This is normally only
/// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
///
/// The behavior resulting from either logic error is not specified, but will
/// be encapsulated to the `HashSet` that observed the logic error and not
/// result in undefined behavior. This could include panics, incorrect results,
/// aborts, memory leaks, and non-termination.
///
/// # Examples
///
/// ```
/// use std::collections::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`],
/// which is required if [`Eq`] is derived.
///
/// ```
/// use std::collections::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 a known list of items can be initialized from an array:
///
/// ```
/// use std::collections::HashSet;
///
/// let viking_names = HashSet::from(["Einar", "Olaf", "Harald"]);
/// ```
///
/// [hash set]: crate::collections#use-the-set-variant-of-any-of-these-maps-when
/// [`HashMap`]: crate::collections::HashMap
/// [`RefCell`]: crate::cell::RefCell
/// [`Cell`]: crate::cell::Cell
#[cfg_attr(not(test), rustc_diagnostic_item = "HashSet")]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct HashSet<T, S = RandomState> {
base: base::HashSet<T, S>,
}
impl<T> HashSet<T, RandomState> {
/// 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.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let set: HashSet<i32> = HashSet::new();
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new() -> HashSet<T, RandomState> {
Default::default()
}
/// Creates an empty `HashSet` with at least the specified capacity.
///
/// The hash set will be able to hold at least `capacity` elements without
/// reallocating. This method is allowed to allocate for more elements than
/// `capacity`. If `capacity` is 0, the hash set will not allocate.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let set: HashSet<i32> = HashSet::with_capacity(10);
/// assert!(set.capacity() >= 10);
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn with_capacity(capacity: usize) -> HashSet<T, RandomState> {
HashSet::with_capacity_and_hasher(capacity, Default::default())
}
}
impl<T, S> HashSet<T, S> {
/// Returns the number of elements the set can hold without reallocating.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let set: HashSet<i32> = HashSet::with_capacity(100);
/// assert!(set.capacity() >= 100);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn capacity(&self) -> usize {
self.base.capacity()
}
/// An iterator visiting all elements in arbitrary order.
/// The iterator element type is `&'a T`.
///
/// # Examples
///
/// ```
/// use std::collections::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}");
/// }
/// ```
///
/// # Performance
///
/// In the current implementation, iterating over set takes O(capacity) time
/// instead of O(len) because it internally visits empty buckets too.
#[inline]
#[rustc_lint_query_instability]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter(&self) -> Iter<'_, T> {
Iter { base: self.base.iter() }
}
/// Returns the number of elements in the set.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut v = HashSet::new();
/// assert_eq!(v.len(), 0);
/// v.insert(1);
/// assert_eq!(v.len(), 1);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn len(&self) -> usize {
self.base.len()
}
/// Returns `true` if the set contains no elements.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut v = HashSet::new();
/// assert!(v.is_empty());
/// v.insert(1);
/// assert!(!v.is_empty());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn is_empty(&self) -> bool {
self.base.is_empty()
}
/// Clears the set, returning all elements as an iterator. Keeps the
/// allocated memory for reuse.
///
/// If the returned iterator is dropped before being fully consumed, it
/// drops the remaining elements. The returned iterator keeps a mutable
/// borrow on the set to optimize its implementation.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut set = HashSet::from([1, 2, 3]);
/// assert!(!set.is_empty());
///
/// // print 1, 2, 3 in an arbitrary order
/// for i in set.drain() {
/// println!("{i}");
/// }
///
/// assert!(set.is_empty());
/// ```
#[inline]
#[rustc_lint_query_instability]
#[stable(feature = "drain", since = "1.6.0")]
pub fn drain(&mut self) -> Drain<'_, T> {
Drain { base: self.base.drain() }
}
/// Creates an iterator which uses a closure to determine if a value should be removed.
///
/// If the closure returns true, then the value is removed and yielded.
/// If the closure returns false, the value will remain in the list and will not be yielded
/// by the 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.
///
/// [`retain`]: HashSet::retain
///
/// # Examples
///
/// Splitting a set into even and odd values, reusing the original set:
///
/// ```
/// #![feature(hash_extract_if)]
/// use std::collections::HashSet;
///
/// let mut set: HashSet<i32> = (0..8).collect();
/// let extracted: HashSet<i32> = set.extract_if(|v| v % 2 == 0).collect();
///
/// let mut evens = extracted.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]);
/// ```
#[inline]
#[rustc_lint_query_instability]
#[unstable(feature = "hash_extract_if", issue = "59618")]
pub fn extract_if<F>(&mut self, pred: F) -> ExtractIf<'_, T, F>
where
F: FnMut(&T) -> bool,
{
ExtractIf { base: self.base.extract_if(pred) }
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` for which `f(&e)` returns `false`.
/// The elements are visited in unsorted (and unspecified) order.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut set = HashSet::from([1, 2, 3, 4, 5, 6]);
/// set.retain(|&k| k % 2 == 0);
/// assert_eq!(set, HashSet::from([2, 4, 6]));
/// ```
///
/// # Performance
///
/// In the current implementation, this operation takes O(capacity) time
/// instead of O(len) because it internally visits empty buckets too.
#[rustc_lint_query_instability]
#[stable(feature = "retain_hash_collection", since = "1.18.0")]
pub fn retain<F>(&mut self, f: F)
where
F: FnMut(&T) -> bool,
{
self.base.retain(f)
}
/// Clears the set, removing all values.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut v = HashSet::new();
/// v.insert(1);
/// v.clear();
/// assert!(v.is_empty());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn clear(&mut self) {
self.base.clear()
}
/// Creates a new empty hash set which will use the given hasher to hash
/// keys.
///
/// The hash set is also created with the default initial capacity.
///
/// Warning: `hasher` is normally randomly generated, and
/// is designed to allow `HashSet`s to be resistant to attacks that
/// cause many collisions and very poor performance. Setting it
/// manually using this function can expose a DoS attack vector.
///
/// The `hash_builder` passed should implement the [`BuildHasher`] trait for
/// the HashMap to be useful, see its documentation for details.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// use std::hash::RandomState;
///
/// let s = RandomState::new();
/// let mut set = HashSet::with_hasher(s);
/// set.insert(2);
/// ```
#[inline]
#[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
#[rustc_const_unstable(feature = "const_collections_with_hasher", issue = "102575")]
pub const fn with_hasher(hasher: S) -> HashSet<T, S> {
HashSet { base: base::HashSet::with_hasher(hasher) }
}
/// Creates an empty `HashSet` with at least the specified capacity, using
/// `hasher` to hash the keys.
///
/// The hash set will be able to hold at least `capacity` elements without
/// reallocating. This method is allowed to allocate for more elements than
/// `capacity`. If `capacity` is 0, the hash set will not allocate.
///
/// Warning: `hasher` is normally randomly generated, and
/// is designed to allow `HashSet`s to be resistant to attacks that
/// cause many collisions and very poor performance. Setting it
/// manually using this function can expose a DoS attack vector.
///
/// The `hash_builder` passed should implement the [`BuildHasher`] trait for
/// the HashMap to be useful, see its documentation for details.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// use std::hash::RandomState;
///
/// let s = RandomState::new();
/// let mut set = HashSet::with_capacity_and_hasher(10, s);
/// set.insert(1);
/// ```
#[inline]
#[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> HashSet<T, S> {
HashSet { base: base::HashSet::with_capacity_and_hasher(capacity, hasher) }
}
/// Returns a reference to the set's [`BuildHasher`].
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// use std::hash::RandomState;
///
/// let hasher = RandomState::new();
/// let set: HashSet<i32> = HashSet::with_hasher(hasher);
/// let hasher: &RandomState = set.hasher();
/// ```
#[inline]
#[stable(feature = "hashmap_public_hasher", since = "1.9.0")]
pub fn hasher(&self) -> &S {
self.base.hasher()
}
}
impl<T, S> HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
/// Reserves capacity for at least `additional` more elements to be inserted
/// in the `HashSet`. The collection may reserve more space to speculatively
/// avoid frequent reallocations. After calling `reserve`,
/// capacity will be greater than or equal to `self.len() + additional`.
/// Does nothing if capacity is already sufficient.
///
/// # Panics
///
/// Panics if the new allocation size overflows `usize`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let mut set: HashSet<i32> = HashSet::new();
/// set.reserve(10);
/// assert!(set.capacity() >= 10);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn reserve(&mut self, additional: usize) {
self.base.reserve(additional)
}
/// Tries to reserve capacity for at least `additional` more elements to be inserted
/// in the `HashSet`. The collection may reserve more space to speculatively
/// avoid frequent reallocations. After calling `try_reserve`,
/// capacity will be greater than or equal to `self.len() + additional` if
/// it returns `Ok(())`.
/// Does nothing if capacity is already sufficient.
///
/// # Errors
///
/// If the capacity overflows, or the allocator reports a failure, then an error
/// is returned.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let mut set: HashSet<i32> = HashSet::new();
/// set.try_reserve(10).expect("why is the test harness OOMing on a handful of bytes?");
/// ```
#[inline]
#[stable(feature = "try_reserve", since = "1.57.0")]
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
self.base.try_reserve(additional).map_err(map_try_reserve_error)
}
/// 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 std::collections::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);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn shrink_to_fit(&mut self) {
self.base.shrink_to_fit()
}
/// 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.
///
/// If the current capacity is less than the lower limit, this is a no-op.
/// # Examples
///
/// ```
/// use std::collections::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);
/// ```
#[inline]
#[stable(feature = "shrink_to", since = "1.56.0")]
pub fn shrink_to(&mut self, min_capacity: usize) {
self.base.shrink_to(min_capacity)
}
/// Visits the values representing the difference,
/// i.e., the values that are in `self` but not in `other`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// // 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());
/// ```
#[inline]
#[rustc_lint_query_instability]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn difference<'a>(&'a self, other: &'a HashSet<T, S>) -> Difference<'a, T, S> {
Difference { iter: self.iter(), other }
}
/// Visits the values representing the symmetric difference,
/// i.e., the values that are in `self` or in `other` but not in both.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// // 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());
/// ```
#[inline]
#[rustc_lint_query_instability]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn symmetric_difference<'a>(
&'a self,
other: &'a HashSet<T, S>,
) -> SymmetricDifference<'a, T, S> {
SymmetricDifference { iter: self.difference(other).chain(other.difference(self)) }
}
/// Visits the values representing the intersection,
/// i.e., the values that are both in `self` and `other`.
///
/// When an equal element is present in `self` and `other`
/// then the resulting `Intersection` may yield references to
/// one or the other. This can be relevant if `T` contains fields which
/// are not compared by its `Eq` implementation, and may hold different
/// value between the two equal copies of `T` in the two sets.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// // 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());
/// ```
#[inline]
#[rustc_lint_query_instability]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn intersection<'a>(&'a self, other: &'a HashSet<T, S>) -> Intersection<'a, T, S> {
if self.len() <= other.len() {
Intersection { iter: self.iter(), other }
} else {
Intersection { iter: other.iter(), other: self }
}
}
/// Visits the values representing the union,
/// i.e., all the values in `self` or `other`, without duplicates.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// // 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());
/// ```
#[inline]
#[rustc_lint_query_instability]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn union<'a>(&'a self, other: &'a HashSet<T, S>) -> Union<'a, T, S> {
if self.len() >= other.len() {
Union { iter: self.iter().chain(other.difference(self)) }
} else {
Union { iter: other.iter().chain(self.difference(other)) }
}
}
/// 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 std::collections::HashSet;
///
/// let set = HashSet::from([1, 2, 3]);
/// assert_eq!(set.contains(&1), true);
/// assert_eq!(set.contains(&4), false);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool
where
T: Borrow<Q>,
Q: Hash + Eq,
{
self.base.contains(value)
}
/// 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 std::collections::HashSet;
///
/// let set = HashSet::from([1, 2, 3]);
/// assert_eq!(set.get(&2), Some(&2));
/// assert_eq!(set.get(&4), None);
/// ```
#[inline]
#[stable(feature = "set_recovery", since = "1.9.0")]
pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<&T>
where
T: Borrow<Q>,
Q: Hash + Eq,
{
self.base.get(value)
}
/// Inserts the given `value` into the set if it is not present, then
/// returns a reference to the value in the set.
///
/// # Examples
///
/// ```
/// #![feature(hash_set_entry)]
///
/// use std::collections::HashSet;
///
/// let mut set = HashSet::from([1, 2, 3]);
/// 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
/// ```
#[inline]
#[unstable(feature = "hash_set_entry", issue = "60896")]
pub fn get_or_insert(&mut self, value: T) -> &T {
// Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
// `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`.
self.base.get_or_insert(value)
}
/// Inserts an owned copy of the given `value` into the set if it is not
/// present, then returns a reference to the value in the set.
///
/// # Examples
///
/// ```
/// #![feature(hash_set_entry)]
///
/// use std::collections::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_owned(pet);
/// assert_eq!(value, pet);
/// }
/// assert_eq!(set.len(), 4); // a new "fish" was inserted
/// ```
#[inline]
#[unstable(feature = "hash_set_entry", issue = "60896")]
pub fn get_or_insert_owned<Q: ?Sized>(&mut self, value: &Q) -> &T
where
T: Borrow<Q>,
Q: Hash + Eq + ToOwned<Owned = T>,
{
// Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
// `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`.
self.base.get_or_insert_owned(value)
}
/// 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
///
/// ```
/// #![feature(hash_set_entry)]
///
/// use std::collections::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
/// ```
#[inline]
#[unstable(feature = "hash_set_entry", issue = "60896")]
pub fn get_or_insert_with<Q: ?Sized, F>(&mut self, value: &Q, f: F) -> &T
where
T: Borrow<Q>,
Q: Hash + Eq,
F: FnOnce(&Q) -> T,
{
// Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
// `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`.
self.base.get_or_insert_with(value, f)
}
/// Returns `true` if `self` has no elements in common with `other`.
/// This is equivalent to checking for an empty intersection.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// 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);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn is_disjoint(&self, other: &HashSet<T, S>) -> bool {
if self.len() <= other.len() {
self.iter().all(|v| !other.contains(v))
} else {
other.iter().all(|v| !self.contains(v))
}
}
/// Returns `true` if the set is a subset of another,
/// i.e., `other` contains at least all the values in `self`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let sup = HashSet::from([1, 2, 3]);
/// 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);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn is_subset(&self, other: &HashSet<T, S>) -> bool {
if self.len() <= other.len() { self.iter().all(|v| other.contains(v)) } else { false }
}
/// Returns `true` if the set is a superset of another,
/// i.e., `self` contains at least all the values in `other`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let sub = HashSet::from([1, 2]);
/// 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);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn is_superset(&self, other: &HashSet<T, S>) -> bool {
other.is_subset(self)
}
/// Adds a value to the set.
///
/// Returns whether the value was newly inserted. That is:
///
/// - If the set did not previously contain this value, `true` is returned.
/// - If the set already contained this value, `false` is returned,
/// and the set is not modified: original value is not replaced,
/// and the value passed as argument is dropped.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut set = HashSet::new();
///
/// assert_eq!(set.insert(2), true);
/// assert_eq!(set.insert(2), false);
/// assert_eq!(set.len(), 1);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn insert(&mut self, value: T) -> bool {
self.base.insert(value)
}
/// 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 std::collections::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);
/// ```
#[inline]
#[stable(feature = "set_recovery", since = "1.9.0")]
pub fn replace(&mut self, value: T) -> Option<T> {
self.base.replace(value)
}
/// 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 std::collections::HashSet;
///
/// let mut set = HashSet::new();
///
/// set.insert(2);
/// assert_eq!(set.remove(&2), true);
/// assert_eq!(set.remove(&2), false);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
where
T: Borrow<Q>,
Q: Hash + Eq,
{
self.base.remove(value)
}
/// 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 std::collections::HashSet;
///
/// let mut set = HashSet::from([1, 2, 3]);
/// assert_eq!(set.take(&2), Some(2));
/// assert_eq!(set.take(&2), None);
/// ```
#[inline]
#[stable(feature = "set_recovery", since = "1.9.0")]
pub fn take<Q: ?Sized>(&mut self, value: &Q) -> Option<T>
where
T: Borrow<Q>,
Q: Hash + Eq,
{
self.base.take(value)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Clone for HashSet<T, S>
where
T: Clone,
S: Clone,
{
#[inline]
fn clone(&self) -> Self {
Self { base: self.base.clone() }
}
#[inline]
fn clone_from(&mut self, other: &Self) {
self.base.clone_from(&other.base);
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> PartialEq for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
fn eq(&self, other: &HashSet<T, S>) -> bool {
if self.len() != other.len() {
return false;
}
self.iter().all(|key| other.contains(key))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Eq for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> fmt::Debug for HashSet<T, S>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_set().entries(self.iter()).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> FromIterator<T> for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher + Default,
{
#[inline]
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> HashSet<T, S> {
let mut set = HashSet::with_hasher(Default::default());
set.extend(iter);
set
}
}
#[stable(feature = "std_collections_from_array", since = "1.56.0")]
// Note: as what is currently the most convenient built-in way to construct
// a HashSet, a simple usage of this function must not *require* the user
// to provide a type annotation in order to infer the third type parameter
// (the hasher parameter, conventionally "S").
// To that end, this impl is defined using RandomState as the concrete
// type of S, rather than being generic over `S: BuildHasher + Default`.
// It is expected that users who want to specify a hasher will manually use
// `with_capacity_and_hasher`.
// If type parameter defaults worked on impls, and if type parameter
// defaults could be mixed with const generics, then perhaps
// this could be generalized.
// See also the equivalent impl on HashMap.
impl<T, const N: usize> From<[T; N]> for HashSet<T, RandomState>
where
T: Eq + Hash,
{
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let set1 = HashSet::from([1, 2, 3, 4]);
/// let set2: HashSet<_> = [1, 2, 3, 4].into();
/// assert_eq!(set1, set2);
/// ```
fn from(arr: [T; N]) -> Self {
Self::from_iter(arr)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Extend<T> for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
#[inline]
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
self.base.extend(iter);
}
#[inline]
fn extend_one(&mut self, item: T) {
self.base.insert(item);
}
#[inline]
fn extend_reserve(&mut self, additional: usize) {
self.base.extend_reserve(additional);
}
}
#[stable(feature = "hash_extend_copy", since = "1.4.0")]
impl<'a, T, S> Extend<&'a T> for HashSet<T, S>
where
T: 'a + Eq + Hash + Copy,
S: BuildHasher,
{
#[inline]
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
self.extend(iter.into_iter().cloned());
}
#[inline]
fn extend_one(&mut self, &item: &'a T) {
self.base.insert(item);
}
#[inline]
fn extend_reserve(&mut self, additional: usize) {
Extend::<T>::extend_reserve(self, additional)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Default for HashSet<T, S>
where
S: Default,
{
/// Creates an empty `HashSet<T, S>` with the `Default` value for the hasher.
#[inline]
fn default() -> HashSet<T, S> {
HashSet { base: Default::default() }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> BitOr<&HashSet<T, S>> for &HashSet<T, S>
where
T: Eq + Hash + Clone,
S: BuildHasher + Default,
{
type Output = HashSet<T, S>;
/// Returns the union of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// 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());
/// ```
fn bitor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.union(rhs).cloned().collect()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> BitAnd<&HashSet<T, S>> for &HashSet<T, S>
where
T: Eq + Hash + Clone,
S: BuildHasher + Default,
{
type Output = HashSet<T, S>;
/// Returns the intersection of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([2, 3, 4]);
///
/// 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());
/// ```
fn bitand(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.intersection(rhs).cloned().collect()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> BitXor<&HashSet<T, S>> for &HashSet<T, S>
where
T: Eq + Hash + Clone,
S: BuildHasher + Default,
{
type Output = HashSet<T, S>;
/// Returns the symmetric difference of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// 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());
/// ```
fn bitxor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.symmetric_difference(rhs).cloned().collect()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Sub<&HashSet<T, S>> for &HashSet<T, S>
where
T: Eq + Hash + Clone,
S: BuildHasher + Default,
{
type Output = HashSet<T, S>;
/// Returns the difference of `self` and `rhs` as a new `HashSet<T, S>`.
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([3, 4, 5]);
///
/// 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());
/// ```
fn sub(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
self.difference(rhs).cloned().collect()
}
}
/// An iterator over the items of a `HashSet`.
///
/// This `struct` is created by the [`iter`] method on [`HashSet`].
/// See its documentation for more.
///
/// [`iter`]: HashSet::iter
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
///
/// let mut iter = a.iter();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Iter<'a, K: 'a> {
base: base::Iter<'a, K>,
}
/// An owning iterator over the items of a `HashSet`.
///
/// This `struct` is created by the [`into_iter`] method on [`HashSet`]
/// (provided by the [`IntoIterator`] trait). See its documentation for more.
///
/// [`into_iter`]: IntoIterator::into_iter
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
///
/// let mut iter = a.into_iter();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IntoIter<K> {
base: base::IntoIter<K>,
}
/// A draining iterator over the items of a `HashSet`.
///
/// This `struct` is created by the [`drain`] method on [`HashSet`].
/// See its documentation for more.
///
/// [`drain`]: HashSet::drain
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let mut a = HashSet::from([1, 2, 3]);
///
/// let mut drain = a.drain();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Drain<'a, K: 'a> {
base: base::Drain<'a, K>,
}
/// A draining, filtering iterator over the items of a `HashSet`.
///
/// This `struct` is created by the [`extract_if`] method on [`HashSet`].
///
/// [`extract_if`]: HashSet::extract_if
///
/// # Examples
///
/// ```
/// #![feature(hash_extract_if)]
///
/// use std::collections::HashSet;
///
/// let mut a = HashSet::from([1, 2, 3]);
///
/// let mut extract_ifed = a.extract_if(|v| v % 2 == 0);
/// ```
#[unstable(feature = "hash_extract_if", issue = "59618")]
pub struct ExtractIf<'a, K, F>
where
F: FnMut(&K) -> bool,
{
base: base::ExtractIf<'a, K, F>,
}
/// A lazy iterator producing elements in the intersection of `HashSet`s.
///
/// This `struct` is created by the [`intersection`] method on [`HashSet`].
/// See its documentation for more.
///
/// [`intersection`]: HashSet::intersection
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let mut intersection = a.intersection(&b);
/// ```
#[must_use = "this returns the intersection as an iterator, \
without modifying either input set"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Intersection<'a, T: 'a, S: 'a> {
// iterator of the first set
iter: Iter<'a, T>,
// the second set
other: &'a HashSet<T, S>,
}
/// A lazy iterator producing elements in the difference of `HashSet`s.
///
/// This `struct` is created by the [`difference`] method on [`HashSet`].
/// See its documentation for more.
///
/// [`difference`]: HashSet::difference
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let mut difference = a.difference(&b);
/// ```
#[must_use = "this returns the difference as an iterator, \
without modifying either input set"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Difference<'a, T: 'a, S: 'a> {
// iterator of the first set
iter: Iter<'a, T>,
// the second set
other: &'a HashSet<T, S>,
}
/// A lazy iterator producing elements in the symmetric difference of `HashSet`s.
///
/// This `struct` is created by the [`symmetric_difference`] method on
/// [`HashSet`]. See its documentation for more.
///
/// [`symmetric_difference`]: HashSet::symmetric_difference
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let mut intersection = a.symmetric_difference(&b);
/// ```
#[must_use = "this returns the difference as an iterator, \
without modifying either input set"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct SymmetricDifference<'a, T: 'a, S: 'a> {
iter: Chain<Difference<'a, T, S>, Difference<'a, T, S>>,
}
/// A lazy iterator producing elements in the union of `HashSet`s.
///
/// This `struct` is created by the [`union`] method on [`HashSet`].
/// See its documentation for more.
///
/// [`union`]: HashSet::union
///
/// # Examples
///
/// ```
/// use std::collections::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let mut union_iter = a.union(&b);
/// ```
#[must_use = "this returns the union as an iterator, \
without modifying either input set"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Union<'a, T: 'a, S: 'a> {
iter: Chain<Iter<'a, T>, Difference<'a, T, S>>,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, S> IntoIterator for &'a HashSet<T, S> {
type Item = &'a T;
type IntoIter = Iter<'a, T>;
#[inline]
#[rustc_lint_query_instability]
fn into_iter(self) -> Iter<'a, T> {
self.iter()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> IntoIterator for HashSet<T, S> {
type Item = T;
type IntoIter = IntoIter<T>;
/// 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 std::collections::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}");
/// }
/// ```
#[inline]
#[rustc_lint_query_instability]
fn into_iter(self) -> IntoIter<T> {
IntoIter { base: self.base.into_iter() }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K> Clone for Iter<'_, K> {
#[inline]
fn clone(&self) -> Self {
Iter { base: self.base.clone() }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K> Iterator for Iter<'a, K> {
type Item = &'a K;
#[inline]
fn next(&mut self) -> Option<&'a K> {
self.base.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.base.size_hint()
}
#[inline]
fn count(self) -> usize {
self.base.len()
}
#[inline]
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.base.fold(init, f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K> ExactSizeIterator for Iter<'_, K> {
#[inline]
fn len(&self) -> usize {
self.base.len()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K> FusedIterator for Iter<'_, K> {}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<K: fmt::Debug> fmt::Debug for Iter<'_, K> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.clone()).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K> Iterator for IntoIter<K> {
type Item = K;
#[inline]
fn next(&mut self) -> Option<K> {
self.base.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.base.size_hint()
}
#[inline]
fn count(self) -> usize {
self.base.len()
}
#[inline]
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.base.fold(init, f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K> ExactSizeIterator for IntoIter<K> {
#[inline]
fn len(&self) -> usize {
self.base.len()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K> FusedIterator for IntoIter<K> {}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<K: fmt::Debug> fmt::Debug for IntoIter<K> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&self.base, f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K> Iterator for Drain<'a, K> {
type Item = K;
#[inline]
fn next(&mut self) -> Option<K> {
self.base.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.base.size_hint()
}
#[inline]
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.base.fold(init, f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K> ExactSizeIterator for Drain<'_, K> {
#[inline]
fn len(&self) -> usize {
self.base.len()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K> FusedIterator for Drain<'_, K> {}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<K: fmt::Debug> fmt::Debug for Drain<'_, K> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&self.base, f)
}
}
#[unstable(feature = "hash_extract_if", issue = "59618")]
impl<K, F> Iterator for ExtractIf<'_, K, F>
where
F: FnMut(&K) -> bool,
{
type Item = K;
#[inline]
fn next(&mut self) -> Option<K> {
self.base.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.base.size_hint()
}
}
#[unstable(feature = "hash_extract_if", issue = "59618")]
impl<K, F> FusedIterator for ExtractIf<'_, K, F> where F: FnMut(&K) -> bool {}
#[unstable(feature = "hash_extract_if", issue = "59618")]
impl<'a, K, F> fmt::Debug for ExtractIf<'a, K, F>
where
F: FnMut(&K) -> bool,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ExtractIf").finish_non_exhaustive()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Clone for Intersection<'_, T, S> {
#[inline]
fn clone(&self) -> Self {
Intersection { iter: self.iter.clone(), ..*self }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, S> Iterator for Intersection<'a, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Item = &'a T;
#[inline]
fn next(&mut self) -> Option<&'a T> {
loop {
let elt = self.iter.next()?;
if self.other.contains(elt) {
return Some(elt);
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper)
}
#[inline]
fn fold<B, F>(self, init: B, mut f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.iter.fold(init, |acc, elt| if self.other.contains(elt) { f(acc, elt) } else { acc })
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<T, S> fmt::Debug for Intersection<'_, T, S>
where
T: fmt::Debug + Eq + Hash,
S: BuildHasher,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.clone()).finish()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, S> FusedIterator for Intersection<'_, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Clone for Difference<'_, T, S> {
#[inline]
fn clone(&self) -> Self {
Difference { iter: self.iter.clone(), ..*self }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, S> Iterator for Difference<'a, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Item = &'a T;
#[inline]
fn next(&mut self) -> Option<&'a T> {
loop {
let elt = self.iter.next()?;
if !self.other.contains(elt) {
return Some(elt);
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper)
}
#[inline]
fn fold<B, F>(self, init: B, mut f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.iter.fold(init, |acc, elt| if self.other.contains(elt) { acc } else { f(acc, elt) })
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, S> FusedIterator for Difference<'_, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<T, S> fmt::Debug for Difference<'_, T, S>
where
T: fmt::Debug + Eq + Hash,
S: BuildHasher,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.clone()).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Clone for SymmetricDifference<'_, T, S> {
#[inline]
fn clone(&self) -> Self {
SymmetricDifference { iter: self.iter.clone() }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, S> Iterator for SymmetricDifference<'a, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Item = &'a T;
#[inline]
fn next(&mut self) -> Option<&'a T> {
self.iter.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
#[inline]
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.iter.fold(init, f)
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, S> FusedIterator for SymmetricDifference<'_, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<T, S> fmt::Debug for SymmetricDifference<'_, T, S>
where
T: fmt::Debug + Eq + Hash,
S: BuildHasher,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.clone()).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, S> Clone for Union<'_, T, S> {
#[inline]
fn clone(&self) -> Self {
Union { iter: self.iter.clone() }
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, S> FusedIterator for Union<'_, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<T, S> fmt::Debug for Union<'_, T, S>
where
T: fmt::Debug + Eq + Hash,
S: BuildHasher,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.clone()).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, S> Iterator for Union<'a, T, S>
where
T: Eq + Hash,
S: BuildHasher,
{
type Item = &'a T;
#[inline]
fn next(&mut self) -> Option<&'a T> {
self.iter.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
#[inline]
fn count(self) -> usize {
self.iter.count()
}
#[inline]
fn fold<B, F>(self, init: B, f: F) -> B
where
Self: Sized,
F: FnMut(B, Self::Item) -> B,
{
self.iter.fold(init, f)
}
}
#[allow(dead_code)]
fn assert_covariance() {
fn set<'new>(v: HashSet<&'static str>) -> HashSet<&'new str> {
v
}
fn iter<'a, 'new>(v: Iter<'a, &'static str>) -> Iter<'a, &'new str> {
v
}
fn into_iter<'new>(v: IntoIter<&'static str>) -> IntoIter<&'new str> {
v
}
fn difference<'a, 'new>(
v: Difference<'a, &'static str, RandomState>,
) -> Difference<'a, &'new str, RandomState> {
v
}
fn symmetric_difference<'a, 'new>(
v: SymmetricDifference<'a, &'static str, RandomState>,
) -> SymmetricDifference<'a, &'new str, RandomState> {
v
}
fn intersection<'a, 'new>(
v: Intersection<'a, &'static str, RandomState>,
) -> Intersection<'a, &'new str, RandomState> {
v
}
fn union<'a, 'new>(
v: Union<'a, &'static str, RandomState>,
) -> Union<'a, &'new str, RandomState> {
v
}
fn drain<'new>(d: Drain<'static, &'static str>) -> Drain<'new, &'new str> {
d
}
}