1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 use hash::{Hash, BuildHasher};
14 use iter::{Chain, FromIterator, FusedIterator};
15 use ops::{BitOr, BitAnd, BitXor, Sub};
18 use super::map::{self, HashMap, Keys, RandomState};
20 // Future Optimization (FIXME!)
21 // =============================
23 // Iteration over zero sized values is a noop. There is no need
24 // for `bucket.val` in the case of HashSet. I suppose we would need HKT
25 // to get rid of it properly.
27 /// A hash set implemented as a `HashMap` where the value is `()`.
29 /// As with the [`HashMap`] type, a `HashSet` requires that the elements
30 /// implement the [`Eq`] and [`Hash`] traits. This can frequently be achieved by
31 /// using `#[derive(PartialEq, Eq, Hash)]`. If you implement these yourself,
32 /// it is important that the following property holds:
35 /// k1 == k2 -> hash(k1) == hash(k2)
38 /// In other words, if two keys are equal, their hashes must be equal.
41 /// It is a logic error for an item to be modified in such a way that the
42 /// item's hash, as determined by the [`Hash`] trait, or its equality, as
43 /// determined by the [`Eq`] trait, changes while it is in the set. This is
44 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or
50 /// use std::collections::HashSet;
51 /// // Type inference lets us omit an explicit type signature (which
52 /// // would be `HashSet<&str>` in this example).
53 /// let mut books = HashSet::new();
55 /// // Add some books.
56 /// books.insert("A Dance With Dragons");
57 /// books.insert("To Kill a Mockingbird");
58 /// books.insert("The Odyssey");
59 /// books.insert("The Great Gatsby");
61 /// // Check for a specific one.
62 /// if !books.contains("The Winds of Winter") {
63 /// println!("We have {} books, but The Winds of Winter ain't one.",
68 /// books.remove("The Odyssey");
70 /// // Iterate over everything.
71 /// for book in &books {
72 /// println!("{}", book);
76 /// The easiest way to use `HashSet` with a custom type is to derive
77 /// [`Eq`] and [`Hash`]. We must also derive [`PartialEq`], this will in the
78 /// future be implied by [`Eq`].
81 /// use std::collections::HashSet;
82 /// #[derive(Hash, Eq, PartialEq, Debug)]
83 /// struct Viking<'a> {
88 /// let mut vikings = HashSet::new();
90 /// vikings.insert(Viking { name: "Einar", power: 9 });
91 /// vikings.insert(Viking { name: "Einar", power: 9 });
92 /// vikings.insert(Viking { name: "Olaf", power: 4 });
93 /// vikings.insert(Viking { name: "Harald", power: 8 });
95 /// // Use derived implementation to print the vikings.
96 /// for x in &vikings {
97 /// println!("{:?}", x);
101 /// A `HashSet` with fixed list of elements can be initialized from an array:
104 /// use std::collections::HashSet;
107 /// let viking_names: HashSet<&str> =
108 /// [ "Einar", "Olaf", "Harald" ].iter().cloned().collect();
109 /// // use the values stored in the set
113 /// [`Cell`]: ../../std/cell/struct.Cell.html
114 /// [`Eq`]: ../../std/cmp/trait.Eq.html
115 /// [`Hash`]: ../../std/hash/trait.Hash.html
116 /// [`HashMap`]: struct.HashMap.html
117 /// [`PartialEq`]: ../../std/cmp/trait.PartialEq.html
118 /// [`RefCell`]: ../../std/cell/struct.RefCell.html
120 #[stable(feature = "rust1", since = "1.0.0")]
121 pub struct HashSet<T, S = RandomState> {
122 map: HashMap<T, (), S>,
125 impl<T: Hash + Eq> HashSet<T, RandomState> {
126 /// Creates an empty `HashSet`.
128 /// The hash set is initially created with a capacity of 0, so it will not allocate until it
129 /// is first inserted into.
134 /// use std::collections::HashSet;
135 /// let set: HashSet<i32> = HashSet::new();
138 #[stable(feature = "rust1", since = "1.0.0")]
139 pub fn new() -> HashSet<T, RandomState> {
140 HashSet { map: HashMap::new() }
143 /// Creates an empty `HashSet` with the specified capacity.
145 /// The hash set will be able to hold at least `capacity` elements without
146 /// reallocating. If `capacity` is 0, the hash set will not allocate.
151 /// use std::collections::HashSet;
152 /// let set: HashSet<i32> = HashSet::with_capacity(10);
153 /// assert!(set.capacity() >= 10);
156 #[stable(feature = "rust1", since = "1.0.0")]
157 pub fn with_capacity(capacity: usize) -> HashSet<T, RandomState> {
158 HashSet { map: HashMap::with_capacity(capacity) }
162 impl<T, S> HashSet<T, S>
166 /// Creates a new empty hash set which will use the given hasher to hash
169 /// The hash set is also created with the default initial capacity.
171 /// Warning: `hasher` is normally randomly generated, and
172 /// is designed to allow `HashSet`s to be resistant to attacks that
173 /// cause many collisions and very poor performance. Setting it
174 /// manually using this function can expose a DoS attack vector.
179 /// use std::collections::HashSet;
180 /// use std::collections::hash_map::RandomState;
182 /// let s = RandomState::new();
183 /// let mut set = HashSet::with_hasher(s);
187 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
188 pub fn with_hasher(hasher: S) -> HashSet<T, S> {
189 HashSet { map: HashMap::with_hasher(hasher) }
192 /// Creates an empty `HashSet` with with the specified capacity, using
193 /// `hasher` to hash the keys.
195 /// The hash set will be able to hold at least `capacity` elements without
196 /// reallocating. If `capacity` is 0, the hash set will not allocate.
198 /// Warning: `hasher` is normally randomly generated, and
199 /// is designed to allow `HashSet`s to be resistant to attacks that
200 /// cause many collisions and very poor performance. Setting it
201 /// manually using this function can expose a DoS attack vector.
206 /// use std::collections::HashSet;
207 /// use std::collections::hash_map::RandomState;
209 /// let s = RandomState::new();
210 /// let mut set = HashSet::with_capacity_and_hasher(10, s);
214 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
215 pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> HashSet<T, S> {
216 HashSet { map: HashMap::with_capacity_and_hasher(capacity, hasher) }
219 /// Returns a reference to the set's [`BuildHasher`].
221 /// [`BuildHasher`]: ../../std/hash/trait.BuildHasher.html
226 /// use std::collections::HashSet;
227 /// use std::collections::hash_map::RandomState;
229 /// let hasher = RandomState::new();
230 /// let set: HashSet<i32> = HashSet::with_hasher(hasher);
231 /// let hasher: &RandomState = set.hasher();
233 #[stable(feature = "hashmap_public_hasher", since = "1.9.0")]
234 pub fn hasher(&self) -> &S {
238 /// Returns the number of elements the set can hold without reallocating.
243 /// use std::collections::HashSet;
244 /// let set: HashSet<i32> = HashSet::with_capacity(100);
245 /// assert!(set.capacity() >= 100);
248 #[stable(feature = "rust1", since = "1.0.0")]
249 pub fn capacity(&self) -> usize {
253 /// Reserves capacity for at least `additional` more elements to be inserted
254 /// in the `HashSet`. The collection may reserve more space to avoid
255 /// frequent reallocations.
259 /// Panics if the new allocation size overflows `usize`.
264 /// use std::collections::HashSet;
265 /// let mut set: HashSet<i32> = HashSet::new();
267 /// assert!(set.capacity() >= 10);
269 #[stable(feature = "rust1", since = "1.0.0")]
270 pub fn reserve(&mut self, additional: usize) {
271 self.map.reserve(additional)
274 /// Shrinks the capacity of the set as much as possible. It will drop
275 /// down as much as possible while maintaining the internal rules
276 /// and possibly leaving some space in accordance with the resize policy.
281 /// use std::collections::HashSet;
283 /// let mut set = HashSet::with_capacity(100);
286 /// assert!(set.capacity() >= 100);
287 /// set.shrink_to_fit();
288 /// assert!(set.capacity() >= 2);
290 #[stable(feature = "rust1", since = "1.0.0")]
291 pub fn shrink_to_fit(&mut self) {
292 self.map.shrink_to_fit()
295 /// An iterator visiting all elements in arbitrary order.
296 /// The iterator element type is `&'a T`.
301 /// use std::collections::HashSet;
302 /// let mut set = HashSet::new();
306 /// // Will print in an arbitrary order.
307 /// for x in set.iter() {
308 /// println!("{}", x);
311 #[stable(feature = "rust1", since = "1.0.0")]
312 pub fn iter(&self) -> Iter<T> {
313 Iter { iter: self.map.keys() }
316 /// Visits the values representing the difference,
317 /// i.e. the values that are in `self` but not in `other`.
322 /// use std::collections::HashSet;
323 /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
324 /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
326 /// // Can be seen as `a - b`.
327 /// for x in a.difference(&b) {
328 /// println!("{}", x); // Print 1
331 /// let diff: HashSet<_> = a.difference(&b).collect();
332 /// assert_eq!(diff, [1].iter().collect());
334 /// // Note that difference is not symmetric,
335 /// // and `b - a` means something else:
336 /// let diff: HashSet<_> = b.difference(&a).collect();
337 /// assert_eq!(diff, [4].iter().collect());
339 #[stable(feature = "rust1", since = "1.0.0")]
340 pub fn difference<'a>(&'a self, other: &'a HashSet<T, S>) -> Difference<'a, T, S> {
347 /// Visits the values representing the symmetric difference,
348 /// i.e. the values that are in `self` or in `other` but not in both.
353 /// use std::collections::HashSet;
354 /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
355 /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
357 /// // Print 1, 4 in arbitrary order.
358 /// for x in a.symmetric_difference(&b) {
359 /// println!("{}", x);
362 /// let diff1: HashSet<_> = a.symmetric_difference(&b).collect();
363 /// let diff2: HashSet<_> = b.symmetric_difference(&a).collect();
365 /// assert_eq!(diff1, diff2);
366 /// assert_eq!(diff1, [1, 4].iter().collect());
368 #[stable(feature = "rust1", since = "1.0.0")]
369 pub fn symmetric_difference<'a>(&'a self,
370 other: &'a HashSet<T, S>)
371 -> SymmetricDifference<'a, T, S> {
372 SymmetricDifference { iter: self.difference(other).chain(other.difference(self)) }
375 /// Visits the values representing the intersection,
376 /// i.e. the values that are both in `self` and `other`.
381 /// use std::collections::HashSet;
382 /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
383 /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
385 /// // Print 2, 3 in arbitrary order.
386 /// for x in a.intersection(&b) {
387 /// println!("{}", x);
390 /// let intersection: HashSet<_> = a.intersection(&b).collect();
391 /// assert_eq!(intersection, [2, 3].iter().collect());
393 #[stable(feature = "rust1", since = "1.0.0")]
394 pub fn intersection<'a>(&'a self, other: &'a HashSet<T, S>) -> Intersection<'a, T, S> {
401 /// Visits the values representing the union,
402 /// i.e. all the values in `self` or `other`, without duplicates.
407 /// use std::collections::HashSet;
408 /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
409 /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
411 /// // Print 1, 2, 3, 4 in arbitrary order.
412 /// for x in a.union(&b) {
413 /// println!("{}", x);
416 /// let union: HashSet<_> = a.union(&b).collect();
417 /// assert_eq!(union, [1, 2, 3, 4].iter().collect());
419 #[stable(feature = "rust1", since = "1.0.0")]
420 pub fn union<'a>(&'a self, other: &'a HashSet<T, S>) -> Union<'a, T, S> {
421 Union { iter: self.iter().chain(other.difference(self)) }
424 /// Returns the number of elements in the set.
429 /// use std::collections::HashSet;
431 /// let mut v = HashSet::new();
432 /// assert_eq!(v.len(), 0);
434 /// assert_eq!(v.len(), 1);
436 #[stable(feature = "rust1", since = "1.0.0")]
437 pub fn len(&self) -> usize {
441 /// Returns true if the set contains no elements.
446 /// use std::collections::HashSet;
448 /// let mut v = HashSet::new();
449 /// assert!(v.is_empty());
451 /// assert!(!v.is_empty());
453 #[stable(feature = "rust1", since = "1.0.0")]
454 pub fn is_empty(&self) -> bool {
458 /// Clears the set, returning all elements in an iterator.
463 /// use std::collections::HashSet;
465 /// let mut set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
466 /// assert!(!set.is_empty());
468 /// // print 1, 2, 3 in an arbitrary order
469 /// for i in set.drain() {
470 /// println!("{}", i);
473 /// assert!(set.is_empty());
476 #[stable(feature = "drain", since = "1.6.0")]
477 pub fn drain(&mut self) -> Drain<T> {
478 Drain { iter: self.map.drain() }
481 /// Clears the set, removing all values.
486 /// use std::collections::HashSet;
488 /// let mut v = HashSet::new();
491 /// assert!(v.is_empty());
493 #[stable(feature = "rust1", since = "1.0.0")]
494 pub fn clear(&mut self) {
498 /// Returns `true` if the set contains a value.
500 /// The value may be any borrowed form of the set's value type, but
501 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
507 /// use std::collections::HashSet;
509 /// let set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
510 /// assert_eq!(set.contains(&1), true);
511 /// assert_eq!(set.contains(&4), false);
514 /// [`Eq`]: ../../std/cmp/trait.Eq.html
515 /// [`Hash`]: ../../std/hash/trait.Hash.html
516 #[stable(feature = "rust1", since = "1.0.0")]
517 pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool
521 self.map.contains_key(value)
524 /// Returns a reference to the value in the set, if any, that is equal to the given value.
526 /// The value may be any borrowed form of the set's value type, but
527 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
533 /// use std::collections::HashSet;
535 /// let set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
536 /// assert_eq!(set.get(&2), Some(&2));
537 /// assert_eq!(set.get(&4), None);
540 /// [`Eq`]: ../../std/cmp/trait.Eq.html
541 /// [`Hash`]: ../../std/hash/trait.Hash.html
542 #[stable(feature = "set_recovery", since = "1.9.0")]
543 pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<&T>
547 Recover::get(&self.map, value)
550 /// Returns `true` if `self` has no elements in common with `other`.
551 /// This is equivalent to checking for an empty intersection.
556 /// use std::collections::HashSet;
558 /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
559 /// let mut b = HashSet::new();
561 /// assert_eq!(a.is_disjoint(&b), true);
563 /// assert_eq!(a.is_disjoint(&b), true);
565 /// assert_eq!(a.is_disjoint(&b), false);
567 #[stable(feature = "rust1", since = "1.0.0")]
568 pub fn is_disjoint(&self, other: &HashSet<T, S>) -> bool {
569 self.iter().all(|v| !other.contains(v))
572 /// Returns `true` if the set is a subset of another,
573 /// i.e. `other` contains at least all the values in `self`.
578 /// use std::collections::HashSet;
580 /// let sup: HashSet<_> = [1, 2, 3].iter().cloned().collect();
581 /// let mut set = HashSet::new();
583 /// assert_eq!(set.is_subset(&sup), true);
585 /// assert_eq!(set.is_subset(&sup), true);
587 /// assert_eq!(set.is_subset(&sup), false);
589 #[stable(feature = "rust1", since = "1.0.0")]
590 pub fn is_subset(&self, other: &HashSet<T, S>) -> bool {
591 self.iter().all(|v| other.contains(v))
594 /// Returns `true` if the set is a superset of another,
595 /// i.e. `self` contains at least all the values in `other`.
600 /// use std::collections::HashSet;
602 /// let sub: HashSet<_> = [1, 2].iter().cloned().collect();
603 /// let mut set = HashSet::new();
605 /// assert_eq!(set.is_superset(&sub), false);
609 /// assert_eq!(set.is_superset(&sub), false);
612 /// assert_eq!(set.is_superset(&sub), true);
615 #[stable(feature = "rust1", since = "1.0.0")]
616 pub fn is_superset(&self, other: &HashSet<T, S>) -> bool {
617 other.is_subset(self)
620 /// Adds a value to the set.
622 /// If the set did not have this value present, `true` is returned.
624 /// If the set did have this value present, `false` is returned.
629 /// use std::collections::HashSet;
631 /// let mut set = HashSet::new();
633 /// assert_eq!(set.insert(2), true);
634 /// assert_eq!(set.insert(2), false);
635 /// assert_eq!(set.len(), 1);
637 #[stable(feature = "rust1", since = "1.0.0")]
638 pub fn insert(&mut self, value: T) -> bool {
639 self.map.insert(value, ()).is_none()
642 /// Adds a value to the set, replacing the existing value, if any, that is equal to the given
643 /// one. Returns the replaced value.
648 /// use std::collections::HashSet;
650 /// let mut set = HashSet::new();
651 /// set.insert(Vec::<i32>::new());
653 /// assert_eq!(set.get(&[][..]).unwrap().capacity(), 0);
654 /// set.replace(Vec::with_capacity(10));
655 /// assert_eq!(set.get(&[][..]).unwrap().capacity(), 10);
657 #[stable(feature = "set_recovery", since = "1.9.0")]
658 pub fn replace(&mut self, value: T) -> Option<T> {
659 Recover::replace(&mut self.map, value)
662 /// Removes a value from the set. Returns `true` if the value was
663 /// present in the set.
665 /// The value may be any borrowed form of the set's value type, but
666 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
672 /// use std::collections::HashSet;
674 /// let mut set = HashSet::new();
677 /// assert_eq!(set.remove(&2), true);
678 /// assert_eq!(set.remove(&2), false);
681 /// [`Eq`]: ../../std/cmp/trait.Eq.html
682 /// [`Hash`]: ../../std/hash/trait.Hash.html
683 #[stable(feature = "rust1", since = "1.0.0")]
684 pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
688 self.map.remove(value).is_some()
691 /// Removes and returns the value in the set, if any, that is equal to the given one.
693 /// The value may be any borrowed form of the set's value type, but
694 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
700 /// use std::collections::HashSet;
702 /// let mut set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
703 /// assert_eq!(set.take(&2), Some(2));
704 /// assert_eq!(set.take(&2), None);
707 /// [`Eq`]: ../../std/cmp/trait.Eq.html
708 /// [`Hash`]: ../../std/hash/trait.Hash.html
709 #[stable(feature = "set_recovery", since = "1.9.0")]
710 pub fn take<Q: ?Sized>(&mut self, value: &Q) -> Option<T>
714 Recover::take(&mut self.map, value)
717 /// Retains only the elements specified by the predicate.
719 /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
724 /// use std::collections::HashSet;
726 /// let xs = [1,2,3,4,5,6];
727 /// let mut set: HashSet<i32> = xs.iter().cloned().collect();
728 /// set.retain(|&k| k % 2 == 0);
729 /// assert_eq!(set.len(), 3);
731 #[stable(feature = "retain_hash_collection", since = "1.18.0")]
732 pub fn retain<F>(&mut self, mut f: F)
733 where F: FnMut(&T) -> bool
735 self.map.retain(|k, _| f(k));
739 #[stable(feature = "rust1", since = "1.0.0")]
740 impl<T, S> PartialEq for HashSet<T, S>
744 fn eq(&self, other: &HashSet<T, S>) -> bool {
745 if self.len() != other.len() {
749 self.iter().all(|key| other.contains(key))
753 #[stable(feature = "rust1", since = "1.0.0")]
754 impl<T, S> Eq for HashSet<T, S>
760 #[stable(feature = "rust1", since = "1.0.0")]
761 impl<T, S> fmt::Debug for HashSet<T, S>
762 where T: Eq + Hash + fmt::Debug,
765 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
766 f.debug_set().entries(self.iter()).finish()
770 #[stable(feature = "rust1", since = "1.0.0")]
771 impl<T, S> FromIterator<T> for HashSet<T, S>
773 S: BuildHasher + Default
775 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> HashSet<T, S> {
776 let mut set = HashSet::with_hasher(Default::default());
782 #[stable(feature = "rust1", since = "1.0.0")]
783 impl<T, S> Extend<T> for HashSet<T, S>
787 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
788 self.map.extend(iter.into_iter().map(|k| (k, ())));
792 #[stable(feature = "hash_extend_copy", since = "1.4.0")]
793 impl<'a, T, S> Extend<&'a T> for HashSet<T, S>
794 where T: 'a + Eq + Hash + Copy,
797 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
798 self.extend(iter.into_iter().cloned());
802 #[stable(feature = "rust1", since = "1.0.0")]
803 impl<T, S> Default for HashSet<T, S>
805 S: BuildHasher + Default
807 /// Creates an empty `HashSet<T, S>` with the `Default` value for the hasher.
808 fn default() -> HashSet<T, S> {
809 HashSet { map: HashMap::default() }
813 #[stable(feature = "rust1", since = "1.0.0")]
814 impl<'a, 'b, T, S> BitOr<&'b HashSet<T, S>> for &'a HashSet<T, S>
815 where T: Eq + Hash + Clone,
816 S: BuildHasher + Default
818 type Output = HashSet<T, S>;
820 /// Returns the union of `self` and `rhs` as a new `HashSet<T, S>`.
825 /// use std::collections::HashSet;
827 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
828 /// let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();
830 /// let set = &a | &b;
833 /// let expected = [1, 2, 3, 4, 5];
835 /// assert!(expected.contains(x));
838 /// assert_eq!(i, expected.len());
840 fn bitor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
841 self.union(rhs).cloned().collect()
845 #[stable(feature = "rust1", since = "1.0.0")]
846 impl<'a, 'b, T, S> BitAnd<&'b HashSet<T, S>> for &'a HashSet<T, S>
847 where T: Eq + Hash + Clone,
848 S: BuildHasher + Default
850 type Output = HashSet<T, S>;
852 /// Returns the intersection of `self` and `rhs` as a new `HashSet<T, S>`.
857 /// use std::collections::HashSet;
859 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
860 /// let b: HashSet<_> = vec![2, 3, 4].into_iter().collect();
862 /// let set = &a & &b;
865 /// let expected = [2, 3];
867 /// assert!(expected.contains(x));
870 /// assert_eq!(i, expected.len());
872 fn bitand(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
873 self.intersection(rhs).cloned().collect()
877 #[stable(feature = "rust1", since = "1.0.0")]
878 impl<'a, 'b, T, S> BitXor<&'b HashSet<T, S>> for &'a HashSet<T, S>
879 where T: Eq + Hash + Clone,
880 S: BuildHasher + Default
882 type Output = HashSet<T, S>;
884 /// Returns the symmetric difference of `self` and `rhs` as a new `HashSet<T, S>`.
889 /// use std::collections::HashSet;
891 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
892 /// let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();
894 /// let set = &a ^ &b;
897 /// let expected = [1, 2, 4, 5];
899 /// assert!(expected.contains(x));
902 /// assert_eq!(i, expected.len());
904 fn bitxor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
905 self.symmetric_difference(rhs).cloned().collect()
909 #[stable(feature = "rust1", since = "1.0.0")]
910 impl<'a, 'b, T, S> Sub<&'b HashSet<T, S>> for &'a HashSet<T, S>
911 where T: Eq + Hash + Clone,
912 S: BuildHasher + Default
914 type Output = HashSet<T, S>;
916 /// Returns the difference of `self` and `rhs` as a new `HashSet<T, S>`.
921 /// use std::collections::HashSet;
923 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
924 /// let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();
926 /// let set = &a - &b;
929 /// let expected = [1, 2];
931 /// assert!(expected.contains(x));
934 /// assert_eq!(i, expected.len());
936 fn sub(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
937 self.difference(rhs).cloned().collect()
941 /// An iterator over the items of a `HashSet`.
943 /// This `struct` is created by the [`iter`] method on [`HashSet`].
944 /// See its documentation for more.
946 /// [`HashSet`]: struct.HashSet.html
947 /// [`iter`]: struct.HashSet.html#method.iter
948 #[stable(feature = "rust1", since = "1.0.0")]
949 pub struct Iter<'a, K: 'a> {
950 iter: Keys<'a, K, ()>,
953 /// An owning iterator over the items of a `HashSet`.
955 /// This `struct` is created by the [`into_iter`] method on [`HashSet`][`HashSet`]
956 /// (provided by the `IntoIterator` trait). See its documentation for more.
958 /// [`HashSet`]: struct.HashSet.html
959 /// [`into_iter`]: struct.HashSet.html#method.into_iter
960 #[stable(feature = "rust1", since = "1.0.0")]
961 pub struct IntoIter<K> {
962 iter: map::IntoIter<K, ()>,
965 /// A draining iterator over the items of a `HashSet`.
967 /// This `struct` is created by the [`drain`] method on [`HashSet`].
968 /// See its documentation for more.
970 /// [`HashSet`]: struct.HashSet.html
971 /// [`drain`]: struct.HashSet.html#method.drain
972 #[stable(feature = "rust1", since = "1.0.0")]
973 pub struct Drain<'a, K: 'a> {
974 iter: map::Drain<'a, K, ()>,
977 /// A lazy iterator producing elements in the intersection of `HashSet`s.
979 /// This `struct` is created by the [`intersection`] method on [`HashSet`].
980 /// See its documentation for more.
982 /// [`HashSet`]: struct.HashSet.html
983 /// [`intersection`]: struct.HashSet.html#method.intersection
984 #[stable(feature = "rust1", since = "1.0.0")]
985 pub struct Intersection<'a, T: 'a, S: 'a> {
986 // iterator of the first set
989 other: &'a HashSet<T, S>,
992 /// A lazy iterator producing elements in the difference of `HashSet`s.
994 /// This `struct` is created by the [`difference`] method on [`HashSet`].
995 /// See its documentation for more.
997 /// [`HashSet`]: struct.HashSet.html
998 /// [`difference`]: struct.HashSet.html#method.difference
999 #[stable(feature = "rust1", since = "1.0.0")]
1000 pub struct Difference<'a, T: 'a, S: 'a> {
1001 // iterator of the first set
1004 other: &'a HashSet<T, S>,
1007 /// A lazy iterator producing elements in the symmetric difference of `HashSet`s.
1009 /// This `struct` is created by the [`symmetric_difference`] method on
1010 /// [`HashSet`]. See its documentation for more.
1012 /// [`HashSet`]: struct.HashSet.html
1013 /// [`symmetric_difference`]: struct.HashSet.html#method.symmetric_difference
1014 #[stable(feature = "rust1", since = "1.0.0")]
1015 pub struct SymmetricDifference<'a, T: 'a, S: 'a> {
1016 iter: Chain<Difference<'a, T, S>, Difference<'a, T, S>>,
1019 /// A lazy iterator producing elements in the union of `HashSet`s.
1021 /// This `struct` is created by the [`union`] method on [`HashSet`].
1022 /// See its documentation for more.
1024 /// [`HashSet`]: struct.HashSet.html
1025 /// [`union`]: struct.HashSet.html#method.union
1026 #[stable(feature = "rust1", since = "1.0.0")]
1027 pub struct Union<'a, T: 'a, S: 'a> {
1028 iter: Chain<Iter<'a, T>, Difference<'a, T, S>>,
1031 #[stable(feature = "rust1", since = "1.0.0")]
1032 impl<'a, T, S> IntoIterator for &'a HashSet<T, S>
1037 type IntoIter = Iter<'a, T>;
1039 fn into_iter(self) -> Iter<'a, T> {
1044 #[stable(feature = "rust1", since = "1.0.0")]
1045 impl<T, S> IntoIterator for HashSet<T, S>
1050 type IntoIter = IntoIter<T>;
1052 /// Creates a consuming iterator, that is, one that moves each value out
1053 /// of the set in arbitrary order. The set cannot be used after calling
1059 /// use std::collections::HashSet;
1060 /// let mut set = HashSet::new();
1061 /// set.insert("a".to_string());
1062 /// set.insert("b".to_string());
1064 /// // Not possible to collect to a Vec<String> with a regular `.iter()`.
1065 /// let v: Vec<String> = set.into_iter().collect();
1067 /// // Will print in an arbitrary order.
1069 /// println!("{}", x);
1072 fn into_iter(self) -> IntoIter<T> {
1073 IntoIter { iter: self.map.into_iter() }
1077 #[stable(feature = "rust1", since = "1.0.0")]
1078 impl<'a, K> Clone for Iter<'a, K> {
1079 fn clone(&self) -> Iter<'a, K> {
1080 Iter { iter: self.iter.clone() }
1083 #[stable(feature = "rust1", since = "1.0.0")]
1084 impl<'a, K> Iterator for Iter<'a, K> {
1087 fn next(&mut self) -> Option<&'a K> {
1090 fn size_hint(&self) -> (usize, Option<usize>) {
1091 self.iter.size_hint()
1094 #[stable(feature = "rust1", since = "1.0.0")]
1095 impl<'a, K> ExactSizeIterator for Iter<'a, K> {
1096 fn len(&self) -> usize {
1100 #[stable(feature = "fused", since = "1.26.0")]
1101 impl<'a, K> FusedIterator for Iter<'a, K> {}
1103 #[stable(feature = "std_debug", since = "1.16.0")]
1104 impl<'a, K: fmt::Debug> fmt::Debug for Iter<'a, K> {
1105 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1106 f.debug_list().entries(self.clone()).finish()
1110 #[stable(feature = "rust1", since = "1.0.0")]
1111 impl<K> Iterator for IntoIter<K> {
1114 fn next(&mut self) -> Option<K> {
1115 self.iter.next().map(|(k, _)| k)
1117 fn size_hint(&self) -> (usize, Option<usize>) {
1118 self.iter.size_hint()
1121 #[stable(feature = "rust1", since = "1.0.0")]
1122 impl<K> ExactSizeIterator for IntoIter<K> {
1123 fn len(&self) -> usize {
1127 #[stable(feature = "fused", since = "1.26.0")]
1128 impl<K> FusedIterator for IntoIter<K> {}
1130 #[stable(feature = "std_debug", since = "1.16.0")]
1131 impl<K: fmt::Debug> fmt::Debug for IntoIter<K> {
1132 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1133 let entries_iter = self.iter
1137 f.debug_list().entries(entries_iter).finish()
1141 #[stable(feature = "rust1", since = "1.0.0")]
1142 impl<'a, K> Iterator for Drain<'a, K> {
1145 fn next(&mut self) -> Option<K> {
1146 self.iter.next().map(|(k, _)| k)
1148 fn size_hint(&self) -> (usize, Option<usize>) {
1149 self.iter.size_hint()
1152 #[stable(feature = "rust1", since = "1.0.0")]
1153 impl<'a, K> ExactSizeIterator for Drain<'a, K> {
1154 fn len(&self) -> usize {
1158 #[stable(feature = "fused", since = "1.26.0")]
1159 impl<'a, K> FusedIterator for Drain<'a, K> {}
1161 #[stable(feature = "std_debug", since = "1.16.0")]
1162 impl<'a, K: fmt::Debug> fmt::Debug for Drain<'a, K> {
1163 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1164 let entries_iter = self.iter
1168 f.debug_list().entries(entries_iter).finish()
1172 #[stable(feature = "rust1", since = "1.0.0")]
1173 impl<'a, T, S> Clone for Intersection<'a, T, S> {
1174 fn clone(&self) -> Intersection<'a, T, S> {
1175 Intersection { iter: self.iter.clone(), ..*self }
1179 #[stable(feature = "rust1", since = "1.0.0")]
1180 impl<'a, T, S> Iterator for Intersection<'a, T, S>
1186 fn next(&mut self) -> Option<&'a T> {
1188 let elt = self.iter.next()?;
1189 if self.other.contains(elt) {
1195 fn size_hint(&self) -> (usize, Option<usize>) {
1196 let (_, upper) = self.iter.size_hint();
1201 #[stable(feature = "std_debug", since = "1.16.0")]
1202 impl<'a, T, S> fmt::Debug for Intersection<'a, T, S>
1203 where T: fmt::Debug + Eq + Hash,
1206 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1207 f.debug_list().entries(self.clone()).finish()
1211 #[stable(feature = "fused", since = "1.26.0")]
1212 impl<'a, T, S> FusedIterator for Intersection<'a, T, S>
1218 #[stable(feature = "rust1", since = "1.0.0")]
1219 impl<'a, T, S> Clone for Difference<'a, T, S> {
1220 fn clone(&self) -> Difference<'a, T, S> {
1221 Difference { iter: self.iter.clone(), ..*self }
1225 #[stable(feature = "rust1", since = "1.0.0")]
1226 impl<'a, T, S> Iterator for Difference<'a, T, S>
1232 fn next(&mut self) -> Option<&'a T> {
1234 let elt = self.iter.next()?;
1235 if !self.other.contains(elt) {
1241 fn size_hint(&self) -> (usize, Option<usize>) {
1242 let (_, upper) = self.iter.size_hint();
1247 #[stable(feature = "fused", since = "1.26.0")]
1248 impl<'a, T, S> FusedIterator for Difference<'a, T, S>
1254 #[stable(feature = "std_debug", since = "1.16.0")]
1255 impl<'a, T, S> fmt::Debug for Difference<'a, T, S>
1256 where T: fmt::Debug + Eq + Hash,
1259 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1260 f.debug_list().entries(self.clone()).finish()
1264 #[stable(feature = "rust1", since = "1.0.0")]
1265 impl<'a, T, S> Clone for SymmetricDifference<'a, T, S> {
1266 fn clone(&self) -> SymmetricDifference<'a, T, S> {
1267 SymmetricDifference { iter: self.iter.clone() }
1271 #[stable(feature = "rust1", since = "1.0.0")]
1272 impl<'a, T, S> Iterator for SymmetricDifference<'a, T, S>
1278 fn next(&mut self) -> Option<&'a T> {
1281 fn size_hint(&self) -> (usize, Option<usize>) {
1282 self.iter.size_hint()
1286 #[stable(feature = "fused", since = "1.26.0")]
1287 impl<'a, T, S> FusedIterator for SymmetricDifference<'a, T, S>
1293 #[stable(feature = "std_debug", since = "1.16.0")]
1294 impl<'a, T, S> fmt::Debug for SymmetricDifference<'a, T, S>
1295 where T: fmt::Debug + Eq + Hash,
1298 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1299 f.debug_list().entries(self.clone()).finish()
1303 #[stable(feature = "rust1", since = "1.0.0")]
1304 impl<'a, T, S> Clone for Union<'a, T, S> {
1305 fn clone(&self) -> Union<'a, T, S> {
1306 Union { iter: self.iter.clone() }
1310 #[stable(feature = "fused", since = "1.26.0")]
1311 impl<'a, T, S> FusedIterator for Union<'a, T, S>
1317 #[stable(feature = "std_debug", since = "1.16.0")]
1318 impl<'a, T, S> fmt::Debug for Union<'a, T, S>
1319 where T: fmt::Debug + Eq + Hash,
1322 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1323 f.debug_list().entries(self.clone()).finish()
1327 #[stable(feature = "rust1", since = "1.0.0")]
1328 impl<'a, T, S> Iterator for Union<'a, T, S>
1334 fn next(&mut self) -> Option<&'a T> {
1337 fn size_hint(&self) -> (usize, Option<usize>) {
1338 self.iter.size_hint()
1343 fn assert_covariance() {
1344 fn set<'new>(v: HashSet<&'static str>) -> HashSet<&'new str> {
1347 fn iter<'a, 'new>(v: Iter<'a, &'static str>) -> Iter<'a, &'new str> {
1350 fn into_iter<'new>(v: IntoIter<&'static str>) -> IntoIter<&'new str> {
1353 fn difference<'a, 'new>(v: Difference<'a, &'static str, RandomState>)
1354 -> Difference<'a, &'new str, RandomState> {
1357 fn symmetric_difference<'a, 'new>(v: SymmetricDifference<'a, &'static str, RandomState>)
1358 -> SymmetricDifference<'a, &'new str, RandomState> {
1361 fn intersection<'a, 'new>(v: Intersection<'a, &'static str, RandomState>)
1362 -> Intersection<'a, &'new str, RandomState> {
1365 fn union<'a, 'new>(v: Union<'a, &'static str, RandomState>)
1366 -> Union<'a, &'new str, RandomState> {
1369 fn drain<'new>(d: Drain<'static, &'static str>) -> Drain<'new, &'new str> {
1377 use super::super::map::RandomState;
1380 fn test_zero_capacities() {
1381 type HS = HashSet<i32>;
1384 assert_eq!(s.capacity(), 0);
1386 let s = HS::default();
1387 assert_eq!(s.capacity(), 0);
1389 let s = HS::with_hasher(RandomState::new());
1390 assert_eq!(s.capacity(), 0);
1392 let s = HS::with_capacity(0);
1393 assert_eq!(s.capacity(), 0);
1395 let s = HS::with_capacity_and_hasher(0, RandomState::new());
1396 assert_eq!(s.capacity(), 0);
1398 let mut s = HS::new();
1404 assert_eq!(s.capacity(), 0);
1406 let mut s = HS::new();
1408 assert_eq!(s.capacity(), 0);
1412 fn test_disjoint() {
1413 let mut xs = HashSet::new();
1414 let mut ys = HashSet::new();
1415 assert!(xs.is_disjoint(&ys));
1416 assert!(ys.is_disjoint(&xs));
1417 assert!(xs.insert(5));
1418 assert!(ys.insert(11));
1419 assert!(xs.is_disjoint(&ys));
1420 assert!(ys.is_disjoint(&xs));
1421 assert!(xs.insert(7));
1422 assert!(xs.insert(19));
1423 assert!(xs.insert(4));
1424 assert!(ys.insert(2));
1425 assert!(ys.insert(-11));
1426 assert!(xs.is_disjoint(&ys));
1427 assert!(ys.is_disjoint(&xs));
1428 assert!(ys.insert(7));
1429 assert!(!xs.is_disjoint(&ys));
1430 assert!(!ys.is_disjoint(&xs));
1434 fn test_subset_and_superset() {
1435 let mut a = HashSet::new();
1436 assert!(a.insert(0));
1437 assert!(a.insert(5));
1438 assert!(a.insert(11));
1439 assert!(a.insert(7));
1441 let mut b = HashSet::new();
1442 assert!(b.insert(0));
1443 assert!(b.insert(7));
1444 assert!(b.insert(19));
1445 assert!(b.insert(250));
1446 assert!(b.insert(11));
1447 assert!(b.insert(200));
1449 assert!(!a.is_subset(&b));
1450 assert!(!a.is_superset(&b));
1451 assert!(!b.is_subset(&a));
1452 assert!(!b.is_superset(&a));
1454 assert!(b.insert(5));
1456 assert!(a.is_subset(&b));
1457 assert!(!a.is_superset(&b));
1458 assert!(!b.is_subset(&a));
1459 assert!(b.is_superset(&a));
1464 let mut a = HashSet::new();
1466 assert!(a.insert(i));
1468 let mut observed: u32 = 0;
1470 observed |= 1 << *k;
1472 assert_eq!(observed, 0xFFFF_FFFF);
1476 fn test_intersection() {
1477 let mut a = HashSet::new();
1478 let mut b = HashSet::new();
1480 assert!(a.insert(11));
1481 assert!(a.insert(1));
1482 assert!(a.insert(3));
1483 assert!(a.insert(77));
1484 assert!(a.insert(103));
1485 assert!(a.insert(5));
1486 assert!(a.insert(-5));
1488 assert!(b.insert(2));
1489 assert!(b.insert(11));
1490 assert!(b.insert(77));
1491 assert!(b.insert(-9));
1492 assert!(b.insert(-42));
1493 assert!(b.insert(5));
1494 assert!(b.insert(3));
1497 let expected = [3, 5, 11, 77];
1498 for x in a.intersection(&b) {
1499 assert!(expected.contains(x));
1502 assert_eq!(i, expected.len());
1506 fn test_difference() {
1507 let mut a = HashSet::new();
1508 let mut b = HashSet::new();
1510 assert!(a.insert(1));
1511 assert!(a.insert(3));
1512 assert!(a.insert(5));
1513 assert!(a.insert(9));
1514 assert!(a.insert(11));
1516 assert!(b.insert(3));
1517 assert!(b.insert(9));
1520 let expected = [1, 5, 11];
1521 for x in a.difference(&b) {
1522 assert!(expected.contains(x));
1525 assert_eq!(i, expected.len());
1529 fn test_symmetric_difference() {
1530 let mut a = HashSet::new();
1531 let mut b = HashSet::new();
1533 assert!(a.insert(1));
1534 assert!(a.insert(3));
1535 assert!(a.insert(5));
1536 assert!(a.insert(9));
1537 assert!(a.insert(11));
1539 assert!(b.insert(-2));
1540 assert!(b.insert(3));
1541 assert!(b.insert(9));
1542 assert!(b.insert(14));
1543 assert!(b.insert(22));
1546 let expected = [-2, 1, 5, 11, 14, 22];
1547 for x in a.symmetric_difference(&b) {
1548 assert!(expected.contains(x));
1551 assert_eq!(i, expected.len());
1556 let mut a = HashSet::new();
1557 let mut b = HashSet::new();
1559 assert!(a.insert(1));
1560 assert!(a.insert(3));
1561 assert!(a.insert(5));
1562 assert!(a.insert(9));
1563 assert!(a.insert(11));
1564 assert!(a.insert(16));
1565 assert!(a.insert(19));
1566 assert!(a.insert(24));
1568 assert!(b.insert(-2));
1569 assert!(b.insert(1));
1570 assert!(b.insert(5));
1571 assert!(b.insert(9));
1572 assert!(b.insert(13));
1573 assert!(b.insert(19));
1576 let expected = [-2, 1, 3, 5, 9, 11, 13, 16, 19, 24];
1577 for x in a.union(&b) {
1578 assert!(expected.contains(x));
1581 assert_eq!(i, expected.len());
1585 fn test_from_iter() {
1586 let xs = [1, 2, 3, 4, 5, 6, 7, 8, 9];
1588 let set: HashSet<_> = xs.iter().cloned().collect();
1591 assert!(set.contains(x));
1596 fn test_move_iter() {
1598 let mut hs = HashSet::new();
1606 let v = hs.into_iter().collect::<Vec<char>>();
1607 assert!(v == ['a', 'b'] || v == ['b', 'a']);
1612 // These constants once happened to expose a bug in insert().
1613 // I'm keeping them around to prevent a regression.
1614 let mut s1 = HashSet::new();
1620 let mut s2 = HashSet::new();
1634 let mut set = HashSet::new();
1635 let empty = HashSet::<i32>::new();
1640 let set_str = format!("{:?}", set);
1642 assert!(set_str == "{1, 2}" || set_str == "{2, 1}");
1643 assert_eq!(format!("{:?}", empty), "{}");
1647 fn test_trivial_drain() {
1648 let mut s = HashSet::<i32>::new();
1649 for _ in s.drain() {}
1650 assert!(s.is_empty());
1653 let mut s = HashSet::<i32>::new();
1655 assert!(s.is_empty());
1660 let mut s: HashSet<_> = (1..100).collect();
1662 // try this a bunch of times to make sure we don't screw up internal state.
1664 assert_eq!(s.len(), 99);
1668 let mut d = s.drain();
1669 for (i, x) in d.by_ref().take(50).enumerate() {
1673 assert_eq!(last_i, 49);
1677 panic!("s should be empty!");
1680 // reset to try again.
1690 struct Foo(&'static str, i32);
1692 impl PartialEq for Foo {
1693 fn eq(&self, other: &Self) -> bool {
1700 impl hash::Hash for Foo {
1701 fn hash<H: hash::Hasher>(&self, h: &mut H) {
1706 let mut s = HashSet::new();
1707 assert_eq!(s.replace(Foo("a", 1)), None);
1708 assert_eq!(s.len(), 1);
1709 assert_eq!(s.replace(Foo("a", 2)), Some(Foo("a", 1)));
1710 assert_eq!(s.len(), 1);
1712 let mut it = s.iter();
1713 assert_eq!(it.next(), Some(&Foo("a", 2)));
1714 assert_eq!(it.next(), None);
1718 fn test_extend_ref() {
1719 let mut a = HashSet::new();
1722 a.extend(&[2, 3, 4]);
1724 assert_eq!(a.len(), 4);
1725 assert!(a.contains(&1));
1726 assert!(a.contains(&2));
1727 assert!(a.contains(&3));
1728 assert!(a.contains(&4));
1730 let mut b = HashSet::new();
1736 assert_eq!(a.len(), 6);
1737 assert!(a.contains(&1));
1738 assert!(a.contains(&2));
1739 assert!(a.contains(&3));
1740 assert!(a.contains(&4));
1741 assert!(a.contains(&5));
1742 assert!(a.contains(&6));
1747 let xs = [1, 2, 3, 4, 5, 6];
1748 let mut set: HashSet<i32> = xs.iter().cloned().collect();
1749 set.retain(|&k| k % 2 == 0);
1750 assert_eq!(set.len(), 3);
1751 assert!(set.contains(&2));
1752 assert!(set.contains(&4));
1753 assert!(set.contains(&6));