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
530 /// [`Eq`]: ../../std/cmp/trait.Eq.html
531 /// [`Hash`]: ../../std/hash/trait.Hash.html
532 #[stable(feature = "set_recovery", since = "1.9.0")]
533 pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<&T>
537 Recover::get(&self.map, value)
540 /// Returns `true` if `self` has no elements in common with `other`.
541 /// This is equivalent to checking for an empty intersection.
546 /// use std::collections::HashSet;
548 /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
549 /// let mut b = HashSet::new();
551 /// assert_eq!(a.is_disjoint(&b), true);
553 /// assert_eq!(a.is_disjoint(&b), true);
555 /// assert_eq!(a.is_disjoint(&b), false);
557 #[stable(feature = "rust1", since = "1.0.0")]
558 pub fn is_disjoint(&self, other: &HashSet<T, S>) -> bool {
559 self.iter().all(|v| !other.contains(v))
562 /// Returns `true` if the set is a subset of another,
563 /// i.e. `other` contains at least all the values in `self`.
568 /// use std::collections::HashSet;
570 /// let sup: HashSet<_> = [1, 2, 3].iter().cloned().collect();
571 /// let mut set = HashSet::new();
573 /// assert_eq!(set.is_subset(&sup), true);
575 /// assert_eq!(set.is_subset(&sup), true);
577 /// assert_eq!(set.is_subset(&sup), false);
579 #[stable(feature = "rust1", since = "1.0.0")]
580 pub fn is_subset(&self, other: &HashSet<T, S>) -> bool {
581 self.iter().all(|v| other.contains(v))
584 /// Returns `true` if the set is a superset of another,
585 /// i.e. `self` contains at least all the values in `other`.
590 /// use std::collections::HashSet;
592 /// let sub: HashSet<_> = [1, 2].iter().cloned().collect();
593 /// let mut set = HashSet::new();
595 /// assert_eq!(set.is_superset(&sub), false);
599 /// assert_eq!(set.is_superset(&sub), false);
602 /// assert_eq!(set.is_superset(&sub), true);
605 #[stable(feature = "rust1", since = "1.0.0")]
606 pub fn is_superset(&self, other: &HashSet<T, S>) -> bool {
607 other.is_subset(self)
610 /// Adds a value to the set.
612 /// If the set did not have this value present, `true` is returned.
614 /// If the set did have this value present, `false` is returned.
619 /// use std::collections::HashSet;
621 /// let mut set = HashSet::new();
623 /// assert_eq!(set.insert(2), true);
624 /// assert_eq!(set.insert(2), false);
625 /// assert_eq!(set.len(), 1);
627 #[stable(feature = "rust1", since = "1.0.0")]
628 pub fn insert(&mut self, value: T) -> bool {
629 self.map.insert(value, ()).is_none()
632 /// Adds a value to the set, replacing the existing value, if any, that is equal to the given
633 /// one. Returns the replaced value.
634 #[stable(feature = "set_recovery", since = "1.9.0")]
635 pub fn replace(&mut self, value: T) -> Option<T> {
636 Recover::replace(&mut self.map, value)
639 /// Removes a value from the set. Returns `true` if the value was
640 /// present in the set.
642 /// The value may be any borrowed form of the set's value type, but
643 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
649 /// use std::collections::HashSet;
651 /// let mut set = HashSet::new();
654 /// assert_eq!(set.remove(&2), true);
655 /// assert_eq!(set.remove(&2), false);
658 /// [`Eq`]: ../../std/cmp/trait.Eq.html
659 /// [`Hash`]: ../../std/hash/trait.Hash.html
660 #[stable(feature = "rust1", since = "1.0.0")]
661 pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
665 self.map.remove(value).is_some()
668 /// Removes and returns the value in the set, if any, that is equal to the given one.
670 /// The value may be any borrowed form of the set's value type, but
671 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
674 /// [`Eq`]: ../../std/cmp/trait.Eq.html
675 /// [`Hash`]: ../../std/hash/trait.Hash.html
676 #[stable(feature = "set_recovery", since = "1.9.0")]
677 pub fn take<Q: ?Sized>(&mut self, value: &Q) -> Option<T>
681 Recover::take(&mut self.map, value)
684 /// Retains only the elements specified by the predicate.
686 /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
691 /// use std::collections::HashSet;
693 /// let xs = [1,2,3,4,5,6];
694 /// let mut set: HashSet<isize> = xs.iter().cloned().collect();
695 /// set.retain(|&k| k % 2 == 0);
696 /// assert_eq!(set.len(), 3);
698 #[stable(feature = "retain_hash_collection", since = "1.18.0")]
699 pub fn retain<F>(&mut self, mut f: F)
700 where F: FnMut(&T) -> bool
702 self.map.retain(|k, _| f(k));
706 #[stable(feature = "rust1", since = "1.0.0")]
707 impl<T, S> PartialEq for HashSet<T, S>
711 fn eq(&self, other: &HashSet<T, S>) -> bool {
712 if self.len() != other.len() {
716 self.iter().all(|key| other.contains(key))
720 #[stable(feature = "rust1", since = "1.0.0")]
721 impl<T, S> Eq for HashSet<T, S>
727 #[stable(feature = "rust1", since = "1.0.0")]
728 impl<T, S> fmt::Debug for HashSet<T, S>
729 where T: Eq + Hash + fmt::Debug,
732 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
733 f.debug_set().entries(self.iter()).finish()
737 #[stable(feature = "rust1", since = "1.0.0")]
738 impl<T, S> FromIterator<T> for HashSet<T, S>
740 S: BuildHasher + Default
742 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> HashSet<T, S> {
743 let mut set = HashSet::with_hasher(Default::default());
749 #[stable(feature = "rust1", since = "1.0.0")]
750 impl<T, S> Extend<T> for HashSet<T, S>
754 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
755 self.map.extend(iter.into_iter().map(|k| (k, ())));
759 #[stable(feature = "hash_extend_copy", since = "1.4.0")]
760 impl<'a, T, S> Extend<&'a T> for HashSet<T, S>
761 where T: 'a + Eq + Hash + Copy,
764 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
765 self.extend(iter.into_iter().cloned());
769 #[stable(feature = "rust1", since = "1.0.0")]
770 impl<T, S> Default for HashSet<T, S>
772 S: BuildHasher + Default
774 /// Creates an empty `HashSet<T, S>` with the `Default` value for the hasher.
775 fn default() -> HashSet<T, S> {
776 HashSet { map: HashMap::default() }
780 #[stable(feature = "rust1", since = "1.0.0")]
781 impl<'a, 'b, T, S> BitOr<&'b HashSet<T, S>> for &'a HashSet<T, S>
782 where T: Eq + Hash + Clone,
783 S: BuildHasher + Default
785 type Output = HashSet<T, S>;
787 /// Returns the union of `self` and `rhs` as a new `HashSet<T, S>`.
792 /// use std::collections::HashSet;
794 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
795 /// let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();
797 /// let set = &a | &b;
800 /// let expected = [1, 2, 3, 4, 5];
802 /// assert!(expected.contains(x));
805 /// assert_eq!(i, expected.len());
807 fn bitor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
808 self.union(rhs).cloned().collect()
812 #[stable(feature = "rust1", since = "1.0.0")]
813 impl<'a, 'b, T, S> BitAnd<&'b HashSet<T, S>> for &'a HashSet<T, S>
814 where T: Eq + Hash + Clone,
815 S: BuildHasher + Default
817 type Output = HashSet<T, S>;
819 /// Returns the intersection of `self` and `rhs` as a new `HashSet<T, S>`.
824 /// use std::collections::HashSet;
826 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
827 /// let b: HashSet<_> = vec![2, 3, 4].into_iter().collect();
829 /// let set = &a & &b;
832 /// let expected = [2, 3];
834 /// assert!(expected.contains(x));
837 /// assert_eq!(i, expected.len());
839 fn bitand(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
840 self.intersection(rhs).cloned().collect()
844 #[stable(feature = "rust1", since = "1.0.0")]
845 impl<'a, 'b, T, S> BitXor<&'b HashSet<T, S>> for &'a HashSet<T, S>
846 where T: Eq + Hash + Clone,
847 S: BuildHasher + Default
849 type Output = HashSet<T, S>;
851 /// Returns the symmetric difference of `self` and `rhs` as a new `HashSet<T, S>`.
856 /// use std::collections::HashSet;
858 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
859 /// let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();
861 /// let set = &a ^ &b;
864 /// let expected = [1, 2, 4, 5];
866 /// assert!(expected.contains(x));
869 /// assert_eq!(i, expected.len());
871 fn bitxor(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
872 self.symmetric_difference(rhs).cloned().collect()
876 #[stable(feature = "rust1", since = "1.0.0")]
877 impl<'a, 'b, T, S> Sub<&'b HashSet<T, S>> for &'a HashSet<T, S>
878 where T: Eq + Hash + Clone,
879 S: BuildHasher + Default
881 type Output = HashSet<T, S>;
883 /// Returns the difference of `self` and `rhs` as a new `HashSet<T, S>`.
888 /// use std::collections::HashSet;
890 /// let a: HashSet<_> = vec![1, 2, 3].into_iter().collect();
891 /// let b: HashSet<_> = vec![3, 4, 5].into_iter().collect();
893 /// let set = &a - &b;
896 /// let expected = [1, 2];
898 /// assert!(expected.contains(x));
901 /// assert_eq!(i, expected.len());
903 fn sub(self, rhs: &HashSet<T, S>) -> HashSet<T, S> {
904 self.difference(rhs).cloned().collect()
908 /// An iterator over the items of a `HashSet`.
910 /// This `struct` is created by the [`iter`] method on [`HashSet`].
911 /// See its documentation for more.
913 /// [`HashSet`]: struct.HashSet.html
914 /// [`iter`]: struct.HashSet.html#method.iter
915 #[stable(feature = "rust1", since = "1.0.0")]
916 pub struct Iter<'a, K: 'a> {
917 iter: Keys<'a, K, ()>,
920 /// An owning iterator over the items of a `HashSet`.
922 /// This `struct` is created by the [`into_iter`] method on [`HashSet`][`HashSet`]
923 /// (provided by the `IntoIterator` trait). See its documentation for more.
925 /// [`HashSet`]: struct.HashSet.html
926 /// [`into_iter`]: struct.HashSet.html#method.into_iter
927 #[stable(feature = "rust1", since = "1.0.0")]
928 pub struct IntoIter<K> {
929 iter: map::IntoIter<K, ()>,
932 /// A draining iterator over the items of a `HashSet`.
934 /// This `struct` is created by the [`drain`] method on [`HashSet`].
935 /// See its documentation for more.
937 /// [`HashSet`]: struct.HashSet.html
938 /// [`drain`]: struct.HashSet.html#method.drain
939 #[stable(feature = "rust1", since = "1.0.0")]
940 pub struct Drain<'a, K: 'a> {
941 iter: map::Drain<'a, K, ()>,
944 /// A lazy iterator producing elements in the intersection of `HashSet`s.
946 /// This `struct` is created by the [`intersection`] method on [`HashSet`].
947 /// See its documentation for more.
949 /// [`HashSet`]: struct.HashSet.html
950 /// [`intersection`]: struct.HashSet.html#method.intersection
951 #[stable(feature = "rust1", since = "1.0.0")]
952 pub struct Intersection<'a, T: 'a, S: 'a> {
953 // iterator of the first set
956 other: &'a HashSet<T, S>,
959 /// A lazy iterator producing elements in the difference of `HashSet`s.
961 /// This `struct` is created by the [`difference`] method on [`HashSet`].
962 /// See its documentation for more.
964 /// [`HashSet`]: struct.HashSet.html
965 /// [`difference`]: struct.HashSet.html#method.difference
966 #[stable(feature = "rust1", since = "1.0.0")]
967 pub struct Difference<'a, T: 'a, S: 'a> {
968 // iterator of the first set
971 other: &'a HashSet<T, S>,
974 /// A lazy iterator producing elements in the symmetric difference of `HashSet`s.
976 /// This `struct` is created by the [`symmetric_difference`] method on
977 /// [`HashSet`]. See its documentation for more.
979 /// [`HashSet`]: struct.HashSet.html
980 /// [`symmetric_difference`]: struct.HashSet.html#method.symmetric_difference
981 #[stable(feature = "rust1", since = "1.0.0")]
982 pub struct SymmetricDifference<'a, T: 'a, S: 'a> {
983 iter: Chain<Difference<'a, T, S>, Difference<'a, T, S>>,
986 /// A lazy iterator producing elements in the union of `HashSet`s.
988 /// This `struct` is created by the [`union`] method on [`HashSet`].
989 /// See its documentation for more.
991 /// [`HashSet`]: struct.HashSet.html
992 /// [`union`]: struct.HashSet.html#method.union
993 #[stable(feature = "rust1", since = "1.0.0")]
994 pub struct Union<'a, T: 'a, S: 'a> {
995 iter: Chain<Iter<'a, T>, Difference<'a, T, S>>,
998 #[stable(feature = "rust1", since = "1.0.0")]
999 impl<'a, T, S> IntoIterator for &'a HashSet<T, S>
1004 type IntoIter = Iter<'a, T>;
1006 fn into_iter(self) -> Iter<'a, T> {
1011 #[stable(feature = "rust1", since = "1.0.0")]
1012 impl<T, S> IntoIterator for HashSet<T, S>
1017 type IntoIter = IntoIter<T>;
1019 /// Creates a consuming iterator, that is, one that moves each value out
1020 /// of the set in arbitrary order. The set cannot be used after calling
1026 /// use std::collections::HashSet;
1027 /// let mut set = HashSet::new();
1028 /// set.insert("a".to_string());
1029 /// set.insert("b".to_string());
1031 /// // Not possible to collect to a Vec<String> with a regular `.iter()`.
1032 /// let v: Vec<String> = set.into_iter().collect();
1034 /// // Will print in an arbitrary order.
1036 /// println!("{}", x);
1039 fn into_iter(self) -> IntoIter<T> {
1040 IntoIter { iter: self.map.into_iter() }
1044 #[stable(feature = "rust1", since = "1.0.0")]
1045 impl<'a, K> Clone for Iter<'a, K> {
1046 fn clone(&self) -> Iter<'a, K> {
1047 Iter { iter: self.iter.clone() }
1050 #[stable(feature = "rust1", since = "1.0.0")]
1051 impl<'a, K> Iterator for Iter<'a, K> {
1054 fn next(&mut self) -> Option<&'a K> {
1057 fn size_hint(&self) -> (usize, Option<usize>) {
1058 self.iter.size_hint()
1061 #[stable(feature = "rust1", since = "1.0.0")]
1062 impl<'a, K> ExactSizeIterator for Iter<'a, K> {
1063 fn len(&self) -> usize {
1067 #[unstable(feature = "fused", issue = "35602")]
1068 impl<'a, K> FusedIterator for Iter<'a, K> {}
1070 #[stable(feature = "std_debug", since = "1.16.0")]
1071 impl<'a, K: fmt::Debug> fmt::Debug for Iter<'a, K> {
1072 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1073 f.debug_list().entries(self.clone()).finish()
1077 #[stable(feature = "rust1", since = "1.0.0")]
1078 impl<K> Iterator for IntoIter<K> {
1081 fn next(&mut self) -> Option<K> {
1082 self.iter.next().map(|(k, _)| k)
1084 fn size_hint(&self) -> (usize, Option<usize>) {
1085 self.iter.size_hint()
1088 #[stable(feature = "rust1", since = "1.0.0")]
1089 impl<K> ExactSizeIterator for IntoIter<K> {
1090 fn len(&self) -> usize {
1094 #[unstable(feature = "fused", issue = "35602")]
1095 impl<K> FusedIterator for IntoIter<K> {}
1097 #[stable(feature = "std_debug", since = "1.16.0")]
1098 impl<K: fmt::Debug> fmt::Debug for IntoIter<K> {
1099 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1100 let entries_iter = self.iter
1104 f.debug_list().entries(entries_iter).finish()
1108 #[stable(feature = "rust1", since = "1.0.0")]
1109 impl<'a, K> Iterator for Drain<'a, K> {
1112 fn next(&mut self) -> Option<K> {
1113 self.iter.next().map(|(k, _)| k)
1115 fn size_hint(&self) -> (usize, Option<usize>) {
1116 self.iter.size_hint()
1119 #[stable(feature = "rust1", since = "1.0.0")]
1120 impl<'a, K> ExactSizeIterator for Drain<'a, K> {
1121 fn len(&self) -> usize {
1125 #[unstable(feature = "fused", issue = "35602")]
1126 impl<'a, K> FusedIterator for Drain<'a, K> {}
1128 #[stable(feature = "std_debug", since = "1.16.0")]
1129 impl<'a, K: fmt::Debug> fmt::Debug for Drain<'a, K> {
1130 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1131 let entries_iter = self.iter
1135 f.debug_list().entries(entries_iter).finish()
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 impl<'a, T, S> Clone for Intersection<'a, T, S> {
1141 fn clone(&self) -> Intersection<'a, T, S> {
1142 Intersection { iter: self.iter.clone(), ..*self }
1146 #[stable(feature = "rust1", since = "1.0.0")]
1147 impl<'a, T, S> Iterator for Intersection<'a, T, S>
1153 fn next(&mut self) -> Option<&'a T> {
1155 match self.iter.next() {
1156 None => return None,
1158 if self.other.contains(elt) {
1166 fn size_hint(&self) -> (usize, Option<usize>) {
1167 let (_, upper) = self.iter.size_hint();
1172 #[stable(feature = "std_debug", since = "1.16.0")]
1173 impl<'a, T, S> fmt::Debug for Intersection<'a, T, S>
1174 where T: fmt::Debug + Eq + Hash,
1177 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1178 f.debug_list().entries(self.clone()).finish()
1182 #[unstable(feature = "fused", issue = "35602")]
1183 impl<'a, T, S> FusedIterator for Intersection<'a, T, S>
1189 #[stable(feature = "rust1", since = "1.0.0")]
1190 impl<'a, T, S> Clone for Difference<'a, T, S> {
1191 fn clone(&self) -> Difference<'a, T, S> {
1192 Difference { iter: self.iter.clone(), ..*self }
1196 #[stable(feature = "rust1", since = "1.0.0")]
1197 impl<'a, T, S> Iterator for Difference<'a, T, S>
1203 fn next(&mut self) -> Option<&'a T> {
1205 match self.iter.next() {
1206 None => return None,
1208 if !self.other.contains(elt) {
1216 fn size_hint(&self) -> (usize, Option<usize>) {
1217 let (_, upper) = self.iter.size_hint();
1222 #[unstable(feature = "fused", issue = "35602")]
1223 impl<'a, T, S> FusedIterator for Difference<'a, T, S>
1229 #[stable(feature = "std_debug", since = "1.16.0")]
1230 impl<'a, T, S> fmt::Debug for Difference<'a, T, S>
1231 where T: fmt::Debug + Eq + Hash,
1234 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1235 f.debug_list().entries(self.clone()).finish()
1239 #[stable(feature = "rust1", since = "1.0.0")]
1240 impl<'a, T, S> Clone for SymmetricDifference<'a, T, S> {
1241 fn clone(&self) -> SymmetricDifference<'a, T, S> {
1242 SymmetricDifference { iter: self.iter.clone() }
1246 #[stable(feature = "rust1", since = "1.0.0")]
1247 impl<'a, T, S> Iterator for SymmetricDifference<'a, T, S>
1253 fn next(&mut self) -> Option<&'a T> {
1256 fn size_hint(&self) -> (usize, Option<usize>) {
1257 self.iter.size_hint()
1261 #[unstable(feature = "fused", issue = "35602")]
1262 impl<'a, T, S> FusedIterator for SymmetricDifference<'a, T, S>
1268 #[stable(feature = "std_debug", since = "1.16.0")]
1269 impl<'a, T, S> fmt::Debug for SymmetricDifference<'a, T, S>
1270 where T: fmt::Debug + Eq + Hash,
1273 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1274 f.debug_list().entries(self.clone()).finish()
1278 #[stable(feature = "rust1", since = "1.0.0")]
1279 impl<'a, T, S> Clone for Union<'a, T, S> {
1280 fn clone(&self) -> Union<'a, T, S> {
1281 Union { iter: self.iter.clone() }
1285 #[unstable(feature = "fused", issue = "35602")]
1286 impl<'a, T, S> FusedIterator for Union<'a, T, S>
1292 #[stable(feature = "std_debug", since = "1.16.0")]
1293 impl<'a, T, S> fmt::Debug for Union<'a, T, S>
1294 where T: fmt::Debug + Eq + Hash,
1297 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1298 f.debug_list().entries(self.clone()).finish()
1302 #[stable(feature = "rust1", since = "1.0.0")]
1303 impl<'a, T, S> Iterator for Union<'a, T, S>
1309 fn next(&mut self) -> Option<&'a T> {
1312 fn size_hint(&self) -> (usize, Option<usize>) {
1313 self.iter.size_hint()
1318 fn assert_covariance() {
1319 fn set<'new>(v: HashSet<&'static str>) -> HashSet<&'new str> {
1322 fn iter<'a, 'new>(v: Iter<'a, &'static str>) -> Iter<'a, &'new str> {
1325 fn into_iter<'new>(v: IntoIter<&'static str>) -> IntoIter<&'new str> {
1328 fn difference<'a, 'new>(v: Difference<'a, &'static str, RandomState>)
1329 -> Difference<'a, &'new str, RandomState> {
1332 fn symmetric_difference<'a, 'new>(v: SymmetricDifference<'a, &'static str, RandomState>)
1333 -> SymmetricDifference<'a, &'new str, RandomState> {
1336 fn intersection<'a, 'new>(v: Intersection<'a, &'static str, RandomState>)
1337 -> Intersection<'a, &'new str, RandomState> {
1340 fn union<'a, 'new>(v: Union<'a, &'static str, RandomState>)
1341 -> Union<'a, &'new str, RandomState> {
1344 fn drain<'new>(d: Drain<'static, &'static str>) -> Drain<'new, &'new str> {
1352 use super::super::map::RandomState;
1355 fn test_zero_capacities() {
1356 type HS = HashSet<i32>;
1359 assert_eq!(s.capacity(), 0);
1361 let s = HS::default();
1362 assert_eq!(s.capacity(), 0);
1364 let s = HS::with_hasher(RandomState::new());
1365 assert_eq!(s.capacity(), 0);
1367 let s = HS::with_capacity(0);
1368 assert_eq!(s.capacity(), 0);
1370 let s = HS::with_capacity_and_hasher(0, RandomState::new());
1371 assert_eq!(s.capacity(), 0);
1373 let mut s = HS::new();
1379 assert_eq!(s.capacity(), 0);
1381 let mut s = HS::new();
1383 assert_eq!(s.capacity(), 0);
1387 fn test_disjoint() {
1388 let mut xs = HashSet::new();
1389 let mut ys = HashSet::new();
1390 assert!(xs.is_disjoint(&ys));
1391 assert!(ys.is_disjoint(&xs));
1392 assert!(xs.insert(5));
1393 assert!(ys.insert(11));
1394 assert!(xs.is_disjoint(&ys));
1395 assert!(ys.is_disjoint(&xs));
1396 assert!(xs.insert(7));
1397 assert!(xs.insert(19));
1398 assert!(xs.insert(4));
1399 assert!(ys.insert(2));
1400 assert!(ys.insert(-11));
1401 assert!(xs.is_disjoint(&ys));
1402 assert!(ys.is_disjoint(&xs));
1403 assert!(ys.insert(7));
1404 assert!(!xs.is_disjoint(&ys));
1405 assert!(!ys.is_disjoint(&xs));
1409 fn test_subset_and_superset() {
1410 let mut a = HashSet::new();
1411 assert!(a.insert(0));
1412 assert!(a.insert(5));
1413 assert!(a.insert(11));
1414 assert!(a.insert(7));
1416 let mut b = HashSet::new();
1417 assert!(b.insert(0));
1418 assert!(b.insert(7));
1419 assert!(b.insert(19));
1420 assert!(b.insert(250));
1421 assert!(b.insert(11));
1422 assert!(b.insert(200));
1424 assert!(!a.is_subset(&b));
1425 assert!(!a.is_superset(&b));
1426 assert!(!b.is_subset(&a));
1427 assert!(!b.is_superset(&a));
1429 assert!(b.insert(5));
1431 assert!(a.is_subset(&b));
1432 assert!(!a.is_superset(&b));
1433 assert!(!b.is_subset(&a));
1434 assert!(b.is_superset(&a));
1439 let mut a = HashSet::new();
1441 assert!(a.insert(i));
1443 let mut observed: u32 = 0;
1445 observed |= 1 << *k;
1447 assert_eq!(observed, 0xFFFF_FFFF);
1451 fn test_intersection() {
1452 let mut a = HashSet::new();
1453 let mut b = HashSet::new();
1455 assert!(a.insert(11));
1456 assert!(a.insert(1));
1457 assert!(a.insert(3));
1458 assert!(a.insert(77));
1459 assert!(a.insert(103));
1460 assert!(a.insert(5));
1461 assert!(a.insert(-5));
1463 assert!(b.insert(2));
1464 assert!(b.insert(11));
1465 assert!(b.insert(77));
1466 assert!(b.insert(-9));
1467 assert!(b.insert(-42));
1468 assert!(b.insert(5));
1469 assert!(b.insert(3));
1472 let expected = [3, 5, 11, 77];
1473 for x in a.intersection(&b) {
1474 assert!(expected.contains(x));
1477 assert_eq!(i, expected.len());
1481 fn test_difference() {
1482 let mut a = HashSet::new();
1483 let mut b = HashSet::new();
1485 assert!(a.insert(1));
1486 assert!(a.insert(3));
1487 assert!(a.insert(5));
1488 assert!(a.insert(9));
1489 assert!(a.insert(11));
1491 assert!(b.insert(3));
1492 assert!(b.insert(9));
1495 let expected = [1, 5, 11];
1496 for x in a.difference(&b) {
1497 assert!(expected.contains(x));
1500 assert_eq!(i, expected.len());
1504 fn test_symmetric_difference() {
1505 let mut a = HashSet::new();
1506 let mut b = HashSet::new();
1508 assert!(a.insert(1));
1509 assert!(a.insert(3));
1510 assert!(a.insert(5));
1511 assert!(a.insert(9));
1512 assert!(a.insert(11));
1514 assert!(b.insert(-2));
1515 assert!(b.insert(3));
1516 assert!(b.insert(9));
1517 assert!(b.insert(14));
1518 assert!(b.insert(22));
1521 let expected = [-2, 1, 5, 11, 14, 22];
1522 for x in a.symmetric_difference(&b) {
1523 assert!(expected.contains(x));
1526 assert_eq!(i, expected.len());
1531 let mut a = HashSet::new();
1532 let mut b = HashSet::new();
1534 assert!(a.insert(1));
1535 assert!(a.insert(3));
1536 assert!(a.insert(5));
1537 assert!(a.insert(9));
1538 assert!(a.insert(11));
1539 assert!(a.insert(16));
1540 assert!(a.insert(19));
1541 assert!(a.insert(24));
1543 assert!(b.insert(-2));
1544 assert!(b.insert(1));
1545 assert!(b.insert(5));
1546 assert!(b.insert(9));
1547 assert!(b.insert(13));
1548 assert!(b.insert(19));
1551 let expected = [-2, 1, 3, 5, 9, 11, 13, 16, 19, 24];
1552 for x in a.union(&b) {
1553 assert!(expected.contains(x));
1556 assert_eq!(i, expected.len());
1560 fn test_from_iter() {
1561 let xs = [1, 2, 3, 4, 5, 6, 7, 8, 9];
1563 let set: HashSet<_> = xs.iter().cloned().collect();
1566 assert!(set.contains(x));
1571 fn test_move_iter() {
1573 let mut hs = HashSet::new();
1581 let v = hs.into_iter().collect::<Vec<char>>();
1582 assert!(v == ['a', 'b'] || v == ['b', 'a']);
1587 // These constants once happened to expose a bug in insert().
1588 // I'm keeping them around to prevent a regression.
1589 let mut s1 = HashSet::new();
1595 let mut s2 = HashSet::new();
1609 let mut set = HashSet::new();
1610 let empty = HashSet::<i32>::new();
1615 let set_str = format!("{:?}", set);
1617 assert!(set_str == "{1, 2}" || set_str == "{2, 1}");
1618 assert_eq!(format!("{:?}", empty), "{}");
1622 fn test_trivial_drain() {
1623 let mut s = HashSet::<i32>::new();
1624 for _ in s.drain() {}
1625 assert!(s.is_empty());
1628 let mut s = HashSet::<i32>::new();
1630 assert!(s.is_empty());
1635 let mut s: HashSet<_> = (1..100).collect();
1637 // try this a bunch of times to make sure we don't screw up internal state.
1639 assert_eq!(s.len(), 99);
1643 let mut d = s.drain();
1644 for (i, x) in d.by_ref().take(50).enumerate() {
1648 assert_eq!(last_i, 49);
1652 panic!("s should be empty!");
1655 // reset to try again.
1665 struct Foo(&'static str, i32);
1667 impl PartialEq for Foo {
1668 fn eq(&self, other: &Self) -> bool {
1675 impl hash::Hash for Foo {
1676 fn hash<H: hash::Hasher>(&self, h: &mut H) {
1681 let mut s = HashSet::new();
1682 assert_eq!(s.replace(Foo("a", 1)), None);
1683 assert_eq!(s.len(), 1);
1684 assert_eq!(s.replace(Foo("a", 2)), Some(Foo("a", 1)));
1685 assert_eq!(s.len(), 1);
1687 let mut it = s.iter();
1688 assert_eq!(it.next(), Some(&Foo("a", 2)));
1689 assert_eq!(it.next(), None);
1693 fn test_extend_ref() {
1694 let mut a = HashSet::new();
1697 a.extend(&[2, 3, 4]);
1699 assert_eq!(a.len(), 4);
1700 assert!(a.contains(&1));
1701 assert!(a.contains(&2));
1702 assert!(a.contains(&3));
1703 assert!(a.contains(&4));
1705 let mut b = HashSet::new();
1711 assert_eq!(a.len(), 6);
1712 assert!(a.contains(&1));
1713 assert!(a.contains(&2));
1714 assert!(a.contains(&3));
1715 assert!(a.contains(&4));
1716 assert!(a.contains(&5));
1717 assert!(a.contains(&6));
1722 let xs = [1, 2, 3, 4, 5, 6];
1723 let mut set: HashSet<isize> = xs.iter().cloned().collect();
1724 set.retain(|&k| k % 2 == 0);
1725 assert_eq!(set.len(), 3);
1726 assert!(set.contains(&2));
1727 assert!(set.contains(&4));
1728 assert!(set.contains(&6));