1 // Copyright 2012-2014 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 /// An implementation of a set using a bit vector as an underlying
14 /// representation for holding unsigned numerical elements.
16 /// It should also be noted that the amount of storage necessary for holding a
17 /// set of objects is proportional to the maximum of the objects when viewed
23 /// # #![feature(collections)]
24 /// use std::collections::{BitSet, BitVec};
26 /// // It's a regular set
27 /// let mut s = BitSet::new();
34 /// if !s.contains(&7) {
35 /// println!("There is no 7");
38 /// // Can initialize from a `BitVec`
39 /// let other = BitSet::from_bit_vec(BitVec::from_bytes(&[0b11010000]));
41 /// s.union_with(&other);
43 /// // Print 0, 1, 3 in some order
44 /// for x in s.iter() {
45 /// println!("{}", x);
48 /// // Can convert back to a `BitVec`
49 /// let bv: BitVec = s.into_bit_vec();
57 use bit_vec::{BitVec, Blocks, BitBlock};
58 use std::cmp::Ordering;
62 use std::iter::{Chain, Enumerate, Repeat, Skip, Take, repeat};
63 use std::iter::{self, FromIterator};
65 type MatchWords<'a, B> = Chain<Enumerate<Blocks<'a, B>>, Skip<Take<Enumerate<Repeat<B>>>>>;
67 /// Computes how many blocks are needed to store that many bits
68 fn blocks_for_bits<B: BitBlock>(bits: usize) -> usize {
69 // If we want 17 bits, dividing by 32 will produce 0. So we add 1 to make sure we
70 // reserve enough. But if we want exactly a multiple of 32, this will actually allocate
71 // one too many. So we need to check if that's the case. We can do that by computing if
72 // bitwise AND by `32 - 1` is 0. But LLVM should be able to optimize the semantically
73 // superior modulo operator on a power of two to this.
75 // Note that we can technically avoid this branch with the expression
76 // `(nbits + u32::BITS - 1) / 32::BITS`, but if nbits is almost usize::MAX this will overflow.
77 if bits % B::bits() == 0 {
84 // Take two BitVec's, and return iterators of their words, where the shorter one
85 // has been padded with 0's
86 fn match_words<'a,'b, B: BitBlock>(a: &'a BitVec<B>, b: &'b BitVec<B>)
87 -> (MatchWords<'a, B>, MatchWords<'b, B>) {
88 let a_len = a.storage().len();
89 let b_len = b.storage().len();
91 // have to uselessly pretend to pad the longer one for type matching
93 (a.blocks().enumerate().chain(iter::repeat(B::zero()).enumerate().take(b_len).skip(a_len)),
94 b.blocks().enumerate().chain(iter::repeat(B::zero()).enumerate().take(0).skip(0)))
96 (a.blocks().enumerate().chain(iter::repeat(B::zero()).enumerate().take(0).skip(0)),
97 b.blocks().enumerate().chain(iter::repeat(B::zero()).enumerate().take(a_len).skip(b_len)))
101 pub struct BitSet<B=u32> {
105 impl<B: BitBlock> Clone for BitSet<B> {
106 fn clone(&self) -> Self {
108 bit_vec: self.bit_vec.clone(),
113 impl<B: BitBlock> Default for BitSet<B> {
115 fn default() -> Self { BitSet::new() }
118 impl<B: BitBlock> FromIterator<usize> for BitSet<B> {
119 fn from_iter<I: IntoIterator<Item=usize>>(iter: I) -> Self {
120 let mut ret = BitSet::new();
126 impl<B: BitBlock> Extend<usize> for BitSet<B> {
128 fn extend<I: IntoIterator<Item=usize>>(&mut self, iter: I) {
135 impl<B: BitBlock> PartialOrd for BitSet<B> {
137 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
138 let (a_iter, b_iter) = match_words(self.get_ref(), other.get_ref());
139 iter::order::partial_cmp(a_iter, b_iter)
143 impl<B: BitBlock> Ord for BitSet<B> {
145 fn cmp(&self, other: &Self) -> Ordering {
146 let (a_iter, b_iter) = match_words(self.get_ref(), other.get_ref());
147 iter::order::cmp(a_iter, b_iter)
151 impl<B: BitBlock> cmp::PartialEq for BitSet<B> {
153 fn eq(&self, other: &Self) -> bool {
154 let (a_iter, b_iter) = match_words(self.get_ref(), other.get_ref());
155 iter::order::eq(a_iter, b_iter)
159 impl<B: BitBlock> cmp::Eq for BitSet<B> {}
161 impl<B: BitBlock> BitSet<B> {
162 /// Creates a new empty `BitSet`.
167 /// # #![feature(collections)]
168 /// use std::collections::BitSet;
170 /// let mut s = BitSet::new();
173 pub fn new() -> Self {
174 BitSet { bit_vec: BitVec::new() }
177 /// Creates a new `BitSet` with initially no contents, able to
178 /// hold `nbits` elements without resizing.
183 /// # #![feature(collections)]
184 /// use std::collections::BitSet;
186 /// let mut s = BitSet::with_capacity(100);
187 /// assert!(s.capacity() >= 100);
190 pub fn with_capacity(nbits: usize) -> Self {
191 let bit_vec = BitVec::from_elem(nbits, false);
192 BitSet::from_bit_vec(bit_vec)
195 /// Creates a new `BitSet` from the given bit vector.
200 /// # #![feature(collections)]
201 /// use std::collections::{BitVec, BitSet};
203 /// let bv = BitVec::from_bytes(&[0b01100000]);
204 /// let s = BitSet::from_bit_vec(bv);
206 /// // Print 1, 2 in arbitrary order
207 /// for x in s.iter() {
208 /// println!("{}", x);
212 pub fn from_bit_vec(bit_vec: BitVec<B>) -> Self {
213 BitSet { bit_vec: bit_vec }
216 /// Returns the capacity in bits for this bit vector. Inserting any
217 /// element less than this amount will not trigger a resizing.
222 /// # #![feature(collections)]
223 /// use std::collections::BitSet;
225 /// let mut s = BitSet::with_capacity(100);
226 /// assert!(s.capacity() >= 100);
229 pub fn capacity(&self) -> usize {
230 self.bit_vec.capacity()
233 /// Reserves capacity for the given `BitSet` to contain `len` distinct elements. In the case
234 /// of `BitSet` this means reallocations will not occur as long as all inserted elements
235 /// are less than `len`.
237 /// The collection may reserve more space to avoid frequent reallocations.
243 /// # #![feature(collections)]
244 /// use std::collections::BitSet;
246 /// let mut s = BitSet::new();
247 /// s.reserve_len(10);
248 /// assert!(s.capacity() >= 10);
250 pub fn reserve_len(&mut self, len: usize) {
251 let cur_len = self.bit_vec.len();
253 self.bit_vec.reserve(len - cur_len);
257 /// Reserves the minimum capacity for the given `BitSet` to contain `len` distinct elements.
258 /// In the case of `BitSet` this means reallocations will not occur as long as all inserted
259 /// elements are less than `len`.
261 /// Note that the allocator may give the collection more space than it requests. Therefore
262 /// capacity can not be relied upon to be precisely minimal. Prefer `reserve_len` if future
263 /// insertions are expected.
269 /// # #![feature(collections)]
270 /// use std::collections::BitSet;
272 /// let mut s = BitSet::new();
273 /// s.reserve_len_exact(10);
274 /// assert!(s.capacity() >= 10);
276 pub fn reserve_len_exact(&mut self, len: usize) {
277 let cur_len = self.bit_vec.len();
279 self.bit_vec.reserve_exact(len - cur_len);
284 /// Consumes this set to return the underlying bit vector.
289 /// # #![feature(collections)]
290 /// use std::collections::BitSet;
292 /// let mut s = BitSet::new();
296 /// let bv = s.into_bit_vec();
301 pub fn into_bit_vec(self) -> BitVec<B> {
305 /// Returns a reference to the underlying bit vector.
310 /// # #![feature(collections)]
311 /// use std::collections::BitSet;
313 /// let mut s = BitSet::new();
316 /// let bv = s.get_ref();
317 /// assert_eq!(bv[0], true);
320 pub fn get_ref(&self) -> &BitVec<B> {
325 fn other_op<F>(&mut self, other: &Self, mut f: F) where F: FnMut(B, B) -> B {
327 let self_bit_vec = &mut self.bit_vec;
328 let other_bit_vec = &other.bit_vec;
330 let self_len = self_bit_vec.len();
331 let other_len = other_bit_vec.len();
333 // Expand the vector if necessary
334 if self_len < other_len {
335 self_bit_vec.grow(other_len - self_len, false);
338 // virtually pad other with 0's for equal lengths
340 let (_, result) = match_words(self_bit_vec, other_bit_vec);
344 // Apply values found in other
345 for (i, w) in other_words {
346 let old = self_bit_vec.storage()[i];
349 self_bit_vec.storage_mut()[i] = new;
354 /// Truncates the underlying vector to the least length required.
359 /// # #![feature(collections)]
360 /// use std::collections::BitSet;
362 /// let mut s = BitSet::new();
363 /// s.insert(32183231);
364 /// s.remove(&32183231);
366 /// // Internal storage will probably be bigger than necessary
367 /// println!("old capacity: {}", s.capacity());
369 /// // Now should be smaller
370 /// s.shrink_to_fit();
371 /// println!("new capacity: {}", s.capacity());
374 pub fn shrink_to_fit(&mut self) {
375 let bit_vec = &mut self.bit_vec;
376 // Obtain original length
377 let old_len = bit_vec.storage().len();
378 // Obtain coarse trailing zero length
379 let n = bit_vec.storage().iter().rev().take_while(|&&n| n == B::zero()).count();
381 let trunc_len = cmp::max(old_len - n, 1);
383 bit_vec.storage_mut().truncate(trunc_len);
384 bit_vec.set_len(trunc_len * B::bits());
388 /// Iterator over each usize stored in the `BitSet`.
393 /// # #![feature(collections)]
394 /// use std::collections::{BitVec, BitSet};
396 /// let s = BitSet::from_bit_vec(BitVec::from_bytes(&[0b01001010]));
398 /// // Print 1, 4, 6 in arbitrary order
399 /// for x in s.iter() {
400 /// println!("{}", x);
404 pub fn iter(&self) -> Iter<B> {
405 Iter(BlockIter::from_blocks(self.bit_vec.blocks()))
408 /// Iterator over each usize stored in `self` union `other`.
409 /// See [union_with](#method.union_with) for an efficient in-place version.
414 /// # #![feature(collections)]
415 /// use std::collections::{BitVec, BitSet};
417 /// let a = BitSet::from_bit_vec(BitVec::from_bytes(&[0b01101000]));
418 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[0b10100000]));
420 /// // Print 0, 1, 2, 4 in arbitrary order
421 /// for x in a.union(&b) {
422 /// println!("{}", x);
426 pub fn union<'a>(&'a self, other: &'a Self) -> Union<'a, B> {
427 fn or<B: BitBlock>(w1: B, w2: B) -> B { w1 | w2 }
429 Union(BlockIter::from_blocks(TwoBitPositions {
430 set: self.bit_vec.blocks(),
431 other: other.bit_vec.blocks(),
436 /// Iterator over each usize stored in `self` intersect `other`.
437 /// See [intersect_with](#method.intersect_with) for an efficient in-place version.
442 /// # #![feature(collections)]
443 /// use std::collections::{BitVec, BitSet};
445 /// let a = BitSet::from_bit_vec(BitVec::from_bytes(&[0b01101000]));
446 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[0b10100000]));
449 /// for x in a.intersection(&b) {
450 /// println!("{}", x);
454 pub fn intersection<'a>(&'a self, other: &'a Self) -> Intersection<'a, B> {
455 fn bitand<B: BitBlock>(w1: B, w2: B) -> B { w1 & w2 }
456 let min = cmp::min(self.bit_vec.len(), other.bit_vec.len());
458 Intersection(BlockIter::from_blocks(TwoBitPositions {
459 set: self.bit_vec.blocks(),
460 other: other.bit_vec.blocks(),
465 /// Iterator over each usize stored in the `self` setminus `other`.
466 /// See [difference_with](#method.difference_with) for an efficient in-place version.
471 /// # #![feature(collections)]
472 /// use std::collections::{BitSet, BitVec};
474 /// let a = BitSet::from_bit_vec(BitVec::from_bytes(&[0b01101000]));
475 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[0b10100000]));
477 /// // Print 1, 4 in arbitrary order
478 /// for x in a.difference(&b) {
479 /// println!("{}", x);
482 /// // Note that difference is not symmetric,
483 /// // and `b - a` means something else.
485 /// for x in b.difference(&a) {
486 /// println!("{}", x);
490 pub fn difference<'a>(&'a self, other: &'a Self) -> Difference<'a, B> {
491 fn diff<B: BitBlock>(w1: B, w2: B) -> B { w1 & !w2 }
493 Difference(BlockIter::from_blocks(TwoBitPositions {
494 set: self.bit_vec.blocks(),
495 other: other.bit_vec.blocks(),
500 /// Iterator over each usize stored in the symmetric difference of `self` and `other`.
501 /// See [symmetric_difference_with](#method.symmetric_difference_with) for
502 /// an efficient in-place version.
507 /// # #![feature(collections)]
508 /// use std::collections::{BitSet, BitVec};
510 /// let a = BitSet::from_bit_vec(BitVec::from_bytes(&[0b01101000]));
511 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[0b10100000]));
513 /// // Print 0, 1, 4 in arbitrary order
514 /// for x in a.symmetric_difference(&b) {
515 /// println!("{}", x);
519 pub fn symmetric_difference<'a>(&'a self, other: &'a Self) -> SymmetricDifference<'a, B> {
520 fn bitxor<B: BitBlock>(w1: B, w2: B) -> B { w1 ^ w2 }
522 SymmetricDifference(BlockIter::from_blocks(TwoBitPositions {
523 set: self.bit_vec.blocks(),
524 other: other.bit_vec.blocks(),
529 /// Unions in-place with the specified other bit vector.
534 /// # #![feature(collections)]
535 /// use std::collections::{BitSet, BitVec};
537 /// let a = 0b01101000;
538 /// let b = 0b10100000;
539 /// let res = 0b11101000;
541 /// let mut a = BitSet::from_bit_vec(BitVec::from_bytes(&[a]));
542 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[b]));
543 /// let res = BitSet::from_bit_vec(BitVec::from_bytes(&[res]));
545 /// a.union_with(&b);
546 /// assert_eq!(a, res);
549 pub fn union_with(&mut self, other: &Self) {
550 self.other_op(other, |w1, w2| w1 | w2);
553 /// Intersects in-place with the specified other bit vector.
558 /// # #![feature(collections)]
559 /// use std::collections::{BitSet, BitVec};
561 /// let a = 0b01101000;
562 /// let b = 0b10100000;
563 /// let res = 0b00100000;
565 /// let mut a = BitSet::from_bit_vec(BitVec::from_bytes(&[a]));
566 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[b]));
567 /// let res = BitSet::from_bit_vec(BitVec::from_bytes(&[res]));
569 /// a.intersect_with(&b);
570 /// assert_eq!(a, res);
573 pub fn intersect_with(&mut self, other: &Self) {
574 self.other_op(other, |w1, w2| w1 & w2);
577 /// Makes this bit vector the difference with the specified other bit vector
583 /// # #![feature(collections)]
584 /// use std::collections::{BitSet, BitVec};
586 /// let a = 0b01101000;
587 /// let b = 0b10100000;
588 /// let a_b = 0b01001000; // a - b
589 /// let b_a = 0b10000000; // b - a
591 /// let mut bva = BitSet::from_bit_vec(BitVec::from_bytes(&[a]));
592 /// let bvb = BitSet::from_bit_vec(BitVec::from_bytes(&[b]));
593 /// let bva_b = BitSet::from_bit_vec(BitVec::from_bytes(&[a_b]));
594 /// let bvb_a = BitSet::from_bit_vec(BitVec::from_bytes(&[b_a]));
596 /// bva.difference_with(&bvb);
597 /// assert_eq!(bva, bva_b);
599 /// let bva = BitSet::from_bit_vec(BitVec::from_bytes(&[a]));
600 /// let mut bvb = BitSet::from_bit_vec(BitVec::from_bytes(&[b]));
602 /// bvb.difference_with(&bva);
603 /// assert_eq!(bvb, bvb_a);
606 pub fn difference_with(&mut self, other: &Self) {
607 self.other_op(other, |w1, w2| w1 & !w2);
610 /// Makes this bit vector the symmetric difference with the specified other
611 /// bit vector in-place.
616 /// # #![feature(collections)]
617 /// use std::collections::{BitSet, BitVec};
619 /// let a = 0b01101000;
620 /// let b = 0b10100000;
621 /// let res = 0b11001000;
623 /// let mut a = BitSet::from_bit_vec(BitVec::from_bytes(&[a]));
624 /// let b = BitSet::from_bit_vec(BitVec::from_bytes(&[b]));
625 /// let res = BitSet::from_bit_vec(BitVec::from_bytes(&[res]));
627 /// a.symmetric_difference_with(&b);
628 /// assert_eq!(a, res);
631 pub fn symmetric_difference_with(&mut self, other: &Self) {
632 self.other_op(other, |w1, w2| w1 ^ w2);
636 /// Moves all elements from `other` into `Self`, leaving `other` empty.
641 /// # #![feature(collections, bit_set_append_split_off)]
642 /// use std::collections::{BitVec, BitSet};
644 /// let mut a = BitSet::new();
648 /// let mut b = BitSet::new();
653 /// a.append(&mut b);
655 /// assert_eq!(a.len(), 4);
656 /// assert_eq!(b.len(), 0);
657 /// assert_eq!(a, BitSet::from_bit_vec(BitVec::from_bytes(&[0b01110010])));
659 pub fn append(&mut self, other: &mut Self) {
660 self.union_with(other);
664 /// Splits the `BitSet` into two at the given key including the key.
665 /// Retains the first part in-place while returning the second part.
670 /// # #![feature(collections, bit_set_append_split_off)]
671 /// use std::collections::{BitSet, BitVec};
672 /// let mut a = BitSet::new();
678 /// let b = a.split_off(3);
680 /// assert_eq!(a.len(), 2);
681 /// assert_eq!(b.len(), 2);
682 /// assert_eq!(a, BitSet::from_bit_vec(BitVec::from_bytes(&[0b01100000])));
683 /// assert_eq!(b, BitSet::from_bit_vec(BitVec::from_bytes(&[0b00010010])));
685 pub fn split_off(&mut self, at: usize) -> Self {
686 let mut other = BitSet::new();
689 swap(self, &mut other);
691 } else if at >= self.bit_vec.len() {
695 // Calculate block and bit at which to split
696 let w = at / u32::BITS;
697 let b = at % u32::BITS;
699 // Pad `other` with `w` zero blocks,
700 // append `self`'s blocks in the range from `w` to the end to `other`
701 other.bit_vec.storage_mut().extend(repeat(0u32).take(w)
702 .chain(self.bit_vec.storage()[w..].iter().cloned()));
703 other.bit_vec.nbits = self.bit_vec.nbits;
706 other.bit_vec.storage_mut()[w] &= !0 << b;
709 // Sets `bit_vec.len()` and fixes the last block as well
710 self.bit_vec.truncate(at);
716 /// Returns the number of set bits in this set.
718 pub fn len(&self) -> usize {
719 self.bit_vec.blocks().fold(0, |acc, n| acc + n.count_ones() as usize)
722 /// Returns whether there are no bits set in this set
724 pub fn is_empty(&self) -> bool {
728 /// Clears all bits in this set
730 pub fn clear(&mut self) {
731 self.bit_vec.clear();
734 /// Returns `true` if this set contains the specified integer.
736 pub fn contains(&self, value: &usize) -> bool {
737 let bit_vec = &self.bit_vec;
738 *value < bit_vec.len() && bit_vec[*value]
741 /// Returns `true` if the set has no elements in common with `other`.
742 /// This is equivalent to checking for an empty intersection.
744 pub fn is_disjoint(&self, other: &Self) -> bool {
745 self.intersection(other).next().is_none()
748 /// Returns `true` if the set is a subset of another.
750 pub fn is_subset(&self, other: &Self) -> bool {
751 let self_bit_vec = &self.bit_vec;
752 let other_bit_vec = &other.bit_vec;
753 let other_blocks = blocks_for_bits::<B>(other_bit_vec.len());
755 // Check that `self` intersect `other` is self
756 self_bit_vec.blocks().zip(other_bit_vec.blocks()).all(|(w1, w2)| w1 & w2 == w1) &&
757 // Make sure if `self` has any more blocks than `other`, they're all 0
758 self_bit_vec.blocks().skip(other_blocks).all(|w| w == B::zero())
761 /// Returns `true` if the set is a superset of another.
763 pub fn is_superset(&self, other: &Self) -> bool {
764 other.is_subset(self)
767 /// Adds a value to the set. Returns `true` if the value was not already
768 /// present in the set.
769 pub fn insert(&mut self, value: usize) -> bool {
770 if self.contains(&value) {
774 // Ensure we have enough space to hold the new element
775 let len = self.bit_vec.len();
777 self.bit_vec.grow(value - len + 1, false)
780 self.bit_vec.set(value, true);
784 /// Removes a value from the set. Returns `true` if the value was
785 /// present in the set.
786 pub fn remove(&mut self, value: &usize) -> bool {
787 if !self.contains(value) {
791 self.bit_vec.set(*value, false);
797 impl<B: BitBlock> fmt::Debug for BitSet<B> {
798 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
799 try!(write!(fmt, "{{"));
800 let mut first = true;
803 try!(write!(fmt, ", "));
805 try!(write!(fmt, "{:?}", n));
812 impl<B: BitBlock> hash::Hash for BitSet<B> {
813 fn hash<H: hash::Hasher>(&self, state: &mut H) {
821 struct BlockIter<T, B> {
827 impl<T, B: BitBlock> BlockIter<T, B> where T: Iterator<Item=B> {
828 fn from_blocks(mut blocks: T) -> BlockIter<T, B> {
829 let h = blocks.next().unwrap_or(B::zero());
830 BlockIter {tail: blocks, head: h, head_offset: 0}
834 /// An iterator combining two `BitSet` iterators.
836 struct TwoBitPositions<'a, B: 'a> {
838 other: Blocks<'a, B>,
839 merge: fn(B, B) -> B,
842 /// An iterator for `BitSet`.
844 pub struct Iter<'a, B: 'a>(BlockIter<Blocks<'a, B>, B>);
846 pub struct Union<'a, B: 'a>(BlockIter<TwoBitPositions<'a, B>, B>);
848 pub struct Intersection<'a, B: 'a>(Take<BlockIter<TwoBitPositions<'a, B>, B>>);
850 pub struct Difference<'a, B: 'a>(BlockIter<TwoBitPositions<'a, B>, B>);
852 pub struct SymmetricDifference<'a, B: 'a>(BlockIter<TwoBitPositions<'a, B>, B>);
854 impl<'a, T, B: BitBlock> Iterator for BlockIter<T, B> where T: Iterator<Item=B> {
857 fn next(&mut self) -> Option<usize> {
858 while self.head == B::zero() {
859 match self.tail.next() {
860 Some(w) => self.head = w,
863 self.head_offset += B::bits();
866 // from the current block, isolate the
867 // LSB and subtract 1, producing k:
868 // a block with a number of set bits
869 // equal to the index of the LSB
870 let k = (self.head & (!self.head + B::one())) - B::one();
871 // update block, removing the LSB
872 self.head = self.head & (self.head - B::one());
873 // return offset + (index of LSB)
874 Some(self.head_offset + (B::count_ones(k) as usize))
878 fn size_hint(&self) -> (usize, Option<usize>) {
879 match self.tail.size_hint() {
880 (_, Some(h)) => (0, Some(1 + h * B::bits())),
886 impl<'a, B: BitBlock> Iterator for TwoBitPositions<'a, B> {
889 fn next(&mut self) -> Option<B> {
890 match (self.set.next(), self.other.next()) {
891 (Some(a), Some(b)) => Some((self.merge)(a, b)),
892 (Some(a), None) => Some((self.merge)(a, B::zero())),
893 (None, Some(b)) => Some((self.merge)(B::zero(), b)),
899 fn size_hint(&self) -> (usize, Option<usize>) {
900 let (a, au) = self.set.size_hint();
901 let (b, bu) = self.other.size_hint();
903 let upper = match (au, bu) {
904 (Some(au), Some(bu)) => Some(cmp::max(au, bu)),
908 (cmp::max(a, b), upper)
912 impl<'a, B: BitBlock> Iterator for Iter<'a, B> {
915 #[inline] fn next(&mut self) -> Option<usize> { self.0.next() }
916 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() }
919 impl<'a, B: BitBlock> Iterator for Union<'a, B> {
922 #[inline] fn next(&mut self) -> Option<usize> { self.0.next() }
923 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() }
926 impl<'a, B: BitBlock> Iterator for Intersection<'a, B> {
929 #[inline] fn next(&mut self) -> Option<usize> { self.0.next() }
930 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() }
933 impl<'a, B: BitBlock> Iterator for Difference<'a, B> {
936 #[inline] fn next(&mut self) -> Option<usize> { self.0.next() }
937 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() }
940 impl<'a, B: BitBlock> Iterator for SymmetricDifference<'a, B> {
943 #[inline] fn next(&mut self) -> Option<usize> { self.0.next() }
944 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.0.size_hint() }
947 impl<'a, B: BitBlock> IntoIterator for &'a BitSet<B> {
949 type IntoIter = Iter<'a, B>;
951 fn into_iter(self) -> Iter<'a, B> {