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263 lines
8.2 KiB
C++
263 lines
8.2 KiB
C++
//===-- BitVectorSet.h - A bit-vector representation of sets ----*- C++ -*-===//
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//
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// This is an implementation of the bit-vector representation of sets. Unlike
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// vector<bool>, this allows much more efficient parallel set operations on
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// bits, by using the bitset template. The bitset template unfortunately can
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// only represent sets with a size chosen at compile-time. We therefore use a
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// vector of bitsets. The maxmimum size of our sets (i.e., the size of the
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// universal set) can be chosen at creation time.
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//
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// External functions:
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//
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// bool Disjoint(const BitSetVector& set1, const BitSetVector& set2):
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// Tests if two sets have an empty intersection.
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// This is more efficient than !(set1 & set2).any().
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//
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//===----------------------------------------------------------------------===//
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#ifndef SUPPORT_BITSETVECTOR_H
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#define SUPPORT_BITSETVECTOR_H
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#include <bitset>
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#include <vector>
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#include <functional>
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#include <iostream>
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class BitSetVector {
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enum { BITSET_WORDSIZE = sizeof(long)*8 };
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// Types used internal to the representation
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typedef std::bitset<BITSET_WORDSIZE> bitword;
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typedef bitword::reference reference;
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class iterator;
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// Data used in the representation
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std::vector<bitword> bitsetVec;
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unsigned maxSize;
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private:
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// Utility functions for the representation
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static unsigned NumWords(unsigned Size) {
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return (Size+BITSET_WORDSIZE-1)/BITSET_WORDSIZE;
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}
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static unsigned LastWordSize(unsigned Size) { return Size % BITSET_WORDSIZE; }
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// Clear the unused bits in the last word.
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// The unused bits are the high (BITSET_WORDSIZE - LastWordSize()) bits
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void ClearUnusedBits() {
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unsigned long usedBits = (1U << LastWordSize(size())) - 1;
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bitsetVec.back() &= bitword(usedBits);
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}
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const bitword& getWord(unsigned i) const { return bitsetVec[i]; }
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bitword& getWord(unsigned i) { return bitsetVec[i]; }
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friend bool Disjoint(const BitSetVector& set1,
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const BitSetVector& set2);
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BitSetVector(); // do not implement!
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public:
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///
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/// Constructor: create a set of the maximum size maxSetSize.
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/// The set is initialized to empty.
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///
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BitSetVector(unsigned maxSetSize)
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: bitsetVec(NumWords(maxSetSize)), maxSize(maxSetSize) { }
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/// size - Return the number of bits tracked by this bit vector...
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unsigned size() const { return maxSize; }
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///
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/// Modifier methods: reset, set for entire set, operator[] for one element.
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///
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void reset() {
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for (unsigned i=0, N = bitsetVec.size(); i < N; ++i)
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bitsetVec[i].reset();
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}
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void set() {
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for (unsigned i=0, N = bitsetVec.size(); i < N; ++i) // skip last word
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bitsetVec[i].set();
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ClearUnusedBits();
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}
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reference operator[](unsigned n) {
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assert(n < size() && "BitSetVector: Bit number out of range");
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unsigned ndiv = n / BITSET_WORDSIZE, nmod = n % BITSET_WORDSIZE;
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return bitsetVec[ndiv][nmod];
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}
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iterator begin() { return iterator::begin(*this); }
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iterator end() { return iterator::end(*this); }
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///
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/// Comparison operations: equal, not equal
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///
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bool operator == (const BitSetVector& set2) const {
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assert(maxSize == set2.maxSize && "Illegal == comparison");
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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if (getWord(i) != set2.getWord(i))
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return false;
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return true;
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}
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bool operator != (const BitSetVector& set2) const {
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return ! (*this == set2);
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}
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///
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/// Set membership operations: single element, any, none, count
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///
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bool test(unsigned n) const {
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assert(n < size() && "BitSetVector: Bit number out of range");
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unsigned ndiv = n / BITSET_WORDSIZE, nmod = n % BITSET_WORDSIZE;
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return bitsetVec[ndiv].test(nmod);
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}
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bool any() const {
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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if (bitsetVec[i].any())
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return true;
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return false;
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}
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bool none() const {
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return ! any();
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}
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unsigned count() const {
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unsigned n = 0;
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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n += bitsetVec[i].count();
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return n;
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}
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bool all() const {
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return (count() == size());
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}
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///
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/// Set operations: intersection, union, disjoint union, complement.
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///
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BitSetVector operator& (const BitSetVector& set2) const {
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assert(maxSize == set2.maxSize && "Illegal intersection");
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BitSetVector result(maxSize);
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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result.getWord(i) = getWord(i) & set2.getWord(i);
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return result;
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}
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BitSetVector operator| (const BitSetVector& set2) const {
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assert(maxSize == set2.maxSize && "Illegal intersection");
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BitSetVector result(maxSize);
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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result.getWord(i) = getWord(i) | set2.getWord(i);
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return result;
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}
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BitSetVector operator^ (const BitSetVector& set2) const {
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assert(maxSize == set2.maxSize && "Illegal intersection");
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BitSetVector result(maxSize);
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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result.getWord(i) = getWord(i) ^ set2.getWord(i);
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return result;
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}
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BitSetVector operator~ () const {
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BitSetVector result(maxSize);
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for (unsigned i = 0; i < bitsetVec.size(); ++i)
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(result.getWord(i) = getWord(i)).flip();
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result.ClearUnusedBits();
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return result;
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}
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///
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/// Printing and debugging support
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///
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void print(std::ostream &O) const;
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void dump() const { print(std::cerr); }
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public:
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//
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// An iterator to enumerate the bits in a BitSetVector.
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// Eventually, this needs to inherit from bidirectional_iterator.
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// But this iterator may not be as useful as I once thought and
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// may just go away.
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//
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class iterator {
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unsigned currentBit;
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unsigned currentWord;
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BitSetVector* bitvec;
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iterator(unsigned B, unsigned W, BitSetVector& _bitvec)
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: currentBit(B), currentWord(W), bitvec(&_bitvec) { }
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public:
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iterator(BitSetVector& _bitvec)
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: currentBit(0), currentWord(0), bitvec(&_bitvec) { }
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iterator(const iterator& I)
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: currentBit(I.currentBit),currentWord(I.currentWord),bitvec(I.bitvec) { }
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iterator& operator=(const iterator& I) {
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currentWord = I.currentWord;
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currentBit = I.currentBit;
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bitvec = I.bitvec;
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return *this;
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}
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// Increment and decrement operators (pre and post)
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iterator& operator++() {
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if (++currentBit == BITSET_WORDSIZE)
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{ currentBit = 0; if (currentWord < bitvec->size()) ++currentWord; }
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return *this;
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}
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iterator& operator--() {
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if (currentBit == 0) {
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currentBit = BITSET_WORDSIZE-1;
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currentWord = (currentWord == 0)? bitvec->size() : --currentWord;
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}
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else
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--currentBit;
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return *this;
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}
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iterator operator++(int) { iterator copy(*this); ++*this; return copy; }
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iterator operator--(int) { iterator copy(*this); --*this; return copy; }
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// Dereferencing operators
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reference operator*() {
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assert(currentWord < bitvec->size() &&
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"Dereferencing iterator past the end of a BitSetVector");
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return bitvec->getWord(currentWord)[currentBit];
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}
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// Comparison operator
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bool operator==(const iterator& I) {
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return (I.bitvec == bitvec &&
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I.currentWord == currentWord && I.currentBit == currentBit);
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}
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protected:
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static iterator begin(BitSetVector& _bitvec) { return iterator(_bitvec); }
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static iterator end(BitSetVector& _bitvec) { return iterator(0,
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_bitvec.size(), _bitvec); }
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friend class BitSetVector;
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};
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};
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inline void BitSetVector::print(std::ostream& O) const
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{
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for (std::vector<bitword>::const_iterator
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I=bitsetVec.begin(), E=bitsetVec.end(); I != E; ++I)
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O << "<" << (*I) << ">" << (I+1 == E? "\n" : ", ");
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}
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inline std::ostream& operator<< (std::ostream& O, const BitSetVector& bset)
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{
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bset.print(O);
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return O;
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};
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///
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/// Optimized versions of fundamental comparison operations
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///
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inline bool Disjoint(const BitSetVector& set1,
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const BitSetVector& set2)
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{
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assert(set1.size() == set2.size() && "Illegal intersection");
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for (unsigned i = 0; i < set1.bitsetVec.size(); ++i)
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if ((set1.getWord(i) & set2.getWord(i)).any())
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return false;
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return true;
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}
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#endif
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