1	CS 211: Introduction to Computer Programming II Instructor: Brian M. Dennis Teaching Assistants: Tom Lechner, Bin Lin, Rachel Goldsborough http://www.cs.northwestern.edu/~bmd/cs211/
2	Binary Reping Sets int set = 0x5A; // Binary 0101 1010, decimal 90 // Integers in the set, 1 3 4 6 // Technically, can hold 32 integers // 0 to 31 // 0000 0000 0000 0000 0000 0000 0101 1010 // Another set int another_set = 0xdecafbad; // 1101 1110 1100 1010 1111 1011 1010 1101
3	Adding an Element int set = 0x5A; // Binary 0101 1010, decimal 90 // Adding a an integer d to the set // Left shift, bitwise or int d = 7; int mask = 1 << d; set = set \| mask; set \|= mask; set \|= 1 << d;
4	Membership Testing int set = 0x5A; // Binary 0101 1010, decimal 90 // Testing membership of int d in the set // Left shift, bitwise and int d = 7; int mask = 1 << d; int test = set & mask;
5	Deleting a Member int set = 0x5A; // Binary 0101 1010, decimal 90 // Deleting d from the set // Left shift, negate, bitwise and int d = 6; int mask = 1 << d; // mask = 0100 0000 mask = ~mask; // mask = 1011 1111 int test = set & mask;
6	Set Abstract Datatype #ifndef _SET_H_ #define _SET_H_ 1 class BitSet { public: BitSet(); void add(int d); void del(int d); bool is_member(int d); public: int bits; }; #endif
7	Set Abstract Datatype BitSet::BitSet() { bits = 0; } BitSet::add(int d) { int mask = 1 << d; bits \|= mask; }
8	Set Abstract Datatype BitSet::del() { int mask = 1 << d; mask = ~mask; bits &= mask; } bool BitSet::is_member(int d) { int mask = 1 << d; int test = bits & mask; test ? true : false; }
9	Set Abstract Datatype #include <ctime> #include <cstdlib> #include "BitSet.h" int main() { BitSet bit_set; for(int i = 0; i < 10; i++) { int d = rand() % 32; bit_set.add(d); } return 0; }
10	Set Abstract Datatype #include <ctime> #include <cstdlib> #include "BitSet.h" using namespace std; int main() { BitSet bit_set; srand(time(0)); for(int i = 0; i < 10; i++) { int d = rand() % 32; bit_set + d; // Wouldn't it be nice if } }
11	Set Abstract Datatype // Stuff elided #include <iostream> using namespace std; int main() { BitSet bit_set; // Stuff elided // Let's print out a bitset cout << "BitSet["; for (int j = 0; j < 32; j++) { if (bit_set.is_member(j)) { cout << j; } } cout << "]"; cout << endl; }
12	Set Abstract Datatype // Stuff elided #include <iostream> using namespace std; int main() { BitSet bit_set; // Stuff elided // Let's print out a bitset cout << bit_set << endl; // Wouldn't it be nice }
13	Operator Overloading // Stuff elided BitSet& operator+(BitSet& bs, int d) { bs.add(d); return bs; } int main() { BitSet bit_set; for(int i = 0; i < 10; i++) { int d = rand() % 32; bit_set + d; // Wouldn't it be nice if } }
14	Operator Overloading #ifndef _SET_H_ #define _SET_H_ 1 class BitSet { public: BitSet(); void add(int d); void delete(int d); bool is_member(int d); // Let's hook into C++'s syntax BitSet& operator+(int d); private: int bits; }; #endif
15	Operator Overloading BitSet::BitSet() { bits = 0; } BitSet::add(int d) { int mask = 1 << d; bits \|= mask; } BitSet& BitSet::operator+(int d) { add(d) return *this; }
16	Operator Overloading // Has to be a standalone function not member function ostream& operator<<(ostream& os, BitSet& bs) { int foo = 10; cin >> foo; return os; } int main() { BitSet bit_set; // Stuff elided // Let's print out a bitset cout << bit_set << end; // Wouldn't it be nice }
17	That’s a Wrap Takeaways Bits can represent sets Building an ADT on that representation Operator overloading Syntactic extension Reading 8.1 – 8.7