std::bitset + Reading Assignment Week 9

Simulates working with binary in C++.

In computing, a flag is a value that signals when some condition exists in a program. With a bit flag, a value of true means the condition exists.


<bitset> // for std::bitset

std:: bitset<8> mybitset {}; // 8 bits in size means room for 8 flags.

Manipulating bits via std::bitset

std::bitset not only print values in binary, it can also...

.test() -- allows us to query whether a bit is a 0 or 1
.set() -- allows us to turn a bit on (will do nothing if the bit is already on)
.reset() -- allows us to turn a bit off (^ above parentheses)
.flip() -- allows us to flip a bit value from a 0 to a 1 or vice versa.

Each of these functions takes the position of the bit we want to operate on as their only argument.


#include <bitset>
#include <iostream>

using namespace std;

int main() {
    bitset<8> bits { 0b000'0101 }; // we need 8 bits, start with bit pattern 0000 0101
    
    cout << "Start: " << bits << '\n';
    cout << "bits.set(3): " << bits.set(3) << '\n';
    cout << "bits.flip(4): " << bits.flip(4) << '\n';
    cout << "bits.reset(4): " << bits.reset(4) << '\n'; // sets bit 4 back to 0
    cout << "bit 3 has value of: " << bits.test(3) << '\n';
    cout << "bitset indexing goes from right to left.";


    return 0;
}

Output:


Start: 00000101
bits.set(3): 00001101
bits.flip(4): 00011101
bits.reset(4): 00001101
bit 3 has value of: 1
bitset indexing goes from right to left.

Note: Normal functions are called like this: function(object). With member functions, we call object.function().

Querying std::bitset

.size() returns the number of bits in the bitset.
.count() returns the number of bits in the bitset that are set to true.
.all() returns a Boolean indicating whether all bits are set to true.
.any() returns a Boolean indicating whether any bits are set to true.
.none() returns a Boolean indicating whether no bits are set to true.


    bitset<8> bits { 0b000'1101 };
    cout << bits.size() << " bits are in the bitset\n";
    cout << bits.count() << " bits are set to true\n";

    cout << boolalpha; // changes how boolean values are printed to the console.
    cout << "All bits are true: " << bits.all() << '\n';
    cout << "Some bits are true: " << bits.any() << '\n';
    cout << "No bits are true: " << bits.none() << '\n';

Output:


8 bits are in the bitset
3 bits are set to true
All bits are true: false
Some bits are true: true
No bits are true: false