25 Lesson25 Notes.md

Lesson 25 - Working with Bit Flags Using STL

Bits can be an efficient way of storing settings and flags.

• The bitset class
• The vector<bool>

The bitset Class

std::bitset is the STL class designed for handling information in bits and bit flags. std::bitset is not an STL container class because it cannot resize itself.
To use class std::bitset, include header: #include <bitset>

Instantiating the std::bitset

std::bitset<4> fourBits;  // 4 bits initialized to 0000
std::bitset<5> fiveBits("10101");  // 5 bits 10101
std::bitset<6> sixBits(0b100001);  // C++14 binary literal
std::bitset<8> eightBits (255);  // 8 bits initialized to long int 255
std::bitset<8> eightBitsCopy(eightBits);

This number is fixed at compile time; it isn’t dynamic. You can’t insert more bits into a bitset like you did to a vector.

The prefix 0b or 0B tells the compiler that the following digits are a binary representation of an integer. This literal is new to C++ and introduced in C++14.

Useful Operators Featured in std::bitset

Member Functions of std::bitset

The vector<bool>

Just a vector of boolean type elements, besides the vector<bool> features the function flip() similar to the function of bitset<>::flip().
To use class std::vector<bool>, include header: #include <vector>.

Instantiating the vector<bool>

vector<bool> boolFlags1;
vector<bool> boolFlags{ true, true, false };
vector<bool> boolFlags2 (10, true);
vector<bool> boolFlags2Copy (boolFlags2);