C++ Bit Operators ~ - bitwise NOT (unary complement)
Example
unsigned char a = 234; // 1110 1010b (0xEA)
unsigned char b = ~a; // 0001 0101b (0x15)
std::cout << "a = " << static_cast<int>(a) <<
", b = " << static_cast<int>(b) << std::endl;
Output
a = 234, b = 21
Why
A bit wise NOT (unary complement) operates on the bit level and simply flips each bit. If it's a 1, it's changed to a 0, if it's a 0, it's changed to a 1. The bit wise NOT has the same effect as XOR'ing a value against the max value for a specific type:
unsigned char a = 234; // 1110 1010b (0xEA)
unsigned char b = ~a; // 0001 0101b (0x15)
unsigned char c = a ^ ~0;
The bit wise NOT can also be a convenient way to check the maximum value for a specific integral type:
unsigned int i = ~0;
unsigned char c = ~0;
std::cout << "max uint = " << i << std::endl <<
"max uchar = " << static_cast<short>(c) << std::endl;
The bit wise NOT does not change the value of the original value and does not have a compound assignment operator, so you can not do a ~= 10 for example.
The bit wise NOT (~) should not be confused with the logical NOT (!); where a bit wise NOT will flip each bit, a logical NOT will use the whole value to do its operation on, in other words (!1) != (~1)
