C++ "|=" assignment operator

Question

My question is, what is the "|=" for in C++? I get that they are bitwise operators but i dont understand what they do here:

gObj->Variable |= 0x1000000;

Also, what does the "&" operator mean in this case?

if ((gObj->Variable & 2) == 2)
{
    do stuff
}

http://stackoverflow.com/questions/562303/the-definitive-c-book-guide-and-list. http://en.wikipedia.org/wiki/C_operators. — Oliver Charlesworth, Jun 15 '12 at 20:56
They would be used like your example when you have different flags, all represented by one bit. The first sets a flag, the second checks a flag. — chris, Jun 15 '12 at 20:56
If you know they are bitwise operators why not simply look to one of the thousands of existing resources available to you (including this site)? — Ed S., Jun 15 '12 at 20:56

betabandido · Answer 1 · 2012-06-15T21:01:53.147

5

These are bitwise operations.

| stands for an OR operation and & stands for an AND operation.

x |= y

is equivalent to

x = x | y

It is very common to use these operations with hexadecimal values, since it is much easier and very much intuitive. For instance:

0x10 | 0x01 = 0x11
0x10 & 0x01 = 0x00
0x10 & 0x11 = 0x10

edited Jun 15 '12 at 21:01

answered Jun 15 '12 at 20:56

betabandido

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score 3 · Answer 2 · answered Jun 15 '12 at 20:55

3

I am no C++ expert, but I believe these are treated like += or *=. That is, it will bitwise OR the bits of that variable with the hex number you mentioned. Also, Variable & 2 is doing a bitwise AND with 10 (binary).

answered Jun 15 '12 at 20:55

BlackVegetable

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score 0 · Answer 3 · edited Jun 19 '12 at 15:58

0

It is bitwise or operator and above statement will set the first bit of the variable to 1.

edited Jun 19 '12 at 15:58

Peter DeWeese

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answered Jun 16 '12 at 08:33

Tariq Mehmood

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C++ "|=" assignment operator

3 Answers3