A sign in C++ I've never seen before: |=

Question

I have some code here:

case MONITORTYPE_WUXGA_SXGA_WXGA:
    bResult |= (var == enum1);
    bResult |= (var == enum2);

Now i know what its doin

Answer 1

| is the bitwise or Operator. a |= b is equal to a = a | b.

More on bitwise operations: http://en.m.wikipedia.org/wiki/Bitwise_operation

Answer 2

It's equivalent to:

bResult = bResult | (var == enum1);

Just like a += b means a = a + b, a |= b means a = a | b.

Answer 3

a |= b

is the same as

a = a | b

which is a bitwise OR operation.

Answer 4

It's a bitwise OR. It means the same as bResult = bResult | (value). In this case, it is setting bResult to true if var is either enum1 or enum2.

Answer 5

For most binary operators ♢ in C++ (except comparison operators, relational operators and boolean operators), there exists a corresponding compound assignment operator, ♢=.

That is, |= is simply the compound assignment operator for | which is bitwise or. Its use is completely equivalent to +=, *= etc. So

a |= b;
// is equivalent to
a = a | b;