What is this operator: &=

Question

Can someone explain what is the operator &= for?

I searched, but I got only results with & or =.

Answer 1

a &= b;

Is the same as

a = a & b;

& is the "bitwise and operator", search for that.

Answer 2

In C#(and in most languages I think) its the bitwise assigment operator.

a &= b is equivalent of a = a & b

http://msdn.microsoft.com/en-us/library/e669ax02.aspx

Answer 3

If i remember correctly it biwise operation...for example it can be used with [Flags]Enum. It check if your flag variable has specific value.

Answer 4

It's a shorthand operator which allows you to collapse

a = a & b

into

a &= b

Apart from bitwise operations on integers, &= can be used on boolean values as well, allowing you to collapse

a = a && b

into

a &= b

However, in the case of logical operation, the expanded form is short-circuiting, while the latter collapsed form does not short-circuit.

Example:

let b() be a function that returns a value and also does stuff that affects the program's state

let a be a boolean that is false

if you do

a = a && b()

the short-circuit happens: since a is false there's no need to evaluate b (and the extra computation that might happen inside b() is skipped).

On the other hand, if you do

a &= b()

the short-circuit doesn't happen: b is evaluated in any case, even when a is false (and evaluating b() wouldn't change the logical outcome), thus any extra computation that might happen inside b() does get executed.

Answer 5

a &= b is equivalent to a = a & b

Answer 6

This

x &= y;

is equivalent to

x = x & y;

Note that & is the bitwise and operator.