The &= Operator Equivalent

Question

Consider the following code:

bool funcExecuted = false;
bool result = false;
Func<bool> returnFalse = () =>
{
    funcExecuted = true;
    return false; 
};
result &= returnFalse();

string msg = funcExecuted?"Executed":"Not Executed";
Console.WriteLine(msg);

Expected result:

• I expected to get the message of Not Executed

Actual result:

• I got the Executed message.

Conclusions:

result &= returnFalse(); is compiled to result = result & returnFalse(); rather than result = result && returnFalse(); (I expected the latter).

My question is, why is that?

I would expect it to be the other way around. We all use the && operator much more commonly than the & operator and I would expect it to be the "default behaviour".

---

Update: Most answers seems to answer the wrong question.
I am aware of the fact that the difference between && and & is that && is short-circuiting, whereas & always evaluates both operands.

The question was why does a &= b translates into a = a & b; rather than a = a && b;

Answer 1

The confusion that you fail into is that when there is a difference when you use && and & on numeric values but there is not when you use it on booleans in context of bytes.

Then only difference is that when you use &&, you get as short-circuiting.

boolean result = false  & true; //bitwise AND
boolean result = false && true; //logical AND

There is no difference in result. Then only difference is how CPU will deal with it.

In that case when you are using operator &= for boolean it is equal to use result = value & value.

The assumption that short-circuiting, will be used when you use &= is not easy to understand. The argument that && is used more often than & does not find place here. Because the & is bitwise logical operator and && is logical. So it is natural that &= mean what it mean.

Answer 2

You got "Executed" message because of

Func<bool> returnFalse = () =>
{
    funcExecuted = true; //THIS !!!!!!
    return false; 
};

and this

string msg = funcExecuted?"Executed":"Not Executed";

funcExceuted is ALWAYS (in the scope of provided code) true.

The code of binary & you wrote is actually converted to what you expect:

result &= returnFalse(); 

is

result = result &  returnFalse();

but the thing is that on condition you don't check for result, but for funcExceuted. change it ti result and you will get expected behavior from code.

What about

why is that?

it's C# language syntax, for the same reson

left+=right is converted to left = left + right

Answer 3

One of the key differences between && and & is that && is short-circuiting, whereas & always evaluates both operands.

The result &= returnFalse(); is eqivalent to result = result & returnFalse();.