C# bitwise equal bool operator

Question

Boolean in C# are 1 byte variables. And because bool are shortcuts for the Boolean class, I would expect that the &=, |= operations have been overridden to let them work with the boolean types but I'm not so sure about it. There is nothing like &&= or ||= to be used.

Here's my question, doing something like:

bool result = condition;
result &= condition1;
result &= condition2;

will work but is it just because the bool will be 00000000 for false and 00000001 for true or because underneath the bool class will use something like &&= and ||= when the previous are called? Is it actually safe to use the previous notations or is better to use

bool result = condition;
result = result && condition1;
result = result && condition2;

to avoid any strange behavior?

Please note that conditions could be something like A >= B or any other possible check that will return a bool.

Community · Accepted Answer · 2017-05-23 12:24:47Z

13

As far as I can read in this SO post, the only real difference between bitwise operators and logical operators on booleans is that the latter won't evaluate the right side operand if the left side operand is false.

That means that if you have two booleans, there won't be much difference. If you have two methods, the last one doesn't get executed using logical operators, but it does with binary operators.

edited May 23, 2017 at 12:24

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answered Jul 31, 2015 at 9:15

Patrick Hofman

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user1196549 Over a year ago

If the second operand is itself a Boolean expression, you can spare its evaluation. Anyway, the benefit needs to be confirmed by benchmarking.

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

Per the documentation (emphasis mine):

An expression using the &= assignment operator, such as

x &= y

is equivalent to

x = x & y

except that x is only evaluated once. The & operator performs a bitwise logical AND operation on integral operands and logical AND on bool operands.

And similar for |=.

edited Jun 20, 2020 at 9:12

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answered Jul 31, 2015 at 9:15

Charles Mager

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3 Comments

absoluteAquarian Over a year ago

This answer is misleading. &= and |= are still bitwise operations, even on boolean values; a &= b is not a shorthand for a = a && b. According to sharplab.io, they still use the and and or instructions – which is what's used for bitwise operations – whereas && and || use branching instructions to implement the short-circuiting behaviour.

Charles Mager Over a year ago

@absoluteAquarian the answer (the documentation) doesn’t suggest it’s shorthand for the short-circuiting versions?

absoluteAquarian Over a year ago

Apologies, I must have misread your answer. The point that I was trying to make is that the bitwise (&, |) and conditional (&&, ||) operators do not have the same behavior, and someone could have interpreted the answer as such.

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