Is there XNOR (Logical biconditional) operator in C#?

c# boolean boolean-operations

64,906

Solution 1

XNOR is simply equality on booleans; use A == B.

This is an easy thing to miss, since equality isn't commonly applied to booleans. And there are languages where it won't necessarily work. For example, in C, any non-zero scalar value is treated as true, so two "true" values can be unequal. But the question was tagged c#, which has, shall we say, well-behaved booleans.

Note also that this doesn't generalize to bitwise operations, where you want 0x1234 XNOR 0x5678 == 0xFFFFBBB3 (assuming 32 bits). For that, you need to build up from other operations, like ~(A^B). (Note: ~, not !.)

Solution 2

XOR = A or B, but Not A & B or neither (Can't be equal [!=])
XNOR is therefore the exact oppoiste, and can be easily represented by == or ===.

However, non-boolean cases present problems, like in this example:

a = 5
b = 1

if (a == b){
...
}

instead, use this:

a = 5
b = 1

if((a && b) || (!a && !b)){
...
}

if(!(a || b) && (a && b)){
...
}

the first example will return false (5 != 1), but the second will return true (a[value?] and b[value?]'s values return the same boolean, true (value = not 0/there is a value)

the alt example is just the reversed (a || b) && !(a && b) (XOR) gate

Solution 3

No, You need to use !(A^B)

Though I suppose you could use operator overloading to make your own XNOR.

64,906

trailmax

tech.trailmax.info - My blog. I write about C# and ASP.Net MVC (and sometimes about other random stuff) hrnet.trailmax.info My other blog. There I write about a technology I have been exposed for longer than I wanted. And now I know too much about HR.Net. This is part of my consulting service.

Updated on July 08, 2022

Comments

trailmax almost 2 years
I'm new to C# and could not find XNOR operator to provide this truth table:
```
a  b    a XNOR b
----------------
T  T       T
T  F       F
F  T       F
F  F       T
```
Is there a specific operator for this? Or I need to use !(A^B)?
- mrivard almost 13 years
  
  This operator is more commonly known as == for boolean operands...
- sll almost 13 years
  
  @Magnus Hoff : nice very nice point!
- spender almost 13 years
  
  I think the phrase "can't see the wood for the trees" is highly appropriate here. Voting up because we've all been here once or twice ;)
- Kerrek SB almost 13 years
  
  Maybe the OP iz l33t k!d who wants to write awesome shellcodez and needs to somehow hide the comparison operation. It's a possibility...
- trailmax almost 13 years
  
  sorry, Kerrek, I'm not from that crowd. And spender is quite right here -)
- enzi about 5 years
  
  Just fell into the same hole twice. @spender's metaphor is spot on
sll almost 13 years

This is bitwise, not a logical
Griffin almost 13 years

I think the poster knows that as he's included it in his question.
trailmax almost 13 years

@sllev you almost got me, I had to double check it. In C# ^ is logical if operated on boolean. If operated on integral types, it is bitwise. Please see msdn.microsoft.com/en-us/library/zkacc7k1.aspx
sll almost 13 years

@trailmax: cool stuff, thanks for pointing on this! Really devil is in detail!
ivan_pozdeev over 9 years

In C, ! operator can be used to convert int's to "well-behaved" booleans: !a==!b.
trailmax about 7 years

only C# does not have === operator
Cookie over 6 years

none of this answer is correct, === the non-coercive operator is javascript and the double !! before a value in an evaluation is not valid in c# either
cramopy over 6 years

as already stated, c# does not have triple equal sign Operator.
Keith Thompson over 4 years

@ivan_pozdeev And !! (that's two logical "not" operators) normalizes any scalar value to 0 or 1.
Darkcoder over 4 years

=== is not a operatr in C#...(===) is used is JavaScript.