xor with 3 values

Question

I need to do an xor conditional between 3 values, ie i need one of the three values to be true but not more than one and not none.

I thought i could use the xor ^ op

Answer 1

XOR is a binary operator, it can only be used on 2 values at a time. So when you do (true XOR true XOR true), it actually does ((true XOR true) XOR true)...

The inner (true XOR true) resolves to false because they're the same. With that resolved, the remainder is (false XOR true), which resolves to true.

It sounds like you're trying to be clever or super-efficient about matching your conditions. This would probably take me several minutes to puzzle out and then write a truth-table or test to make sure it treats all possible combinations correctly.

It is so much simpler to just count how many of them are true and do if (countTrues == 1). The reason for this is that it doesn't have significant overhead, and it is actually readable and understandable compared to a solution using only bit-twiddling (there are a couple other answers here that demonstrate it).