My assumption has been that the XOR trick was closer to a thought experiment or hypothetical. That is to say, no one would ever use it in practice, but by askin

My assumption has been that the XOR trick was closer to a thought experiment or hypothetical. That is to say, no one would ever use it in practice, but by asking an interviewee to walk through it shows they have a low-level understanding of how binary numbers work, bit-masking. For me it falls in the obfuscated-C quadrant for code. Performance implications aside, it's just not the kind of "self-documenting" code I like lying around in my sources. (And I'll take clarity of purpose over performance every day.)