alt Hacker NewsThe XOR trick is only cool in its undefined-behavior form:
a^=b^=a^=b;
Which allegedly saves you 0.5 seconds of typing in competitive programming competitions from 20 years ago and is known to work reliably (on MinGW under Windows XP).
Bonus authenticity: use `a^=a` to zero a register in a single x86 instruction (and makes a real difference for compiler toolchains 30+ years old).
For real now, a very useful application of XOR is its relation to the Nim game [0], which comes in very handy if you need to save your village from an ancient disgruntled Chinese emperor.
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> The XOR trick is only cool in its undefined-behavior form:
> a^=b^=a^=b;
I believe this is defined in C++ since C++17, but still undefined in C.
>Bonus authenticity: use `a^=a` to zero a register in a single x86 instruction (and makes a real difference for compiler toolchains 30+ years old).
Modern compilers will still use xor for zeroing registers on their own.
For instance: https://godbolt.org/z/n5n35xjqx
Variable a(register esi) is first initialized to 42 with mov and then cleared to zero using xor.
`xor eax, eax` is less code when assembled. That's why compilers generate it.