Last week I talked about unary integer operators, including the ^ operator. A reader wrote back asking:

Can you think of an use case for ^x?

So today I’m going to answer this question!

No!

LOL

Not very satisfying, is it?

So I did some digging to find some examples. Note, none of these are my own examples. This is something most of us will never use. But it’s a good question nonetheless. So here are some real-world places I found it being used:

• Here’s an example from github.com/golang/protobuf, where according to comments, it’s used for C++ compatibility:

  // The C++ parser accepts large positive hex numbers that uses
  // two's complement arithmetic to represent negative numbers.
  // This feature is here for backwards compatibility with C++.
  if strings.HasPrefix(tok.value, "0x") {
  	if x, err := strconv.ParseUint(tok.value, 0, 32); err == nil {
  		return protoreflect.ValueOfInt32(int32(-(int64(^x) + 1))), nil
  	}
  }
  

• Here’s an example from a gameboy emulator:

  func (cpu *CPU) resetBit(bit uint8, reg RWByte) {
  	mask := ^uint8(1 << bit)
  	value := reg.Read()
  
  	reg.Write(value & mask)
  }
  

I also found references to a few other examples, mostly related to low-level protocol work, but didn’t find code examples to share.