XOR operation

Yes, it results from bit property of number
a = 0
b = 1
a ^= b   // a = 0 ^ 1   = 1
b ^= a;  // b = 1 ^ 1 = 0
a ^= b;  // a = 1 ^ 0   = 1
result:
a = 1
b = 0

What really happens?

Variable A
a = a ^ b
a = a ^ b ^ ( b ^ a ^ b )
Usage count of a = 2. XOR value is 0, it disappears.
Usage count of b is 3, this value will be a result.


Variable B
b = b ^ a
b = b ^ (a ^ b)

Usage count of a = 1. this value will be a result
Usage count of b is 2, XOR value is 0, it disappears.