Q: How can I swap two values without using a temporary?
A: The standard hoary old assembly language programmer's trick is:
a ^= b; b ^= a; a ^= b;But this sort of code has little place in modern, HLL programming. Temporary variables are essentially free, and the idiomatic code using three assignments, namely
int t = a; a = b; b = t;is not only clearer to the human reader, it is more likely to be recognized by the compiler and turned into the most-efficient code (e.g. perhaps even using an EXCH instruction). The latter code is obviously also amenable to use with pointers and floating-point values, unlike the XOR trick. See also questions 3.3b and 10.3.
Additional links: further reading