[Tutor] Variable Swap

[Steve Nelson]

On 1/29/07, Kent Johnson <kent37 at tds.net> wrote:
> Because 2 ^ 3 == 1, right? Are you sure you understand what xor does? It
> is a bitwise exclusive or:

Yes... at a binary level, it returns true if either input is true, but not both:

A B Q
0 0 0
0 1 1
1 0 1
1 1 0

Thus it has the effect of swapping / reversing.

For some reason I had not been thinking straight, and had thought we
might just see a toggle of the value of the variable, which is, of
course, nonsense.

So in my example:

2 = 00000010
3 = 00000011

xor:

Q = 00000001

Lesson: think first... was just me being blind.

> x, y = y, x

Doesn't this use temporary variables?

> Kent

S.