swap two integers without using a tmp variable?

[Steve]

How do you rewrite the swap function without using a tmp variable in
the swap function????

int main()
{
int x = 3;
int y = 5;

// Passing by reference

cout << "Passed by reference, before" << endl;
cout << "x = " << x << " y = " << y << endl;

swap(x,y);

cout << "Passed by reference, after" << endl;
cout << "x = " << x << " y = " << y << endl;

return 0;
}

void swap(int &x, int &y)
{
int tmp;

tmp = x;
x = y;
y = tmp;
}

[puppet_sock]

pu*********@hotmail.com wrote in message news:<c7**************************@posting.google. com>...

Richard Herring <ju**@[127.0.0.1]> wrote in message news:<1m**************@baesystems.com>...

In message <97**************************@posting.google.com >, Steve
<ng*****@my-deja.com> writes

The xor solution was really elegant. I would not have thought about it
and never knew it could be done this way.
X XOR Y XOR Y = X (assign in y variable, cancel out both Y)
X XOR Y XOR X = Y (assign in x variable, cancel out both X)

And it DOESN'T WORK (no apologies for shouting) if X and Y are both
references to the same object. Don't do it!

Well... You *could* add a self-assignment guard.

Sometimes coders find themselves working on extremely limited hardware.
Like a smoke detector or something. And every variable is taking up
the very limited RAM that was only allowed by having an arm-wrestling
match with the comptroller and the accountant.

Downthread discussion makes it clear that I didn't make myself clear.

Code can go in ROM. ROM may be cheaper than RAM. (Lots of reasons
from power supply to temperature sensitivity etc. And it takes a
specialist compiler to accomplish.) A temp can't go in ROM.

Still, in situations where your RAM is *that* limited, probably
you code in assembler, and the discussion is moot.
Socks