Swap 2 objects, without using a temporary variable [closed]

Question

There are two objects:

Object1, Object2

You can easily swap them by:

Object3 = Object1
Object1 = Object2
Object2 = Object3

However, you must solve this problem by using no temporary object and Object1 should be changed to Object 2. (and vice versa)

Answer 1

Python

I'll say it first.

object1, object2 = object2, object1

Answer 2

Mathematica

A standard feature:

a = 1; b = 2;
Print[a, " ", b];
{a, b} = {b, a};
Print[a, " ", b];

Output

(*
1 2

2 1
*)

Answer 3

PostScript

In PostScript, it's common to use the stack instead of named variables, so a simple

exch

would do the job. But if you have variables, you can do it like

/a 1 def
/b 2 def
/a b /b a def def

Answer 4

If you have access to the memory address of these objects, you can swap them by xor-ing their addresses.

// return 0 for success, 1 for error
int swap(void *object1, void *object2, int size)
{
    for (int i = 0; i < size; i++)
    {
        char *x = (char *)(object1 + i);
        char *y = (char *)(object2 + i);
        if (x == y)
            return 1;
        *x ^= *y;
        *y ^= *x;
        *x ^= *y;
    }
    return 0;
}

per dmckee suggestion for clarity

Answer 5

Perl

($object1, $object2) = ($object2, $object1);

Using Perl's list assertions feels like cheating, but it's a pretty common feature.

Answer 6

PHP

Objects / arrays / resources:

list($a, $b) = [$b, $a];

Integers / booleans / strings of equal length:

$a ^= $b ^= $a ^= $b;

Answer 7

Forth

swap

As i have to include more than 30 characters, here's a link to a Forth primer