0
Newbie Member
a^=b is equivalent to a = a ^ b
0
Newbie Member
^= is a binary XOR assignment;

It seems to run really slow however...
I wrote 2 versions of the same sorting function, 1 using a temp variable and the other using this method. When i ran it on my P4 sort_xor took 24 seconds while sort_temp took 15.

Code:
```#include <stdio.h>
#include <stdlib.h>

#define SIZE 50000

void sort_xor(int *a, int size)
/* Sorts the terms of the given array into numerical order. */
{
bool stop = false;
while (!stop)
{
stop = true;
for(int i = 0; i < size - 1; i++)
if (a[i] > a[i + 1])
{
a[i] ^= a[i + 1] ^= a[i] ^= a[i + 1];
stop = false;
}
}
}

void sort_temp(int *a, int size)
/* Sorts the terms of the given array into numerical order. */
{
bool stop = false;
int temp;
while (!stop)
{
stop = true;
for(int i = 0; i < size - 1; i++)
if (a[i] > a[i + 1])
{
temp = a[i];
a[i] = a[i + 1];
a[i + 1] = temp;
stop = false;
}
}
}

int main()
{
int a[SIZE];
for (int i = 0; i < SIZE; i++)
a[i] = SIZE - i;
printf("Sorting with sort_xor...\n");                    /* I start timing here*/
sort_xor(a, SIZE);
printf("Finished Shorting with shor_xor.\n");            /* Stop here */
printf("Press any key to sort with sort_temp\n");

getchar();

for (int i = 0; i < SIZE; i++)
a[i] = SIZE - i;
printf("Sorting with sort_temp...\n");                   /* I start timing here*/
sort_temp(a, SIZE);
printf("Finished Shorting with shor_temp.\n");           /* Stop here */
}```
0
Newbie Member
Yes you are correct. and following is the reason...

analyze following assembly code

temp = x
mov eax,dword ptr [x]
mov dword ptr [temp],eax

x = y;
mov eax,dword ptr [y]
mov dword ptr [x],eax

y = temp;
mov eax,dword ptr [temp]
mov dword ptr [y],eax

6 mov instruction....

x ^= y ^= x ^= y;
mov eax,dword ptr [x]
xor eax,dword ptr [y]
mov dword ptr [x],eax
mov ecx,dword ptr [y]
xor ecx,dword ptr [x]
mov dword ptr [y],ecx
mov edx,dword ptr [x]
xor edx,dword ptr [y]
mov dword ptr [x],edx
6 Mov + 3 Xor
0
Light Poster
the below logic also works as follows for swapping of nos without external variable introduction
Code:
```main()
{
int a,b;
printf("enter the nos");
scanf("%d %d",&a,&b);
printf("nos before swapping a=%d ,b=%d", a,b);
a=a*b;
b=a/b;
a=a/b;
printf("nos after swapping  a=%d ,b=%d", a,b);
}```

Last edited by shabbir; 16Jul2007 at 20:17.. Reason: Code block