### Perform XOR over symbollic expression

I have written the code for a function but rather than addition I want to perform XOR how can I do it.

current output of

```
a,b = LR('a','b',3)
LRinv(a,b,3)
```

is

```
(a + P1(b + P2(a + P1(b) + 2*P3(b + P2(a + P1(b)))) + P2(a + P1(b))) + P1(b) + 2*P3(b + P2(a + P1(b))), b + P2(a + P1(b) + 2*P3(b + P2(a + P1(b)))) + P2(a + P1(b)))
```

Rather it should be (a,b) if XORED.

Thanks is advance!!!

```
def LR(L,R,rounds):
if(type(L)==type(R)==type('a')):
R = var(R)
L = var(L)
for r in range(0,rounds):
perm = DeprecatedSFunction("P"+str(r+1),1)
temp = R
R = L.__xor__(perm(R))
L = temp
return(L,R)
def LRinv(L,R,rounds):
if(type(L)==type(R)==type('a')):
R = var(L)
L = var(R)
else:
temp = R
R = L
L = temp
for r in range(0,rounds):
perm = DeprecatedSFunction("P"+str(rounds-r),1)
temp = R
R = L.__xor__(perm(R))
L = temp
return(R,L)
```