# using xor for signedness

When multiplying or diving 2 numbers, determining the signedness of the result is not straightforward:

```
1 a = -1
2 b = 2
3 sign = 1 if a * b > 0 else -1
```

Here we are actually going ahead and actually performing the multiplication. If we do not want to do so, then things get even more complicated:

```
1 a = -1
2 b = 2
3 sign = 1
4 if a > 0 and b > 0:
5 sign = 1
6 elif a < 0 and b < 0:
7 sign = 1
8 elif a > 0 and b < 0:
9 sign = -1
10 elif a < 0 and b > 0:
11 sign = -1
```

However you may notice that signedness of two numbers follows the same rules as xoring two bits, therefore the most efficient and simplest method is:

```
1 a = -1
2 b = 2
3 sign = -1 if (a < 0) ^ (b < 0) else 1
```