Negative sum for ~bool?

Asked Dec 07 '21 at 09:13

Active Dec 07 '21 at 09:13

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I have a boolean array with 1 True. The sum is 1, as expected:

b=np.array(([True,False],[False,False]))
b.sum()

The inverse of b, has 3 True and the sum is 3, as expected:

a=~b
a.sum()

But the sum of ~b is negative 2:

~b.sum()

I'm sure there is a reason. Can someone enlighten me?

asked Dec 07 '21 at 09:13

Wesley Kitlasten

3

*"the sum of ~b is negative 2"* - no, the negation of the sum of b is negative 2, it matters where you apply the `~`, to `b` or to the sum. `~1` simply is `-2`. – luk2302 Dec 07 '21 at 09:17
1

https://stackoverflow.com/a/8305225/16343464 – mozway Dec 07 '21 at 09:18
1

Operator precedence: `~b.sum()` -> `~(b.sum())` -> `~(1)` -> `-2` – juanpa.arrivillaga Dec 07 '21 at 09:31

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