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0 pointstialaramex2mo ago0 comments

Because Python decided that (for the usual New Jersey reason, simplicity of implementation) bool should just be an integer type the Liskov criterion comes into play. If we can X an integer and we've agreed bool is an integer => we can X a bool. That's not what booleans are but hey, it's sorta close and this was easier to implement.

So, can we add two bools together? Adding booleans together is nonsense, but we've said these are a kind of integer so sure, I guess True + True = 2 ? And this cascades into nonsense like ~True being a valid operation in Python and its result is true...

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unanimous2mo ago

Out of curiosity, I tried running `~True` in a Python 3.14.2 repl and got this output (the -2 is part of the output):

>>> ~True

<python-input-1>:1: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.

-2

tialaramexOP2mo ago

Yes, the article I was reading was about proposals to er, undeprecate this feature. Reasoning that well, sure it's obviously a footgun - but it works for integers and we've said bools are integers so...

__mharrison__2mo ago

This is actually useful in pandas. It enables asking questions like "what percent of cars get greater than 40mph?"

jcgl2mo ago

> So, can we add two bools together? Adding booleans together is nonsense, but we've said these are a kind of integer so sure, I guess True + True = 2 ? And this cascades into nonsense like ~True being a valid operation in Python and its result is true...

The bitwise negation is indeed janky and inaccurate, but True + True = 2 is absolutely a valid thing to say in boolean algebra. Addition mean "or", and multiplication means "and."

tialaramexOP2mo ago

> True + True = 2 is absolutely a valid thing to say in boolean algebra

Nope. The Boolean algebra only has two values, and it lacks the addition operation entirely.

jcgl2mo ago

I always remember learning that 2 was a legit enough way to represent the result of 1 + 1, but the internet seems to agree with you mostly. Though I contend that 1 + 1 = 2 is unambiguous, so is fine.

But multiplication and addition do work just fine for boolean arithmetic: https://en.wikipedia.org/wiki/Two-element_Boolean_algebra

tialaramexOP2mo ago

Huh, I learn something new, I was not aware of "Two element Boolean algebra" nor just how deep this particular rabbit hole goes.

It's fine that 1 + 1 = 2. That's just integer arithmetic. The problem is that the booleans are not "just integers" and so Python's choice to implement them as "just integers" while convenient for them has consequences that are... undesirable.

j / k navigate · click thread line to collapse

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unanimous2mo ago

Out of curiosity, I tried running `~True` in a Python 3.14.2 repl and got this output (the -2 is part of the output):

>>> ~True

-2

tialaramexOP2mo ago

__mharrison__2mo ago

This is actually useful in pandas. It enables asking questions like "what percent of cars get greater than 40mph?"

jcgl2mo ago

The bitwise negation is indeed janky and inaccurate, but True + True = 2 is absolutely a valid thing to say in boolean algebra. Addition mean "or", and multiplication means "and."

tialaramexOP2mo ago

> True + True = 2 is absolutely a valid thing to say in boolean algebra

Nope. The Boolean algebra only has two values, and it lacks the addition operation entirely.

jcgl2mo ago

I always remember learning that 2 was a legit enough way to represent the result of 1 + 1, but the internet seems to agree with you mostly. Though I contend that 1 + 1 = 2 is unambiguous, so is fine.

But multiplication and addition do work just fine for boolean arithmetic: https://en.wikipedia.org/wiki/Two-element_Boolean_algebra

tialaramexOP2mo ago

Huh, I learn something new, I was not aware of "Two element Boolean algebra" nor just how deep this particular rabbit hole goes.

j / k navigate · click thread line to collapse