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Comment by Supermancho | Hacker News Reader

Ponylang.io - There is a similar operation (toward zero)

https://stdlib.ponylang.io/builtin-Integer/#div_unsafe

and, in Ponylang, i/0 usually results in 0.

I think this is a bit different. Pony's div is total, and in order to be total div by 0 is 0, which is not a particularly absurd idea.

That said, I do feel that Pony should have added a 'panic' concept and then forced actors to handle panics, but that's me.

> which is not a particularly absurd idea

It's not completely untenable, but it's still kinda janky. I've never heard of any mathematical argument that justifies division by zero yielding 0; contrast 0^0, which at least has an argument for yielding 1: http://mathscitech.org/articles/zero-to-zero-power

https://www.hillelwayne.com/post/divide-by-zero/

> I've never heard of any mathematical argument that justifies division by zero yielding 0

0/x = 0 for all x except zero; defining 0/0=0 removes that exception.

x/x = 1 for all x except 0; defining 0/0 = 1 removes that exception.

Split the difference, 0/0 = 0.5

It gets worse: differentiation would be 0/0 if you went straight to the limit rather than just approaching it, so 0/0 can be any differentiable function, not just a value.

(Caveat: I’m probably being slightly imprecise with my language here)

From programming perspective, there's nothing sufficiently preposterous in the idea of dividing by zero that would require bringing the whole world to a low-level halt just for attempting that by default. You tried to calculate the average value of what turned out to be an empty list? Go suffer the most severe exception, like the ones reserved for those reading from nonexistant memory.

Another common case is adjusting some value according to a spatial vector's magnitude, like normalizing a vector or scaling gravitational attraction according to the distance between two points.

In the majority of these cases the most reasonable answer is 0.

Maybe the best argument is that the average of zero items should be zero?

But then why should the average of zero items be zero? It still seems like just an arbitrary choice to me.

I think it's worth all getting on the same page on the fact that math is fake and stupid. If it's more useful for 0/0 to == 0, that's justification enough imo.

Toward zero is a fairly intuitive way to do it, I think. Intuitively, if a you were, say, discretizing a length (L) with a number of steps (n) of some size (d) and went for d=L/n, you might want to always end up with d*n <= L even if L is negative, right? Although, having an integer for d may not make sense, or you might want to take |L| beforehand anyway...

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