[Dylan16807]

But IEEE 754 works as you described in your last comment. It doesn't take the numerator's sign. So what's wrong?

Can you give more context on your voltage math? Was the numerator sometimes negative? If the problem is that your divisor calculation sometimes resulted in positive zero, that doesn't sound like the standard being wrong without more info.

[dmoy]

> But IEEE 754 works as you described in your last comment. It doesn't take the numerator's sign. So what's wrong?

The numerator was always positive. The denominator was always negative (negative voltage is a pretty common thing), except when it became zero. That led to surprising behavior.

Right the whole point of the exercise was that sometimes the standard is wrong for your specific problem at hand. We spent lecture after lecture going over exactly how ieee754 precision loss worked, and other edge cases, so we could know how to exactly follow the standard.

Then we had an example where the sudden sign flip from a/-0.00000000001 = <huge_negative_number> to a/0 = <positive_infinity> would cause big problems with a calculation. If you didn't explicitly handle the divide by zero case and do the "correct for domain, but not following ieee754 standard" way, then you'd fry a component.

It's been a long time so I don't remember the exact setup, just the higher level lesson of "don't blindly follow standards and assume you don't need to check edge cases (exception or otherwise) because the standard does things a certain way".

[Dylan16807]

It's a good lesson in defensiveness! But if your value was always either less than zero or negative zero it would have done the right thing, both domain correct and standard correct. It's hard to say exactly why you got positive zero, but my bet is that it's more subtle than the standard doing something you can actually call "wrong".