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Comment by om2 | Hacker News Reader

- and + operators have the same precedence. And a similar bug is possible if the operators were the same (both -). So I’m not sure it’s right to blame this on operator precedence or mixed operators. It’s just that, ultimately, the “consume” needs to be subtracted, not added.

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Non-mixed always goes strictly left to right, regardless of the operator, which I haven't seen anywhere near as much struggling with.

But yes, I personally parenthesize `a-b-c` explicitly, because it's not worth it for me to read and wonder if parenthesizing order matters later. Costs less than a second to write, saves a second or ten each time I read it - that's an excellent tradeoff imo, and is a trivial pattern to follow.

(Associative operators are fine, obviously)

I agree with explicit parentheses but please be careful about assuming associativity! The risk when handling floating-point arithmetic in particular is that associativity breaks, and suddenly a + (b + c) does NOT equal (a + b) + c. Not only can these lead to unexpected and hard-to-trace failure patterns, but depending on the details, they also can introduce memory overflow/underflow vulnerabilities.

If you're going for bit-for-bit equivalence of float values, then even with a single operation you're relying on compiler flags, architecture, the phase of the moon... I'm hard-pressed to think of any memory safety issues though.

Yea, you're in a fairly special niche of programming if you're somewhere that truly matters, and you can't accept any valid order's output. In most general code, if that kind of precision matters, float is the wrong choice: use a bignum object and be exactly correct regardless of how you organized your code.

Which is a niche that exists, obviously. So it is absolutely true for some cases. But I would hope that any code that requires this is extremely clear about requiring it.

Didn't you just suffer from the same trap the parent was trying to avoid?

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