[tialaramex]

The correct answer to someone who insists upon "proper addition" is 10/21 and for it to be annoyingly slow so that they learn to be sure if they really care about "proper addition" or are just being awkward.

If you mean how should the machine do that, it can find the least common multiple of 3 and 7 (which is 21) and then convert both fractions to be in that denominator, then simplify if possible. This is, as I said, annoyingly slow, but if you want "proper" answers that's what you got.

I wouldn't bother because I'm aware that _Almost All Real Numbers are Normal_ and so they're usually completely impossible to express in this fashion anyway and we should stop our foolish pretence that you can add non-integers together and expect to get "correct" answers just because it can be done for some easy cases.

[lucb1e]

I'm sorry but where did I insist upon proper addition? I'll annotate the parts of my post that might be mistaken for it:

> a replacement for the + operator in javascript because computers can't do proper addition (0.1+0.2!=0.3).

Just saying they can't do it (I edited this: first I said that JS doesn't do it properly, but I thought that was rather too narrow. I guess 'computers' is too broad again. Pick a name, you know what I mean)

> [an explanation of what worked for me some years ago] Then you have arbitrary size and decimals with perfect addition (no floating point approximations anymore).

Again, just mentioning that this would solve it for addition, not saying this is the perfect way for life, the universe, and everything.

> Would it be that much slower, that it's an awful idea to do by default?

See, I'm not insisting on anything, I'm wondering and asking.

> Python gets away with it,

It doesn't do correct decimal addition either, so I'm not even focusing on resolving floating point inaccuracies, I'm more interested in "if it would be so slow to do arbitrary precision integers---oh and by the way, wouldn't it also solve this addition thing?"

Now, you also didn't exactly say that I was insisting, you said "someone who insists". So maybe this only applies to your parent comment. But every time I bring it up, people stumble over each other to tell me why it is this way. I already know why it is this way. There is a lot other words in the comment that one could reply to, and it's rather frustrating that it's completely overshadowed - every time - by people ignoring everything except those twelve magic characters: 0.1+0.2!=0.3.

[thaumasiotes]

>> a replacement for the + operator in javascript because computers can't do proper addition (0.1+0.2!=0.3).

> Just saying they can't do it (I edited this: first I said that JS doesn't do it properly, but I thought that was rather too narrow. I guess 'computers' is too broad again. Pick a name, you know what I mean)

You can say it, but that won't make it true. They can do it, and they do do it. Your comment is so much nonsense. The algorithm computers use to add 0.1 and 0.2 is the same algorithm that you use, which is, unsurprisingly, why they produce correct results.

> There is a lot other words in the comment that one could reply to, and it's rather frustrating that it's completely overshadowed - every time - by people ignoring everything except those twelve magic characters: 0.1+0.2!=0.3.

I'll point out again that I'm focusing on your completely unjustified claim that "computers can't do proper addition", which you didn't bother to include in "those twelve magic characters" that everyone is complaining about.

[mschuetz]

>> You can say it, but that won't make it true. They can do it, and they do do it. Your comment is so much nonsense. The algorithm computers use to add 0.1 and 0.2 is the same algorithm that you use, which is, unsurprisingly, why they produce correct results.

Are you aware of floating point math? That's what most languages, and almost all languages aimed at performance, use. It's defined in the IEEE 754 standard and supported on a hardware level in many devices.

Here is a listing of the result of 0.1 + 0.2 in various languages: https://0.30000000000000004.com/

As the URL already indicates, most languages, including C, Rust, C++, Java, Javascript, Clojure, FORTRAN, Python, etc. evaluate this to 0.30000000000000004. I'm fine with this, I need fast rather than precise math. But it's not "correct".