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Comment by knocte | Hacker News Reader

Why not just use C# instead of staying in the shitty alternative? You know... https://twitter.com/knocte/status/1207544365607985152

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Both these expressions return the same result in both C# and JavaScript:

0.1 + 0.1 == 0.2; //= true

0.1 + 0.2 == 0.3; //= false

It's not the language, it's https://floating-point-gui.de

I was going to reply that I thought the point of the video/tweet is that JS does choose floating point by default while others don't. But I stand corrected, C# default sucks too: it uses the double type!

And here I thought that by using F# I would even be protected from this shit but unfortunately it has the same problem... Performance should be opt-in! (favouring correctness over it) :facepalm:

Thanks

First you should state the correctness level you need. 0.2? 1/7? sqrt(2)+pi? int n=0, n<inf, sum(1/n^3)?

Look at the decimal type; it's less performant, but you'll avoid floating point issues.

https://docs.microsoft.com/en-us/dotnet/api/system.decimal?v...

Yes I know the decimal type and it's what I use in all my code, I just thought the default would be something with more precision than double/float even if not decimal.

decimal is still floating-point, just decimal floating-point instead of binary. Things like 1/3 can still not be represented exactly. It's just that for values given in base 10 there's no transformation of the representation and 0.3 remains exactly 0.3.

I'm not sure you appreciate how much performance would be lost...

This video has nothing to do with Javascript. It's the correct implementation of floating point arithmetic, and would behave the same in any language. If you want 0.1 + 0.2 == 0.3, you should use decimal, not floating point - regardless of the language.

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