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by mcabbott
928 days ago
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using Unitful: m; foo(2.0m)
With the above definition, this will give DimensionError: 2.0 m and 1.0 are not dimensionally compatible.Probably this means you should define `foo(x::Number) = x + oneunit(x)` to respect the Number interface. But this interface isn't very strictly defined. I believe `Base.oneunit` was added after someone started writing the Unitful package -- building something useful in a legal grey area, and formalising later? |
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I don't know/use Unitful, but if that function didn't fail it's because the guys who wrote Unitful defined a promotion rule from Int to their Unit thingy. So.... that's how their type works. Don't use it. Or better, open an issue on github, they might have an explanation that's escaping us. I suspect it has to do with their mental model of what Unitful is supposed to achieve.
Let me tell you that my intuition agrees with you. As an ex-physicist, if I was designing a lib called Unitful I wouldn't let you sum sum 1 meter plus 1 unitless thing.
EDIT:
Actually, I just tried running your code and I do get DimensionError
I'm guessing you have some seriously outdated versions of something?EDIT2: Sorry I misread you. You do get an error. Ok I see your point. Maybe the Julia docs should more explicit about what the Number interface entails. Is `+ 1` allowed? You're assuming the answer is obvious, but it's not to me. In particular, that's not generic at all. You're probably right about `+ oneunit(T)`