Comments (6)
The slight difference in the values is a side effect of normalizing the internal value in meters and floating point imprecision. While PartialEq
is implemented, I don't believe it will help in this case.
Floating point accuracy problems are always a hassle! You can see how uom
's test code uses approx here:
Lines 110 to 140 in 629f385
from uom.
Oh, whoops. I was the assert_relative_eq
macro. The error was about not implementing the crate's RelativeEq
trait.
from uom.
Are you proposing implementing approx::RelativeEq
inside uom
? If we're going to expose approx
in uom
's public interface I'd want to review other options. In a very brief scan I also found float-cmp
and assert_approx_eq
. All three seem pretty popular. I'm hesitant to pick a winner, but the orphan rules sort of require doing that.
from uom.
I'm hesitant to pick a winner, but the orphan rules sort of require doing that.
Could you expand on why that is the case? Couldn't uom
theoretically implement the traits from all three crates (and in different versions if required)? Also even if uom
provides an implementation of only one trait, can't downstream crates still implement the other using newtype wrappers just like they have to do now for any of them? (Which would even allow overriding a provided implementation with the same effort as implementing it in the first place now.)
from uom.
I hadn't thought about the opposite and adding multiple implementations. Similar question though, when should the line be drawn on which external crates should be implemented?
from uom.
Similar question though, when should the line be drawn on which external crates should be implemented?
Where you as the maintainer want it to be drawn from an effort versus convenience perspective. Since the basic set of implementable traits is unaffected, the stakes for answering this are not that high, i.e. you can choose one that you like to provide a convenient path for some users while not blocking anything for others.
Of course, just saying no is also a maintainer's prerogative and providing none also does not block anyone from using newtype wrappers. My point basically is that the orphan rules only enforce one thing here: This crate is the only place where we can provide these trait implementations without the additional effort of newtype wrappers.
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Related Issues (20)
- Unable to `clamp` quantity to a range. HOT 2
- Allow subtracting two thermodynamic temperatures HOT 3
- Deserialize references to quantities HOT 2
- New unit `ElectricalSusceptance` HOT 1
- Change of base_unit of Ratio quantity HOT 1
- Conversion to/from complex storage types is wrong
- Quantity-Aware access parts of quantity with complex storage type HOT 2
- Consider rust-specific cache action HOT 1
- Built-In SI system has no alias for Angular Momentum
- Unit conversion problem using BigRational
- Unclear about how to create arbitrary quantities with arbitrary units HOT 6
- Conversion to Watts HOT 1
- Newbie Feedback HOT 1
- New release HOT 1
- NIST Special Publication link
- Add a feature for bytemuck and/or zerocopy to `Quantity`
- Support fixed-point storage type(s)
- Better precision and abbreviation change for `astronomical_unit` HOT 6
- Implement clamp for f64 Quantities
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