Quantity.Equals(Quantity other, Quantity tolerance) gives false negative due to floating-point arithmetic

[AndreasLeeb]

Describe the bug The current implementation of e.g. Length.Equals(Length other, Length tolerance) can lead to false negatives at the boundaries of the tolerance (for instance when comparing a with a - tolerance).

To Reproduce

var tolerance = Length.FromMillimeters(0.5);
var length = Length.FromMeters(0.1);
Assert.True((length - tolerance).Equals(length, tolerance));

The assert fails, which makes sense if you rephrase it as Assert.True(((length - tolerance) - length).Abs() <= tolerance); which also fails as ((length - tolerance) - length).Abs().Millimeters == 0.50000000000000044 due to floating-point arithmetic.

Expected behavior That the above Assert with Equals returns true.

Additional context Tried it with UnitsNet 4.132.0, 5.43.0 and on the current master branch (1b3647fc1c32cbe737c07beca60ffa65c9c3d477).

[angularsen]

This seems similar to #1367 , let's discuss there for now.

[angularsen]

Closing this as by design for now, this is just how floating point works. Monitor #1377 for a possible fix on this using fractions.