[elcomet]

UnitInterval seems to contains an interval, not a single float. I don't think it's a very good name.

UnitIntervalNumber would be better, but it's too long. Something like UnitNumber or UnitFloat could maybe work.

[peterhil]

After reading this reply twice, I realised you are right and UnitInterval type indicates an interval object instead of a single scalar number.

I have actually used intervals, and should have realised this sooner. But I just had my first cup of coffee...

[dmurray]

Yes, UnitInterval is a really bad name for a single number. Astonishingly, it has 30 upvotes on SO.