bug#1018: 23.0.60; Calculator Units Table "weirdness"

[David Hansen]

On Wed, 24 Sep 2008 15:44:42 -0500 Jay Belanger wrote:

> David Hansen <david.hansen@gmx.net> writes:
> ...
>>> The values are stored that way, instead of as a float, when they are
>>> exact.
>>
>> What exactly is "exact"?
>
> "Exact" means exactly "exact". :)
>
>> Just to be a bit pedantic: the "meter" (and therefore every measure of
>> length/surface/volume) is *not* exact, it's an experimentally
>> determined quantity (the length that light travels 1/299792458
>> seconds).
>
> Right, so when the Calc units table says that c = 299792458 m/s, that is
> exact by definition.  Many units are defined in terms of other units,
> and then the values given in the units table are exact.  It's only
> conversions between two experimentally determined quantities (such as an
> astronomical unit and a meter) that are necessarily inexact.

I think I get it now.  But why is "Troy ounce" or "Horsepower" marked as
inexact?

The "year" looks weird too.  The only year that is 365.25d long is AFAIK
the "Julian Year" and this is *defined* to be that long.

> When the units table is displayed, having a conversion factor that is a
> float indicates that it isn't exact; if conversion factors like that
> between a tsp and ml are going to be displayed as a float, then there
> needs to be another indicator that some values are not exact.

That would be nice.  The unit table is incredible important to read
cooking recipes, now imagine you make a mistake by a whole order of
magnitude :)

David