Re: [office-formula] CONVERT - why not metric prefixes everywhere?

[Eike Rathke <erack@sun.com>]

Hi David,

On Tuesday, 2007-02-06 00:21:31 -0500, David A. Wheeler wrote:

> It's not clear why the prefixes should be limited to the metric units,

They don't have to, Excel just says so, and throws an error if they
aren't. Anyway, a kilomile _can_ be computed, how much sense it makes to
apply SI prefixes to imperial units or have a kiloCelsius or kiloknot,
well ... YMMV ;-)

We should add a portability constraint though that prefixes to other
than metric units may not be supported by applications.

> so I did a quick test to see if there's a problem if the prefixes are
> just accepted everywhere.  The attached program creates all possible
> combinations, and no conflict was found. There isn't even a problem if
> you also permit binary prefixes (Mi, etc.) everywhere, and support
> b (bit) and B (Byte) units.  You would only use those prefixes for
> information units, but even permitting them everywhere doesn't seem to
> be a problem.

Hmm.. "Pi" might conflict with "Pica", even if there is no unit "ca". So
far simply parsing away a prefix was a valid approach without these
binary prefixes.

> Is there some reason the metric prefixes shouldn't be just accepted everywhere?
> And should we also permit "b" (bit) and "Byte", along with binary prefixes for these two?

I don't see a strong reason why we should not permit it, with the
restriction of not being portable. Btw, OOo supports square and cubic
measures such as "km2" and "m3" and "acre" and "ha", and many more. Also
velocities like "m/s" and "km/h" and "kn" are supported. Do we want to
add them all?

> If we want to limit the prefix support, we need to clearly identify
> which units get the prefixes.  That gets tricky - how about seconds?
> Years? Celcius? Kelvin?

Wait a kilosecond while I cook the potatoes at 1000dC ... should be no
problem, though very unusual, and I would none of them (time and
temperature) consider metric.

> prefixes = [ "K", "E", "P", "T", "G", "M", "k", "h", "e", "d",
>             "c", "m", "u", "n", "p", "f", "a",

What's that with the upper case "K" there? Should be "Z" (Zetta)
instead, I think. Followed by "Y" (Yotta) == 10^24. Similar in the other
direction after "a" follow "z" (zepto) and "y" (yocto).

  Eike

-- 
Automatic string conversions considered dangerous. They are the GOTO statements
of spreadsheets.  --Robert Weir on the OpenDocument formula subcommittee's list.