Complexity Shock Horror II: the Sequel (was Re: MD5 in erlang .)

Chris Pressey cpressey@REDACTED
Tue Apr 8 01:09:09 CEST 2003

On Fri, 4 Apr 2003 16:08:37 +0200
"Robert Virding" <robert.virding@REDACTED> wrote:

> I see to remember from my physics days that an assistent professor
> once told of a system where all units were dimensionless and scalars.
> I can't remember its name though (it was many years ago!).

It's called "math class" :)

> As your message wasn't a 1/4 a small comment: there are so many
> measures that it would be practically impossible to do it.

I did do a fairly in-depth analysis of this once, and there are five
kinds of units that pose a problem (i.e. in the interests of producing
something usable, they'd probably be ignored), listed in the order of
increasing difficulty to implement:

1. variations on units (league -> statute? naut international? naut UK?)
2. tropical units (misnomers; 1 foot-pound =/= 1 foot * 1 pound)
3. units with a non-zero "zero point" (Celcius, Fahrenheit)
4. logarithmic units (deciBels, Richter scale)
5. subjective units (Beaufort scale)

Of course, there may also be others I missed.
But the exceptions do seem to be in the minority.  Most units behave
quite regularly.

> Also would
> conversions be automatic? I mean could you match metres with furlongs
> or seconds with fortnights and it would convert for you. I like
> furlongs/fortnight. :-)

I think they'd pretty much have to be automatic for it to be useful. 
But they could be specified explicitly as well.

Just imagine opening up a shell and typing

  14.9 parsec/jiffy in furlong/fortnight.


> Robert


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