Re: [boost] [review] pqs

From: David Greene (greened_at_[hidden])
Date: 2006-06-07 17:05:58

Andy Little wrote:

>>>The kilogram rather than the gramme  is a base unit in the SI. I think that 
>>>the
>>>history has to do with the emergence of the SI system from the C.G.S system.
>>>Presumably they decided that the gramme from the C.G.S system was too small a
>>>unit, the mystery then being why C.G.S used centimeters in the first place.
>>>Whatever. I agree the whole thing is a logicians nightmare. I'm just the
>>>messenger...
>>
>>But I don't understand why the SI "interface" commands a particular
>>pqs implementation.  From the user perspective, they don't really care.
>>But as soon as a programmer tries to extend the framework, nightmares
>>ensue.
> 
> 
> I dont think electrotechnology is an extension to the SI. IMO its a different 
> system in which bytes and time exists, but not mass, length, current etc etc.

We're not talking about Mibibytes here.  My question is, why does
someone extending the "mass" abstract quantity (is that the correct
term?) need to worry about prefix_offset?  Why isn't "kilo" specified
with "3" like it is everywhere else?

AFAICT this has no impact on the user interface.  The user will
just specify pqs::mass::kg and doesn't care what the underlying
"prefix number" is.  But this change makes the framework extender's
job much easier.

                             -Dave