A plehtora of Quantities

[Martin Hill]

We seem to be second/future-guessing a lot about units (lots of 'can we 
think of all possibilities'), which implies things are not as obvious as 
they may appear to be to some!  Let's leave it and see - we should be 
able to come back to BasicQuantity/etc later and modify it if required 
during this design phase.

David Berry wrote:
> Guy,
> 
> 
>>What if the real-world quantity is dimensionless? Should we add 'nodims' or
>>something as a kind of quasi-unit?
> 
> 
> Do you mean dimension-less, or unit-less? Angle is dimension-less, but it
> has units (rad.s, deg.s etc). Numbers which count something are
> dimension-less, but they can be said to have units of the thing they are
> counting. E.g. the FITS standard for units (see FITS-WCS paper 1) includes
> units like "pixel". Can you think of a quantity which has no units in this
> sense?
> 
> David
> 
> 
> 
> 
> 
>>On Thu, 13 May 2004, Alberto Micol wrote:
>>
>>
>>>>Want a quantity with errors but no units?  Go right ahead.
>>>
>>>
>>>I think we should forbid such option, really!
>>>Of course, unless you can convince me of the contrary.
>>>
>>>Alberto
>>>
>>>
>>>
>>
>>Guy Rixon 				        gtr at ast.cam.ac.uk
>>Institute of Astronomy   	                Tel: +44-1223-337542
>>Madingley Road, Cambridge, UK, CB3 0HA		Fax: +44-1223-337523
>>
> 
> 
> ----------------------------------------------------------------------
> Dr David S. Berry    (dsb at ast.man.ac.uk)
> 
> STARLINK project		 |	Centre for Astrophysics
> (http://www.starlink.ac.uk/)	 |	University of Central Lancashire
> Rutherford Appleton Laboratory	 |	PRESTON
> DIDCOT				 |	United Kingdom
> United Kingdom			 |	PR1 2HE
> OX11 0QX                                Tel. 01772 893733
>                                              01257 273192
> 


-- 
Martin Hill
www.mchill.net
07901 55 24 66