[boost] Re: Quantity library: any interest?

From: Pavel Vozenilek (pavel_vozenilek_at_[hidden])
Date: 2003-04-13 10:42:42

Pavel Vozenilek wrote:
>> Quantity library is used to get safe conversions between different
physical
>> units

"Thorsten Ottosen" <nesotto_at_[hidden]> wrote in message
news:b7a22g$o6$1_at_main.gmane.org...
> I would say there is. But how do your work compare with SIunits?
>
http://www.fnal.gov/docs/working-groups/fpcltf/Pkg/SIunits/doc/0SIunits.html
>
> But how do your work compare with SIunits?
>
Wow.

I see few differences:

1. SIunits contains a lot of information related to physical units. It may
be scary to grok it for smaller app.

2. In SIunits 1 meter is always 1 meter. I used Quantity library in image
processing: here I have 1 centimeter in image space and 'different' 1
centimeter in screen space and conversion between them depends on current
zoom. I do not want blindly assign image length to screen length - that's
the main point of the library.

With SIunits I would need to create additional types to distinguish them.

3. With Quantity I may convert between different types: like image space
length (floats) and pixels (integers).

4. With Quantify the conversion may take into account changing runtime
parameters (e.g. zoom factor).

I think SIunits and Quantity are complementary: SUnits concentrates on
physics, Quantity helps to manipulate safely various application specific
units.

/Pavel