Re: [boost] Preview 2 of a template Geometry Library

From: Arash Partow (arash_at_[hidden])
Date: 2008-03-28 09:04:35

John Femiani wrote:
 > This is why I would like to see concepts spelled out like this:
 > http://www.boost.org/libs/concept_check/reference.htm#basic-concepts
 > as is done by other boost libraries which I like, such as gil
 > http://stlab.adobe.com/gil/html/index.html,  BGL
 > http://www.boost.org/libs/graph/doc/graph_concepts.html , fusion, and
 > others.  They all clearly specify their concepts using the SGI style and
 > provide concept checking classes.  To me that makes them easy to
 > understand.
 >
 > IMHO the core need from a point library is the concepts, not the models,
 > because there are so many different well-tuned geometry libraries that
 > exist, and the idea is that boost _algorithms_ work on any "point",
 > rather than that boost have a great point class (those are easy).
 >

The questions here is should the concept(s) spell out each and every
property of the object (point for example)? In the on going example
of the distance routine, say I provide a point that is comprised of
my_rational type. but I have not defined a sqrt function for it, should
say stuff like that be definable as concept as well - if so where do we
stop?

 > Also, I already disagree about the idea that a point should have
 > coordinates.

I agree

 > CoordinatesConcept should be part of a separate concept. Of
 > course a useful point class will model both the coordinates and the
 > point concept. To me a point should really support transform, scale,
 > rotate, shear, and distance operations as free functions (maybe more).
 >
 > I don't know how to handle the idea of a 'space' or a 'kernel'.

Well they occur(are needed) when you want to re/define various operators
or truths. It would be go to somehow link type,object,routine and space
together - with obvious/common defaults provided by the library.

Arash Partow
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