Re: [boost] [geometry] area, length, centroid, behavior

Subject: Re: [boost] [geometry] area, length, centroid, behavior
From: Brandon Kohn (blkohn_at_[hidden])
Date: 2009-02-24 14:13:25

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From: "Sebastian Redl" <sebastian.redl_at_[hidden]>
> It's a matter of interpretation. If you consider a point a 0-dimensional
> object placed in the n-dimensional space you're working with, it doesn't
> have an extent over any number of dimensions. If, however, you consider
> it an n-dimensional object with an extent of 0 along every dimension, it
> does have length, area, volume, and whatever you want to call
> hyper-volumes in more than 3 dimensions, all of them being 0.
>

I agree that you can interpret these things as you have stated. The part 
that I find hard to accept is that I should somewhere in the code want:

point a;
line    b;
....
 //! Assuming the "dimensionally agnostic" function for the 'area' metric is 
called content.
double aArea = content( a );
double bArea = content( b );

My intuition tells me that such a call is far more likely to be a 
logic-error than the case that I really want to know the area of a point or 
line. So if I were defining the interface I would make the choice that I 
have advocated. Of course the world won't end if zero area is returned for 
points, lines (or type void for that matter.)

Brandon