Re: [boost] A design for geometric objects

Subject: Re: [boost] A design for geometric objects
From: Thomas Klimpel (Thomas.Klimpel_at_[hidden])
Date: 2008-11-14 13:00:09

> Wouldn't a typically C++-like approach be to use traits to ask each
> shape to present itself as an ellipse if it can?
>
> ellipse_traits<X>::get_length() and ellipse_traits<X>::get_width()
> would give the length and width that X has when viewed as an ellipse.
> ellipse_traits<ellipse> would simply define them as being its length
and width.
> ellipse_traits<circle> would define them as both being its radius.
> specialization ellipse_traits<rectangle> would not exist, meaning that
> a rectangle is-not-an ellipse.
> ellipse and circle would obviously be 2 completely separated classes.
>
> Do you think this approach is valid and could be generalized to all
> geometric shapes?

Now you have way to state "X can be viewed as an ellipse". But how would
you state "if X can be viewed as a circle, then it can be viewed as an
ellipse (in the way that ellipse_traits<X>::get_width() returns
circle_traits<X>::get_radius()"?