Geometry Boost List: Re: [geometry] nsphere and views names

Subject: Re: [geometry] nsphere and views names
From: Adam Wulkiewicz (adam.wulkiewicz_at_[hidden])
Date: 2013-06-22 18:20:47

2013/6/22 Bruno Lalande <bruno.lalande_at_[hidden]>

> Hi,
>
> I basically agree with the propositions discussed here. Regarding the
> pipe-style syntax - it's just an extra layer on top of the classic syntax
> we've already started (view_as / make_view_as etc...) so let's first
> finalize it and document it, then we can discuss more in detail what a
> higher level syntax would look like.
>
> My only concern is to produce unexpected and/or counterintuitive effects.
> "view_as<some geometry>" should always be an "exact" operation. That is, it
> should always return a geometry which is the exact equivalent of the input
> geometry (i.e. calling any algorithm on it should return the same result).
> For instance a 2D box can be exactly expressed in terms of a 2D polygon, a
> point can be exactly expressed in terms of a box (with null dimensions) so
> these are good uses. However, saying view_as<point>(sphere) and expecting
> it to return the center of the sphere is an abuse, the returned geometry is
> not geometrically equivalent to what we had in the first place. So that
> should be achieved by a more explicit call, for instance
> view_as_center<point>(sphere). I want to avoid obscure behaviors, basically.
>
>
I agree with this. So basically view_as<Geometry> would take
coordinate_type, tag, dimension, etc. from Geometry? But not necessarily
use/wrap/store/return the Geometry type?

I thought about using the same coordinate_type and dimension from the base
type.

Would you prefer to have those views in geometry:: namespace? What do you
think about geometry::view:: namespace? E.g.

view::as<Geometry>(other_geometry)
view::as_centroid<Point>(other_geometry)
view::as_min_corner<Point>(box_or_maybe_other_geometry)
view::as_max_corner<Point>(box_or_maybe_other_geometry)
view::as_envelope<Box>(other_geometry)
view::as_bounds<Box>(other_geometry)
view::as_bounds<NSphere>(other_geometry)

And btw, do you think that views could be used the way I presented - to
convert something into something else? Or just to access some data
unavailable because of the concept limitation? E.g. only to view Sphere as
it's center or box as it's min_corner?

Regards,
Adam