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

Subject: Re: [geometry] nsphere and views names
From: Barend Gehrels (barend_at_[hidden])
Date: 2013-06-23 11:11:48

Hi,

On 23-6-2013 0:20, Adam Wulkiewicz wrote:
> 2013/6/22 Bruno Lalande <bruno.lalande_at_[hidden] 
> <mailto: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?

What is the difference between view::as_centroid and the normal 
return_centroid? Same question for envelope. IMO all these calls are 
redundant - we have this already. What does as_bounds do?

Regards, Barend