
Geometry : 
Subject: Re: [geometry] nsphere and views names
From: Barend Gehrels (barend_at_[hidden])
Date: 20130623 11:11:48
Hi,
On 2362013 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 pipestyle 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
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