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Subject: Re: [geometry] Run-Time specified geometries
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2013-10-23 11:28:52

On 23 October 2013 08:58, Samuel Debionne
<samuel.debionne_at_[hidden]> wrote:
> Hello all,
> I'm wondering if someone is working on a runtime layer above the actual
> Boost.Geometry. Something in the same vein than GIL's dynamic images
> (any_views and algorithms that accept and dispatch such runtime/variant
> types).
> I have done a few experiments with Boost.Variant but before going on I
> would like to make sure that it's not already a work in progress.

As mentioned in this thread about WKB
variant or dynamic geometry type has been discussed some time ago.

We started the discussion based on some prototype for "any_geometry" I
made here:

Eventually, we agreed to use boost::variant and Bruno proposed it here:

In fact, variant geometry type in action is also presented in examples
for the spatial index:

So, this is work in progress, indeed.

> If we call dynamic algorithms, an overload that take dynamic geometries
> as inputs, the main difficulty I have encountered with dynamic
> algorithms is that there are instantiated with every possible type the
> variant can take. Some kind of filtering (e.g. types should have same
> dimensions) using traits and tag dispatching must be in place within the
> variant visitor. The other difficulty is with the return type that may
> depends on the input types, but no meta function (think result_of) is
> available.

Yes, so all possible instances need to be available.

> I found out that Bruno submitted some prototype. Is there a place
> (Wiki?) where we could write / discuss about it ?

There is Boost Wiki which I believe could be used for such discussion,
but AFAIK it requires a request for account.

IMHO, this can be discussed here on the mailing list.

Best regards,

Mateusz  Loskot,

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