Geometry Boost List: Re: [geometry] Using iterator_range as a Geometry

Subject: Re: [geometry] Using iterator_range as a Geometry
From: feverzsj (feverzsj_at_[hidden])
Date: 2012-05-25 10:01:35

hi, Sakari 

Sakari Bergen wrote
> 
> Hello,
> 
> First of all I'd like to note that I am fairly new to both Boost.Geometry
> and Boost.Range, so I might be doing something non-optimal here.
> 
> I'm using two boost::circular_buffers to store "events" (time stamps and
> points), one containing the time stamps and the other the points. I need
> to
> make linestrings out of a subset of the points, and currently I'm using
> iterator_range to achieve this in an efficient manner. However, the
> problem
> I'm facing (which I did solve, a code snippet will follow) is that the
> linestring template assumes that all containers take two template
> parameters, the type and the allocator, where as iterator_range uses the
> iterator type as it's only template parameter.
> 
> I solved the issue by making an adapter class template, which takes the
> correct template parameters (the second one being unused), and provides
> the
> appropriate two iterator constructor so that it can be used with
> linestring. I wrapped all of this in macros and typedefs to make it more
> generic and easier to use.
> 
> I was wondering if there is an easier way to do this, or if the library
> could be modified in some way to make it easier?
> 
> -Sakari-
> 
> Here's the code:
> 
> -----------------------
> 
> // Iterator range adapter for boost::geometry stuff
> // (which expects containers to have two template parameters: T and
> Allocator)
> #define ITERATOR_RANGE_ADAPTER(ClassName, ContainerType, IteratorType) \
> template<typename T, typename Unused> \
> class ClassName \
>         : public boost::iterator_range<typename
> ContainerType<T>::IteratorType> \
> { \
>         typedef typename ContainerType<T>::IteratorType iterator_; \
>         typedef boost::iterator_range<iterator_> base_class_; \
> public: \
>         ClassName(iterator_ b, iterator_ e) : base_class_(b, e) {} \
> };
> 
> // Uses the above to adapt a iterator range to a line string
> #define ITERATOR_RANGE_GEOMETRY_TYPEDEF(TypedefName, GeometryType,
> PointType, ContainerType, IteratorType) \
> ITERATOR_RANGE_ADAPTER(TypedefName##Adapter, ContainerType, IteratorType)
> \
> typedef GeometryType&lt;PointType, TypedefName##Adapter&gt; TypedefName;
> 
> -----------------------
> 
> After which I can do (Point3D is a typedef for a geometry::point):
> 
> ITERATOR_RANGE_GEOMETRY_TYPEDEF(RangeLinestring,
> boost::geometry::model::linestring, Point3D, boost::circular_buffer,
> const_iterator)
> RangeLinestring rls(some_cb_iterator, other_cb_iterator);
> 
> _______________________________________________
> Geometry mailing list
> Geometry_at_.boost
> http://lists.boost.org/mailman/listinfo.cgi/geometry
> 

a dirty and quick way, just as a hint

// this will register any iterator_range<> as ggl linestring

namespace boost{ namespace geometry{ namespace traits{

template<class Iter>
struct tag<iterator_range&lt;Iter> >
{
    typedef linestring_tag type;
};

}}}

regards, zsj

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