Re: [Boost-users] can not compile nearest neighbors in d dimensions

Subject: Re: [Boost-users] can not compile nearest neighbors in d dimensions
From: Adam Wulkiewicz (adam.wulkiewicz_at_[hidden])
Date: 2014-04-16 14:27:24

Georgios Samaras wrote:
> I increased and it compile. However, I am -again- not able to 
> continue, because now it says point not declared..
>

If you're talking about the point identifier used in the main() function 
then yes, the compiler is right. The point type is declared inside 
do_something() and is visible only inside this function. I understand 
that template metaprogramming may be confusing but typedefs and 
functions are elements of C language. I advice you to learn more about 
C++ before proceeding. C++ Primer Plus by Stephen Prata is a nice book 
but I'm sure you can find more in the Web.

This mailing list doesn't cover general C++, only Boost-related 
questions should be posted here.

Regards,
Adam

> #include <boost/geometry.hpp>
> #include <boost/geometry/geometries/point.hpp>
> #include <boost/geometry/index/rtree.hpp>
>
> namespace bg = boost::geometry;
> namespace bgi = boost::geometry::index;
>
> template <int CompileTimeDimension>
> void do_something()
> {
>     typedef bg::model::point<float, CompileTimeDimension, 
> bg::cs::cartesian> point;
>     bgi::rtree<point, bgi::linear<8> > rt;
> }
>
> template <std::size_t D, std::size_t N>
> struct fill
> {
>     template <typename Point>
>     static void apply(Point& p, typename 
> bg::coordinate_type<Point>::type const& v)
>     {
>         bg::set<D>(p, v);
>         fill<D + 1, N>::apply(p, v);
>     }
> };
> template <std::size_t N>
> struct fill<N, N>
> {
>     template <typename Point>
>     static void apply(Point&, typename 
> bg::coordinate_type<Point>::type const&) {}
> };
>
>
> int main()
> {
>     int M;
>     M = 100;
>     if ( M == 100 )
>         do_something<100>();
>         else if ( M == 10000 )
>         do_something<10000>();
>         else
>         std::cerr << "invalid dimension!";
>     point p;
>     if ( M == 100 )
>         fill<0, 100>::apply(p, 5);
>         else if ( M == 10000 )
>         fill<0, 10000>::apply(p, 5);
>         else
>         std::cerr << "invalid dimension!";
>     return 0;
> }