how to boost::range_size work?

I want to write code like this:

#include <vector>
#include <iostream>

#include <iterator>

template<std::size_t N>

std::vector<int> to_vector(const int i[N]){

    std::vector<int> v;

    v.assign(i,i+N);

    return v;

};

int main(){

    int V[5]={1,2,3,4,5};

    std::vector<int> vec=to_vector(V);

std::copy(vec.begin(),vec.end(),std::ostream_iterator<int>(std::cout,"
"));
    std::cout<<std::endl;

    return 0;

};

but compillers does not calc parameter for 'to_vector' template
automatically so I have to write
std::vector<int> vec=to_vector<5>(V);

obviously it is not convenient issue because declaration of V can be
very far from this code...
and sizeof(V)/sizeof(int) is to long...
and preprocessor's macros is not c++ style.

But there is 'range_size' in boost library which do such thing but in
unknown way :-) does somebody know how it work? :-)

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