Re: how to prefer one template function over the other

#include <iterator>
#include <type_traits>
#include <vector>
#include <iostream>
#include <set>
#include <list>

template<class Cont>
struct has_back_insertion
{
    template <class U>
    static double test(...);

    template<class U>
    static char test(decltype(U().push_back(decltype(typename std::iterator_traits<decltype(U().begin())>::value_type())()))* ptr);

    enum
    {
        value = sizeof(test<Cont>(nullptr)) == sizeof(char)
    };
};

int main()
{
    bool hasback1 = has_back_insertion<std::vector<int>>::value;
    std::cout << "std::vector<int> has back insertion (push_back) support - " << (hasback1 ? "true" : "false")<< std::endl;

    bool hasback2 = has_back_insertion<std::set<int>>::value;
    std::cout << "std::set<int> has back insertion (push_back) support - " << (hasback2 ? "true" : "false")<< std::endl;

    bool hasback3 = has_back_insertion<std::list<int>>::value;
    std::cout << "std::list<int> has back insertion (push_back) support - " << (hasback3 ? "true" : "false")<< std::endl;

    bool hasback4 = has_back_insertion<double>::value;
    std::cout << "double has back insertion (push_back) support - " << (hasback4 ? "true" : "false")<< std::endl;

    std::cin.ignore();
    return 0;
}

Works fine with GCC 4.6, busted on VS 2010 SP1

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