Параметр шаблона ostream_iterator по умолчанию

#include <iostream>
#include <iterator>
#include <vector>
#include <algorithm>
#include <fstream>
 
template <typename T, typename OstIter = std::ostream_iterator<typename T::value_type, char>>
void copy_c(T& conteiner,
            typename OstIter::ostream_type &ost_t = std::cout,
            const typename OstIter::char_type *delim = " ",
            OstIter osit = std::ostream_iterator<typename T::value_type, char>(ost_t, delim))
{
   std::copy(conteiner.begin(), conteiner.end(), osit);
}
 
int main()
{
   std::vector<int> v {1,2,3,4,5,6,7};
 
   std::ofstream ofs("test.txt");
   copy_c(v);
   copy_c(v, ofs, ", ");
 
   return 0;
}

template <typename T, typename OstIter = std::ostream_iterator<typename T::value_type, char>>
void copy_c(const T& conteiner,
            OstIter osit = std::ostream_iterator<typename T::value_type, char>(std::cout, " "))
{
   std::copy(conteiner.begin(), conteiner.end(), osit);
}
 
int main()
{
   std::vector<int> v {1,2,3,4,5,6,7};
 
   std::ofstream ofs("test.txt");
   copy_c(v);
   copy_c(v, std::ostream_iterator<int>(ofs, ", "));
}

template <typename Cont, typename OutIter>
void copy_c(const Cont& conteiner, OutIter outIter)
{
   std::copy(conteiner.begin(), conteiner.end(), outiter);
}
 
template <typename Cont>
void print_c(const Cont& conteiner)
{
   std::copy(conteiner, std::ostream_iterator<typename Cont::value_type, char>(std::cout, " "));
}
 
int main()
{
   std::vector<int> v {1,2,3,4,5,6,7};
 
   std::ofstream ofs("test.txt");
   print_c(v);
   copy_c(v, std::ostream_iterator<int>(ofs, ", "));
}