print_tuple.cpp

/* 
 * FILE:        print_tuple.cpp
 * DESCRIPTION: Print the contents of a std::tuple<>.
 * DATE:        06/25/2020
 */
#include <iostream>
#include <tuple>

template <int I=0, typename ...T>
void print_tuple(
  std::ostream& stream,
  std::tuple<T...>& tup)
{
  const size_t tup_size=sizeof...(T);
  if constexpr (I<tup_size) {
    stream << std::get<I>(tup);
    print_tuple<I+1>(stream, tup);
  }
}

int main() {
  auto my_tuple=std::make_tuple(0,0,0);
  print_tuple(std::cout, my_tuple);
  return 0;
}

Another way to generate the calls to std::get which avoids recursion is shown below.

template <typename T, size_t ...Is>
static void print_tuple_impl(
  T&& tuple,
  std::index_sequence<Is...>)
{
  ((std::cout << std::get<Is>(tuple) << ' '), ...); // C++17 fold expression using operator `,`.
} 

template <typename ...T>
void print_tuple(std::tuple<T...>& tuple) {
  print_tuple_impl(tuple, std::make_index_sequence<sizeof...(T)>{});
}

This avoids the overhead of generating the recursive template function, which grows in proportion to the size of the tuple being printed.