typename outside templates, C++ (vc++)

Language: Layout:

//Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23506 for x86

#include <iostream>
#include <chrono>
#include <type_traits>
#include <thread>
#include <ctime>

namespace time_utils
{
    using clock_type = typename std::conditional< std::chrono::high_resolution_clock::is_steady,
                                                  std::chrono::high_resolution_clock,
                                                  std::chrono::steady_clock >::type ;
                                                  
    // after every 'interval_millisecs' milliseconds, call function 'fn'; repeat 'count' times
    template< typename FN > void periodic_repeat( FN fn, unsigned int interval_millisecs, unsigned int count )
    {
        for( unsigned int i = 0 ; i < count ; ++i )
        {
            std::this_thread::sleep_for( std::chrono::milliseconds(interval_millisecs) ) ;
            fn() ;
        }
    }

struct curr_time {} current_time ;
    std::ostream& operator<< ( std::ostream& stm, curr_time )
    {
        const auto now = std::time(nullptr) ;
        return stm << std::ctime( std::addressof(now) ) ;
    }
}

int main()
{
    std::cout << "program start: " << time_utils::current_time ;
    
    const auto start = time_utils::clock_type::now() ;
    time_utils::periodic_repeat( [] { std::cout << " current time: " << time_utils::current_time ; }, 2000, 4 ) ;
    const auto end = time_utils::clock_type::now() ;

std::cout << "elapsed: " << std::chrono::duration_cast<std::chrono::seconds>(end-start).count() << " seconds.\n" ;
}

Show compiler warnings [ + ] Compiler args [ + ] Show input
Compilation time: 1,86 sec, absolute running time: 8,31 sec, absolute service time: 10,19 sec