Yh, C++ (vc++) - rextester

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

#include <iostream>
#include <string>
#include <thread>
#include <chrono>

namespace detail_
{
    struct wait_for
    {
        explicit wait_for( unsigned int msecs ) : ms(msecs) {}
        const std::chrono::milliseconds ms ;

template< typename C, typename T >
        friend std::basic_ostream<C,T>& operator<< ( std::basic_ostream<C,T>& stm, wait_for w )
        { if(stm) std::this_thread::sleep_for(w.ms) ; return stm ; }
    };
}

template< typename C, typename T >
std::basic_ostream<C,T>& operator<< ( std::basic_ostream<C,T>& stm, std::pair< std::string, detail_::wait_for> str_slow )
{
    for( char c : str_slow.first ) stm << str_slow.second << c << std::flush ;
    return stm ;
}

std::pair< std::string, detail_::wait_for> slowly( std::string str, unsigned int ms = 250 ) 
{ return { str, detail_::wait_for(ms) } ; }

int main()
{
    std::cout << slowly( "hello world!\n" ) ; // with default delay of 250 ms between characters
}

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Compilation time: 1,77 sec, absolute running time: 3,7 sec, absolute service time: 5,48 sec