#include <iostream>
 #include <map>
 #include <shared_mutex>
 #include <string>
 #include <thread>

 std::map<std::string,int> teleBook{{"Dijkstra", 1972}, {"Scott", 1976},
  {"Ritchie", 1983}};

 std::shared_timed_mutex teleBookMutex;

 void addToTeleBook(const std::string& na, int tele){
   std::lock_guard<std::shared_timed_mutex> writerLock(teleBookMutex);
   std::cout << "\nSTARTING UPDATE " << na;
   std::this_thread::sleep_for(std::chrono::milliseconds(500));
   teleBook[na]= tele;
   std::cout << " ... ENDING UPDATE " << na << std::endl;
 }

 void printNumber(const std::string& na){
   std::shared_lock<std::shared_timed_mutex> readerLock(teleBookMutex);
   std::cout << na << ": " << teleBook[na];
 }

 int main(){

   std::cout << std::endl;

   std::thread reader1([]{ printNumber("Scott"); });
   std::thread reader2([]{ printNumber("Ritchie"); });
   std::thread w1([]{ addToTeleBook("Scott",1968); });
   std::thread reader3([]{ printNumber("Dijkstra"); });
   std::thread reader4([]{ printNumber("Scott"); });
   std::thread w2([]{ addToTeleBook("Bjarne",1965); });
   std::thread reader5([]{ printNumber("Scott"); });
   std::thread reader6([]{ printNumber("Ritchie"); });
   std::thread reader7([]{ printNumber("Scott"); });
   std::thread reader8([]{ printNumber("Bjarne"); });

   reader1.join();
   reader2.join();
   reader3.join();
   reader4.join();
   reader5.join();
   reader6.join();
   reader7.join();
   reader8.join();
   w1.join();
   w2.join();

   std::cout << std::endl;

   std::cout << "\nThe new telephone book" << std::endl;
   for (auto teleIt: teleBook){
     std::cout << teleIt.first << ": " << teleIt.second << std::endl;
   }

   std::cout << std::endl;

 }