#include <iostream>
#include <future>
#include <chrono>
#include <condition_variable>
#include <iostream>
#include <mutex>
#include <string>
#include <thread>

using namespace std ;
int globalResult = -1 ;


void calculate_value()
{
    cout << "Calculating value in background...\n";
    this_thread::sleep_for( chrono::seconds(5) )  ; // Simulate long computation
    globalResult = 42 ;
}

int main()
{
    //Start the thread
	thread t1( calculate_value ) ;
	cout << "Main thread continues to execute...\n"  ;
	while ( globalResult == -1 )
	 {
		 //if ( globalResult != -1 )
		 //  cout << "Result: " << globalResult << endl ;
		 //else //wait some more
           this_thread::sleep_for( chrono::seconds(1) )  ;
	 }
     cout << "Result: " << globalResult << endl ;
     t1.join()  ;   // main thread waits for the thread t1 to finish
	/*
    future<int> future_result = async(launch::async, calculate_value);

    cout << "Main thread continues to execute...\n";

    cout << "Waiting for result...\n";
    int result = future_result.get(); // Blocks until the result is available

    cout << "Result is: " << result << endl;
     */


    return 0;
}