Юля

class Audioformat {
public:  
	//Audioformat(){mp3_counter++;};
   virtual  string titel() { return ""; }
   virtual  string info()  { return ""; }
  virtual ~Audioformat() {};
   
   
};

int mp3_counter = 0;

class MP3_Format : public Audioformat {
public:
	
	MP3_Format(){mp3_counter++;};
	MP3_Format(MP3_Format &cop){
		MP3_Format(cop.song);
		mp3_counter++;
		}
	
	MP3_Format(const char* c_string) {
		 
        song = (const char*) c_string;
				mp3_counter++;

	}

   
    MP3_Format(string _song): song(_song){
		mp3_counter++;
		 }
		
		 	 
   MP3_Format& operator=(const MP3_Format&){
	   cout<< "Im here" ; 
	   return *this ; 
   }
   
   
		 ~MP3_Format(){mp3_counter--;}
    string titel()      { return  song; }
    string info()    { return "MP3"; }

	 operator string() const { return song; }
	 operator string() { return song; }
	     friend bool operator==(const MP3_Format& lhs, const MP3_Format& rhs)
    { 
        return lhs.song == rhs.song;
    }
    friend bool operator!=(const MP3_Format& lhs, const MP3_Format& rhs)
    {
        return !operator==(lhs,rhs);
    }
       MP3_Format& operator=(const char* c_string){
		   song = *c_string; 
		   return *this; 
	   }
	 
	  
		 
private:
    string song;
};

bool test_A1_e() {
#ifdef A1_e
	//MP3_Format mp3a("Summertime");
	MP3_Format mp3a = "Summertime";
	MP3_Format mp3b;
	mp3b = "Summertime";
	cout << mp3b.titel() << " mp3b.titel()"; 
	
	string ta = mp3a.titel();
	string tb = mp3b.titel();

	return (ta == "Summertime" &&
		tb == "Summertime" );
#else
	return false;
#endif
}

#include <iostream>
#include <thread>
#include <vector>
#include <cstdlib>
#include <algorithm>

#include <mutex>
using namespace std;
mutex m_sum;
void Work( double &sum ){ 	
    unsigned int n0 = 1;
    unsigned   int n1 = 1000001;
    double tmp; 
unique_lock<mutex> lck {m_sum}; 
 
	for (unsigned int j = n0 ; j<n1 ; j++) {
	tmp = 1.0/(j*j);
			double sum=sum+tmp; }
		cout << "b" ;	
	
	lck.unlock();}
	
bool sum(unsigned int number_threads)

{
    const double pi = 3.14159265358979323846264338327;
    const double exact = pi*pi/6.0;
    
       double s=0;

    thread* t = new thread[number_threads];
    
   for( long unsigned int i = 0; i < number_threads; ++i){
	  
 	t[i] = thread(Work, std::ref(s) );
	}
	
	  for( long unsigned int i = 0; i < number_threads; ++i){
 	t[i].join();
	}
 	delete []t;
 	cout << "sum=" << s;
    cout << "sum=" << s << " " << fabs(s-exact) << endl;
    
    return fabs(s-exact)<1e-4;
}