#include <iostream>
using namespace std;

class base{
private:
   double d;
public:
	double pub;
	base():d(1.7){}
	void setD(double pd){d = pd;}
	double getD()const{return d;}
	friend ostream& operator<<(ostream o, base b);
};
ostream& operator<<(ostream &o, base b){
		o << b.getD();
		return o;
}

// default inheritance is private
class child1:base{
public:
	// how to call the base class constructor
	child1():base(){}
	// not allowed to access d from base 
	//void setD(double pd){d = pd;}
	// allowed to access public variables from base
	void setPub(double ppub){pub = ppub;}
};

// public can access all public
class child2: public base{
public:
	child2():base(){}
};

// can access all public data
class child3: protected base{
public:
	child3():base(){}
};

// can access all public data
class child4: protected base {
public:
	child4():base(){}
	// child4 can access getD, but main can not
	double goGetD(){return getD();}
};

void main(){
   base b;
   cout << b << endl;
   b.setD(3.14159);
   cout << b << endl;
   child1 c1;
   // does not work, default inheritance is private
   //cout << c1.getD() << endl; 
   child2 c2;
   cout << c2.getD() << endl;
   child3 c3;
   // does not work, because of protected keyword
   //cout << c3.getD() << endl;
   child4 c4;
   // does not work, because of protected keyword
   cout << c4.goGetD() << endl;
}