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#include <iostream>
using namespace std;
 
class Coor
{
public:
    int x, y;
};
 
struct DataAccess
{
	virtual int Get(Coor &coor) = 0;
	virtual void Set(Coor &coor, int value) = 0;
};
 
struct AccessX : public DataAccess
{
	virtual int Get(Coor &coor) { return coor.x; }
	virtual void Set(Coor &coor, int value) { coor.x = value; }
};
 
struct AccessY : public DataAccess
{
	virtual int Get(Coor &coor) { return coor.y; }
	virtual void Set(Coor &coor, int value) { coor.y = value; }
};
 
bool algorithm(Coor &coor, DataAccess &accessor)
{
	cout << accessor.Get(coor) << endl;
	accessor.Set(coor, 100);
	cout << accessor.Get(coor) << endl;
	cout << "===============" << endl;
 
	return true;
}
 
int main()
{
	Coor coor;
	coor.x = 5;
	coor.y = 10;
 
	algorithm(coor, AccessX());
	algorithm(coor, AccessY());
}

prog.cpp: In function ‘int main()’:
prog.cpp:44: error: invalid initialization of non-const reference of type ‘DataAccess&’ from a temporary of type ‘AccessX’
prog.cpp:28: error: in passing argument 2 of ‘bool algorithm(Coor&, DataAccess&)’
prog.cpp:45: error: invalid initialization of non-const reference of type ‘DataAccess&’ from a temporary of type ‘AccessY’
prog.cpp:28: error: in passing argument 2 of ‘bool algorithm(Coor&, DataAccess&)’

Standard output is empty