Compilare: user.cpp: In function ‘void build_convex_hull()’: user.cpp:95:40: warning: statement has no effect [-Wunused-value] debug && cout << stk.size() << "\n"; ^ user.cpp:97:93: warning: statement has no effect [-Wunused-value] debug && cout << a[stk[i]].x << " " << a[stk[i]].y << " " << a[stk[i]].slope << "\n"; ^ user.cpp: In function ‘void _backwards(std::set<Point, slope_compare>::iterator&)’: user.cpp:115:55: warning: statement has no effect [-Wunused-value] debug && cout << it->x << " " << it->y << "\n"; ^ user.cpp: In function ‘void update_hull(Point)’: user.cpp:146:147: warning: statement has no effect [-Wunused-value] debug && cout << position->x << " " << position->y << ", " << _next->x << " " << _next->y << ", " << __next->x << " " << __next->y << "\n"; ^ user.cpp:160:147: warning: statement has no effect [-Wunused-value] debug && cout << position->x << " " << position->y << ", " << _next->x << " " << _next->y << ", " << __next->x << " " << __next->y << "\n"; ^