mutable keyword in C++
This keyword is only used in C++. The mutable keyword can be used for class member variables. Mutable variables are allowed to change from within const member functions of the class. ``` #include <iostream> using namespace std; class A { public: mutable int v; void change (int i) const { v = i; } }; int main() { A a; a.change(1); cout << a.v << endl; } ```