C++ 'mutable' keyword
- by Rob
A while ago I came across some code that marked a member variable of a class with the 'mutable' keyword.  As far as I can see it simply allows you to modify a variable in a 'const' method:
class Foo  
{  
private:  
    mutable bool done_;  
public:  
    void doSomething() const { ...; done_ = true; }  
};
Is this the only use of this keyword or is there more to it than meets the eye?  I have since used this technique in a class, marking a boost::mutex as mutable allowing const functions to lock it for thread-safety reasons, but, to be honest, it feels like a bit of a hack.