Re: Can copy assignment operator be const?

class Base; // class hierarchy of dynamically created objects.

struct PVoid {
    PVoid(): p_(0) {}
    PVoid(const Base* p);
    PVoid(const PVoid& b);
    ~PVoid();
    const PVoid& operator=(const Base* p) const;
    const PVoid& operator=(const PVoid& b) const;
    const Base* operator->() const { return p_; }
    Base* operator->() { return p_; }
    const Base& operator*() const { return *p_;}
    Base& operator*() { return *p_;}
private:
    mutable Base* p_;
};

In the end, I have something like following (simplified, in real code
only derived classes are used both for pointers and entity objects).

PVoid a = new Base();
a->f(); // calls non-const f
const PVoid b;
b = a; // would not work without const assignment.
b->f(); // calls const f

This corresponds to:

Base* a = new Base();
a->f(); // calls non-const f
const Base* b;
b = a;
a->f(); // calls const f

So I prefer to think that the smartpointer class is designed this way
in order to keep semantics *unchanged* for this similar syntax. Yes I
know this is not really the case ;-)