Anthony Williams wrote in a message:
> 
> I've just had a thought about how to implement the strong guarantee for
variant, at the expense of larger space requirements --- have *two* copies
of > the internals, with a flag to indicate which is valid. Then, when
swapping or assigning, copy construct the value from the other variant into
the unused > space, and destruct the original and switch the flag when
everything is done.
> 
> What do people think?
> 
> Anthony
> 


I don't think it is possible - in the general case - to create two identical
instances of a class.
Consider this class:

// Just another class
struct jac
{
    jac* inst_p_;
    int n_;

   jac(int n = 0)  : n_(n)
   {
     inst_p_ = this;
   }

   jac(const jac& other) : n_(other.n_)


      inst_p_ = this;
   }

   jac* get() { return inst_p_; }
   void set(jac* inst_p) { inst_p_ = inst_p; }
} ;




--
Itay Maman
    itay_maman@[...].com
    maman@[...].com

This message expresses my personal opinion.




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