[boost] Re: Yet another Variant class

From: Itay Maman (itay_maman_at_[hidden])
Date: 2002-07-02 01:36:40

Joel de Guzman wrote:
> Itay Maman wrote
> 
>>
>> The Inheritance relationship is also a composition. 
> 
> 
> ? care to explain ? I always thought that inheritance (*is-a*)
> is different from aggregation (*has-a*).
> 
> Regards,
> --Joel
> 
> 
> 
When you define D to inherit from B, then, B becomes a semi-data member 
of D. The only difference is
that you need to use the "::" operator to access it (rather than the "." 
operator)
We can say that inheritacne is a compostion + some additional properties 
    (primarily: polymorphism). As explained by Sutter, These additional 
properties incur increased coupling which is a negative side-effect of 
inheritance.

struct B
{
    int x_;
} //

struct D1 : B
{
   void fff()
   {
       cout << B::x_;
   }
};

struct D2
{
   B b_;

   void fff()
   {
       cout << b_.x_;
   }
};