Re: [boost] Infinite precision integer draft

From: Maarten Kronenburg (M.Kronenburg_at_[hidden])
Date: 2006-05-26 07:58:17

Bronek,
Thanks for your comments.
With respect to inheritance I take the
opposite view:
Inheritance is something that is part of C++
and therefore users are always allowed to
derive from any class.
There is no way of explaining to a user that
for some technical reason (like the destructor
is not virtual), it is not allowed to derive from
a class.
And as mentioned in my reply to Gerhard,
every unsigned integer is an integer, so there
is every reason to choose this design.
Regards, Maarten.

"Bronek Kozicki" <brok_at_[hidden]> wrote in message
news:000d01c680b8$3b311cd0$4904a8c0_at_actix.com...
> Bronek Kozicki <brok_at_[hidden]> wrote:
> > Gerhard Wesp <gwesp_at_[hidden]> wrote:
> >> This would violate Item 32 in Effective C++, 3rd ed. by Scott Meyers:
> >> Make sure public inheritance models "is-a".  I suggest deriving from
> >> integer be disallowed in the TR2 proposal.
> >
> > I second that. If the class has not been designed from the ground up
> > (virtual functions, interface classes etc.) to allow sensible
> > inheritance, it should be disallowed.
>                             ^^^^^^^^^^
>
> oops, I used too strong word here. I only hope than next sentence ...
>
> > I think that all STL classes
> > follow that rule.
>
> ... might explain what I actually meant. But let mi clarify: if class
> does not make proper use of inheritance, it should not mislead its user
> that it been designed to do so. Virtual destructor is kind of
> declaration "this class is designed to be inherited from", but it does
> NOT make it "good OOP-player". It the property of the design that can be
> recognized by use of interfaces and virtual functions and not virtual
> destructor alone. If integer type does not employ this kind of design,
> it should not mislead its users by providing virtual destructor. Making
> destructor public and nonvirtual does not make inheritance "illegal", it
> just declares that class had not been designed to be used as a base
> class. And this is how in my opinion integer class is designed and I
> like this design. Virtual destructor would only add confusion - because
> it would raise questions about contract between base class and its
> children  (there is no contract in the project, thus inheritance does
> not make sense).
>
>
> B.
>
>
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