Gerhard Wesp Sent:
On Thu, May 25, 2006 at 04:41:32PM +0200, Maarten Kronenburg wrote:
Users can implement an unsigned_integer by deriving from integer, but this will not give any performance gain.
This would violate Item 32 in Effective C++, 3rd ed. by Scott Meyers: Make sure public inheritance models "is-a".
I agree it's not a good idea.
I suggest deriving from integer be disallowed in the TR2 proposal.
... however I don't think that is. If C++ had "final", then it could be compile time checked. As it is, I don't think TR2 could do more than make it undefined behaviour. We really don't want more undefined behaviour in C++ if we can avoid it. What is more, deriving from integer would actually work on all implementations (as far as public inheritance which doesn't model "is-a" works). -- Martin Bonner Martin.Bonner@Pitechnology.com Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB4 6WZ, ENGLAND Tel: +44 (0)1223 203894