Re: Interfaces in C++

From:
anon <anon@no.invalid>
Newsgroups:
comp.lang.c++
Date:
Fri, 10 Oct 2008 11:09:42 +0200
Message-ID:
<gcn611$esq$1@news01.versatel.de>
Pete Becker wrote:

On 2008-10-07 02:07:33 -0400, anon <anon@no.invalid> said:

Maik wrote:

On 6 Okt., 21:12, "A.Gallus" <u...@rz.uni-karlsruhe.de> wrote:

Bingo, that did the job, thx!

class A
{
   virtual void myfunc() = 0;
};

class B : public A
{


You should consider to prefer
  class B : public virtual A
to avoid being bitten by:
  
http://www.parashift.com/c++-faq-lite/multiple-inheritance.html#faq-25.8
which will most likely happen if one uses the interface pattern.


I think that is worse performance wise then just this:
class B : public A
At least thats what I read here:
http://www.agner.org/optimize/#optimize


And int is faster than double, so I won't use floating-point.
Unfortunately, that often gives the wrong answer.


What I suggested is "do not use it, unless you have to"

Seriously: virtual and non-virtual inheritance have rather different
meanings, and performance concerns (whether real or imaginary) never
overrule correct semantics.


http://en.wikipedia.org/wiki/Virtual_inheritance explains my
understanding of the virtual inheritance.

You haven't said what are differences in virtual and non-virtual
inheritance meanings.

Whether I am going to use a virtual inheritance depends on the design,
and I would not suggest to people to use it because it might prevent a bug.

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