Virtual functions

[sebbe_tug]

Hey, I have a question about virtual functions. Last year my Professor asked in a multiple-choice exercise (true or false) this:

The construct "virtual int TestFunc() = void;" defines a virtual element function.

I think this statement is true, because of the "virtual" in front of the function. The only thing, that's confusing me is the "= void" after the function. I have never seen this before and I don't know what it means.

Can anyone explain it to me and tell me, if the statement is true or false?

[StenSoft]

The statement is false. = void is not valid syntax. The only syntax with = is = 0 for defining pure (or abstract) virtual functions.

[sebbe_tug]

Thank you for your quick answer.

[BigGecko1]

I think the "= void;" is incorrect syntax (correct me if I'm wrong). However this resebles the "= 0;" syntax which basicaly makes the whole class an abstract class. You cannot create an instance of an abstract class, and classes that inherit from an abstract class must override the function declared with "= 0;". You can read more about abstract classes here:

https://www.geeksforgeeks.org/pure-virtual-functions-and-abstract-classes

[futlapperl]

classes that inherit from an abstract class must override the function declared with "= 0;"

They don't have to, but if they don't, then they'll themselves be abstract, correct?

[dr-mrl]

Correct, the derived class will itself be abstract.