Hello,

Reading the April 95 WP I have not found the explicit answer for
two questions about abstract classes.
1) Is it possible to apply to the `sizeof' for the abstract class
   or a reference to abstract class ?
2) Is it possibale to apply unary `*' operator for the pointer to
   abstract class ? (Is it ok to use such application same way as
   unary `*' for incomplete type ?)

Thank you in advance,
--
Alexander N. Krotoff
Research Computer Center
Moscow State University


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In article <199609061452.RAA02042@such.srcc.msu.su>,
Steve Clamage <clamage@taumet.eng.sun.com> wrote:
>Hello,
>
>Reading the April 95 WP I have not found the explicit answer for
>two questions about abstract classes.
>1) Is it possible to apply to the `sizeof' for the abstract class
>   or a reference to abstract class ?

Yup and yup, although the latter is cause for debate.  (Not whether or not
you can do it..you can...but whether doing sizeof on a reference should
return the size of the underlying pointer, or the referred-to class.  This
debate has nothing to dowhether or not the class is abstract, BTW)





>2) Is it possibale to apply unary `*' operator for the pointer to
>   abstract class ? (Is it ok to use such application same way as
>   unary `*' for incomplete type ?)

No problem at all in dereferencing a pointer to an abstract base class.
It won't point to an instance of the ABC, but it will point to an instance
of a DERIVED class, and will access all of the derived class's methods,
instead of the base class's methods.

It's done all the time, and is one of the kay features of C++.


BTW; abstract classes are "complete".  You just cannot instantiate
one--that is the only difference.

Scott


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[Moderator's note: the quoted text wasn't actually written by Steve
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