RE: [sv-ec] email ballot: response Mantis 2698

id 57, svdb 2698    _____ YES   __X__ No

http://www.eda.org/svdb/view.php?id=2698 

[Alsop, Thomas R] I am not convinced that 'pure' is required in order to
create what is coined a "pure virtual method'.  It's really ambiguous
and seems like you can create a prototype virtual method and any level
of abstract class hierarchy and only be forced to override it when you
extend it to a non-abstract class and hence create the object out of it.
I guess I am asking what the intent behind the 'pure' keyword is?  If an
abstract class at any level only prototypes a method, does that mean we
have to label it 'pure'.  

 

[DR] No. an abstract class does not need to contain pure virtual
methods, but a pure virtual method can only be contained in an abstract
class.

 The "pure" keyword does two things:  It says what follows is a
prototype with no implementation, just like what "extern" does.
However, the extern keyword requires that you provide an implementation
(a body) that becomes part of the class definition, regardless of
whether  the method is virtual or not, or whether the class is abstract
or not. 

The other thing the pure keyword does is say that  I'm not providing an
implementation in this abstract class, creating a requirement that
someone provide an implementation in the form of an override in an
extended class before you can construct a non-abstract class object. 

 

Dave

 


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