TITLE: Private virtual methods


PROBLEM: bs@alice.att.com (Bjarne Stroustrup)

Virtual private functions ought to exist for reasons of orthogonality
alone. However, there is also a	real use for them. To quote the ARM (pg256):

	Private virtual functions provide a way for the
	implementation of a base class to rely on derived
	classes without the functions involved being exposed
	to the general users of the base class. Whether the
	derived class chooses to expose the functions to its
	users is not a concern for the base class writer.
 
This comes in handy for classes that provides some fairly general
and standard services to users and implementations are completed
by functions supplied by derived classes.


RESPONSE: sdm@cs.brown.edu (Scott Meyers), 16 Mar 93


I don't much care for this argument, because it results in software designs
whereby derived classes are supposed to override functions they can't call.
Conceptually, these are "write-only" functions, and that makes no sense to
me.  I believe that all virtual functions should be either protected or
public, but I'd be interested in hearing arguments to the contrary.