Private visible?
Dave
Dave_member at pathlink.com
Thu Jul 13 12:23:34 PDT 2006
Walter Bright wrote:
> Dave wrote:
>> Everyone seems to agree that 'private' should not be accessible and
>> the current behavior is a bug. What we're all wondering is if
>> 'private' can also mean 'invisible' because that seems to be more
>> intuitive. Than you don't have that extra level of complexity for
>> lookup resolution and things like error messages describing a private
>> interface.
>
> The original reason why private members would be visible but not
> accessible has been forgotten. However, there were some significant
> issues brought up with making them invisible:
>
> 1) function overloading - if various overloads of a function have
> different protections, different functions will be selected even though
> the same arguments are presented. This can be surprising when code is
> moved around. If they are visible, you'll get an error message instead
> of silently varying behavior.
>
> 2) function overloading - one could lose the ability to 'poison' an
> operation on certain argument types, because instead the private
> function will not be seen and another selected.
>
> 3) function overriding - if a private function in a derived class
> overrides a public one in a base class, this overriding will not happen
> if the private function is invisible. Not only does this break
> encapsulation, it prevents the design pattern of being able to 'poison'
> certain operations on a class.
I don't wish to belabor this, but it would seem that the above great
reasons for "visible but not accessible" conflict with the current
behavior described here:
http://www.digitalmars.com/drn-bin/wwwnews?digitalmars.D.bugs/7649
So there are probably some bugs in there, especially with regard to #3
above and #2 in Kris' post. This to me is a before 1.0 thing.
Thanks,
- Dave
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