To interface or not to interface

[Steven Schveighoffer]

On Tue, 25 May 2010 23:29:34 -0400, Walter Bright  
<newshound1 at digitalmars.com> wrote:

> Steven Schveighoffer wrote:
>> On Mon, 24 May 2010 18:13:38 -0400, Walter Bright  
>> <newshound1 at digitalmars.com> wrote:
>>
>>> Steven Schveighoffer wrote:
>>>> All an interface does is give an abstract representation of functions  
>>>> that are *already there*.  Removing the interface does not remove the  
>>>> functions that implemented the interface.
>>>
>>> Then why do interfaces need to be part of the collection component?  
>>> Why can't the user add them if he wants them?
>>  How do you add an interface to a class?
>
> Define an interface who's member functions call the class' member  
> functions.

Quoting from earlier message:

   Wrapping seems like it would add more overhead than just implementing  
the interface, especially since D's inliner has some strange restrictions.

-Steve