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From: "Alex R. Mosteo" <devnull@mailinator.com>
Newsgroups: comp.lang.ada
Subject: Re: About 0Y interfaces
Date: Tue, 18 Oct 2005 16:34:08 +0200
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Date: 2005-10-18T16:34:08+02:00
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Dmitry A. Kazakov wrote:
> On Tue, 18 Oct 2005 14:49:04 +0200, Alex R. Mosteo wrote:
> 
> 
>>I hope someone can clarify some aspects of interfaces to me. I've read 
>>the description in several places but there are some things I'm not sure 
>>about.
>>
>>Firstly, interfaces are purely abstract, right? There's no way to 
>>provide a default/partial implementation except creating an object type 
>>which implements that interface.
>>
>>Secondly, we can create an object type which implements two or more 
>>interfaces. But I guess there's no multiple inheritance from classes, so 
>>you couldn't use two implementations of two different interfaces 
>>directly when creating a new type. Is this right? You'd need to use, for 
>>example, member objects and use proxy calls.
> 
> 
> I think the answer depends on what is meant under "implementation":

I was refering to implementation of the primitive operations.

> 1. Implementation of the values
> (data implementation)

I'm not sure what this means. I'd say that you're not refering to data 
initialization, since one can't provide record definition for an interface?

> 2. Implementation of the primitive operations
> (type interface implementation)

This is what I had in mind. Let's say for example that you want a 
primitive operation to always make a dispatching call on another 
operation. You can't model this in the interface, right?

> 3. Implementation of class-wide operations
> (class interface implementation)

I don't see any issue here. Just provide the subprograms you consider 
necessary taking classwide objects?