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From: Dennis Hoppe <dennis.hoppe@hoppinet.de>
Newsgroups: comp.lang.ada
Subject: Interface specification in Ada
Date: Wed, 11 Jun 2008 14:46:38 +0200
Organization: Aioe.org NNTP Server
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Date: 2008-06-11T14:46:38+02:00
List-Id: <comp.lang.ada>

Hi,

my preferred programming language is Java and I'm used to declare in an 
interface some common methods, that all subclasses have to implement. 
For example:

interface Bicycle {
   void changeCadence(int newValue);
   void changeGear(int newValue);
   void speedUp(int increment);
   void applyBrakes(int decrement);
}

class RacingBicycle implements Bicycle {
    // remainder of this class implemented as before
}

If I accidentially implement RacingBicycle without providing the four 
methods mentioned above, the compiler would draw attention to this 
situation.

In Ada, i found the keyword "interface" only in the context of multiple 
inheritance. The usage would be:

package Bicycle is
    type Object is interface;

    procedure changeCadence (newValue : in Integer) is abstract;
    procedure changeGear (newValue : in Integer) is abstract;
    procedure speedUp (increment : in Integer) is abstract;
    procedure applyBrakes (decrement : in Integer) is abstract;
end Bicycle;


with Bicycle;

package RacingBicycle is

    type Object is new Bicycle.Object with null record;

    -- omitted needed procedures to raise an error
end RacingBicycle;


Unfortunately, the build process runs through without any errors. In 
this case, I want the compiler to notify me about missing procedure 
implementations, because they are declared abstract in the interface.

I think, I missed something in the hierarchy, but I don't see it.


Thank you in advance,
   Dennis Hoppe