Object oriented programming and interfaces

[Dirk]

The distance function is implementation dependend and can only be 
computed between two objects of the same class (in this example 
the class is Item).

My goal is to write a module for a k-medoids clustering 
algorithm. The class MedoidClassification shall be able to 
partition a list of objects from the same class, which implement 
the Medoid interface.

My current approach is this (which does not work):

interface Medoid {
     float distance( Medoid other );
     uint id() const @property;
}

class Item : Medoid {
     float distance( Item m ) {...}
     uint id() const @property {...}
}

class MedoidClassification {
     this( Medoid[] list ) {...}
     Medoid[][] getClusters() {...}
}

void main() {
     Item[10] items;
     auto mc = MedoidClassification( items );
}


What would be a good way to implement this?