Iterable container as generic parameter

[Lionel Draghi <lionel.draghi@gmail.com>]

I would like to make a generic function containing this simple code :

for E of L loop
   Put_Line (Image (E));
end loop;

And I would like to have this generic compatible with all "iterable container".

I thought it would be possible by just providing as generic parameters the Image function, and an Ada.Iterator_Interfaces instantiation, but without referencing the container.
Isn't the iterator supposed to encapsulates both the cursor and the container?

Something like : 

generic
   type Cursor is (<>);
   with function Image (C : Cursor) return String;
   with package Iterator_Interfaces is 
     new Ada.Iterator_Interfaces (Cursor, others => <>); 
function List_Image return String;

But I couldn't figure out a simple way to do the body :
1. using the "for E of L" or the "for C in L.Iterate" loop refers to L, the Iterable container : why should I need that here? 

2. and it's not clear for me how to directly use a Cursor with First and Next functions provided by Iterator_Interfaces, that need a Forward_Iterator parameter.

Any hints?

Thanks,

-- 
-- Lionel