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From: Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>
Newsgroups: comp.lang.ada
Subject: Re: Specialization
Date: 01 Jun 2002 11:30:03 -0400
Organization: NASA Goddard Space Flight Center (skates.gsfc.nasa.gov)
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Simon Wright <simon@pushface.org> writes:

> Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov> writes:
> 
> > One more: require the client to pass in a Finalize procedure:
> > 
> > generic
> >    type Element is private;
> >    with procedure Finalize (Item : in out Element) is <>;
> > package Foo is
> >    type Element_array is array (1 .. 10) of Element;
> > 
> >    procedure Empty (Item : in out Element_Array);
> > 
> > end Foo;
> > 
> > Now Empty can call Finalize on each element of the array. For
> > non-controlled types, Finalize can be a null operation. This is the
> > approach I use in SAL; it allows a generic package to be
> > instantiated with the widest range of types.
> 
> I like this.
> 
> The Element probably has to be visibly (to the client) controlled, for
> her to get hold of the Finalize.

Either that, or some "Free" operation is visible. 

In SAL, I actually call this parameter "Free_Item", not "Finalize". I
was focussed more on the constrained/unconstrained and
definite/indefinite issues, which determine whether the container
elements are allocated or not, rather than on Controlled types. But
the same mechanism works for both, which is why I use it.

-- 
-- Stephe