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Date: Sat, 01 Sep 2007 16:15:44 +0200
From: Georg Bauhaus <bauhaus.rm.tsoh@maps.futureapps.de>
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Subject: Re: Self pointer in limited record
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Date: 2007-09-01T16:10:48+02:00
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Dmitry A. Kazakov wrote:
> On Sat, 01 Sep 2007 15:33:09 +0200, Georg Bauhaus wrote:
> 
>> (The true O-O programmer might suggest that we should simply
>> pass an additional object-as-module parameter to every
>> package subprogram... )
> 
> Yes, it is better to keep packages stateless.

Though by using tagged objects for a module
and not a stateful package, you will dismiss a few
properties of packages that can be helpful when
modeling singleton modules:

1 - If there is just one object in the problem domain a
package is a perfect match and will be straight forward, safe,
and simple to implement. No need to worry about static and
dynamic scopes of module-objects passed around because
there is just this one named package for the problem
domain object.

2 - Nesting packages is an option, a distinguishing feature
of Ada IMO; a package nested inside a subprogram is a
simple solution to the life cycle problem of module style
objects.
For example, when a singleton object is needed only while
a subprogram S is executing, why not just create a simple
package within S, that is, right where it is needed, and
not anywhere else?