Re: How to overload assignment in Ada 95?

[bbalfour@std.caci.com (Brad Balfour)]

In article <JSA.96Dec10161923@alexandria>, jsa@alexandria (Jon S Anthony) wrote:

>In article <mheaney-ya023280000912962054110001@news.ni.net>
mheaney@ni.net (Matthew Heaney) writes:
>
>> Does anyone have a rule of thumb for when a controlled type should publicly
>> derive from type Ada.Finalization.Controlled?  For example
[snip] 
>> In the former case, clients of the Unbounded_Stack have direct visibility
>> to the operations Initialize, Finalize, and Adjust.  When is this a good
>> thing?  A bad thing?
>
>"Never" (scare quotes just in case there _might_ be some odd case
>where it would make sense...)

I'd think that a "not so odd" case would be any time that your new
abstraction needed to be used anywhere that any descendent of
Ada.Finalization.Controlled would be expected (i.e., as
Ada.Finalization.Controlled'class). 

This could be via a generic formal parameter (type foo is new
Ada.Finalization.Controlled with private) or via type extension (e.g., a
list whose components are of Ada.Finalization.Controlled'class).

In order to use these, you must be known to be a (visible) extension of
Ada.Finalization.Controlled. A side effect of this is that the three
operations are visible to clients.

Brad

>Jon Anthony
>Organon Motives, Inc.
>Belmont, MA 02178
>617.484.3383
>jsa@organon.com

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