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From: mab@dst17.wdl.loral.com (Mark A Biggar)
Subject: Re: parameterless generics?
Date: 1996/07/15
Message-ID: <4seg48$o66@wdl1.wdl.lmco.com>#1/1
X-Deja-AN: 168429565
references: <4s48k9$3be$1@mhafn.production.compuserve.com>
 <4s4sns$nl4@map.mda.ca>
organization: Loral Western Development Labs
newsgroups: comp.lang.ada
Date: 1996-07-15T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <4s4sns$nl4@map.mda.ca> blaak@mda.ca (Ray Blaak) writes:
>Brian Gilbert <71413.1453@CompuServe.COM> writes:
>>Does anybody have a reason to use a generic (package or 
>>subprogram) without a parameter?  The language (Ada 83 at least) 
>>seems to allow it, but everytime the generic is instantiated it 
>>would produce an identical copy.  Comments?

Generic Child Units in Ada95 will almost always be like this

>Another possible reason is to make functionality "active" only when you need
>it. Consider:
>
>package Entity is
>  type Object is private;
>
>  procedure Low_Impact_Operation (On_The_Object : in out Object);
>
>  generic
>  package Fancy_Processing_Involving_A_Huge_Link_Enclosure is
>    procedure Do_It_At_Your_Own_Risk (To_Me : in out Object);
>  end Fancy_Processing_Involving_A_Huge_Link_Enclosure;
>end Entity;
>It could be that one application (say offline report generation) only needs a
>few features and a small link enclosure. The real system might be involved in a
>complex architecture with a large link enclosure. By having the extra
>operations in a generic, there should be no executable code generated for it
>until instantiation. This would be dependent on how you wrote the generic and
>how the compiler implements generics.

This usage is of course complete subsumed by Child Packages.

--
Mark Biggar
mab@wdl.lmco.com