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From: christoph.grein@eurocopter.com
Newsgroups: comp.lang.ada
Subject: Re: another way to shoot yourself in the foot?
Date: Fri, 20 Jun 2008 03:05:29 -0700 (PDT)
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> --- Factory ads ---
> with Named;
> with Some;
>
> package Factory is
> =A0 =A0function Create(class: String; name: String) return
> Named.Object'Class;
> end Factory;
>
> --- Factory.adb ---
>
> with Ada.Strings.Fixed; use Ada.Strings.Fixed;
> with Some;
>
> package body Factory is
> =A0 =A0--- this one is ugly, but in sake of simplicity ...
> =A0 =A0function Create(class: String; name: String) return
> Named.Object'Class is
> =A0 =A0begin
> =A0 =A0 =A0 if Index(class, "Some") /=3D 0 then
> =A0 =A0 =A0 =A0 =A0return Some.Create(name);
> =A0 =A0 =A0 end if;
> =A0 =A0 =A0 raise Program_Error with "Unknown class " & class;
> =A0 =A0end;
> end Factory;

Since Some.Object is limited, Factory must construct in place. The
normal return statement produces a copy (I guess there should be a
warning here - no compiler bug, since the RM has nothing to say about
warnings). So use the extended return statement as in Some.Create.

(This is just a guess, dunno if it helps.)