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From: "Ayende Rahien" <Dont@spam.me>
Newsgroups: comp.lang.ada
Subject: Re: Problem understanding procedure Adjust(.
Date: Sat, 7 Apr 2001 15:51:19 +0200
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Date: 2001-04-07T15:51:19+02:00
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"Mark Biggar" <mark.a.biggar@home.com> wrote in message
news:3ACF1A25.E059BCBC@home.com...
> Ayende Rahien wrote:
> > And I'm trying to read this package's body
> > (http://adahome.com/Tutorials/Lovelace/genestac.adb)
> > My problem is with this procedure:
> >     procedure Adjust(Object : in out Stack) is
> >     -- ...
> >     end Adjust;
> >
> > As far as I understand, this procedure is called if I do assignment on
> > stacks (which is what this package is about).
> > If I got it correctly, when I do:
> > stack1 := stack2;
> > The Adjust procedure will be called.
> >
> > Now, Object seems to be the variable on the right side (stack2), if so,
how
> > come that stack1 get a new copy of the contents of stack2, without
stack2
> > being affected?
> > Object is an in ou parameter, this mean that changes that are done
inside
> > the procedure will persist after the procedure terminate, right?
> > So how do stack1 get a copy of stack2 without destroy stack2?
>
> No, Adjust is called on stack1, after a bitwise copy is made
> of stack2.  The intent is that Adjust can do things like deep copies or
> reference count changes.

Okay, that clear things up.

> > Another question, when using new, how do I find out if the memory
allocation
> > was unsuccessful? I assume that an exception is raise, is this correct?
If
> > so, what is it?
>
> STORAGE_ERROR

Thanks.