Re: Problem understanding procedure Adjust(.

[Mark Biggar <mark.a.biggar@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.
 
> 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