Re: Extended return question

[Adam Beneschan <adam@irvine.com>]

On Jul 10, 12:32 am, Dale Stanbrough <MrNoS...@bigpoop.net.au> wrote:
> Georg Bauhaus wrote:
> > Dale Stanbrough wrote:
> > > The purpose of an extended return is to create the values in-situ
> > > without copying.
>
> > _Limited_ objects can be initialized in situ by an aggregate
> > or function call  ... :-)
>
> Ah, thanks.  I had misread John Barnes comments on this. Why such a
> restriction? Why not allow it for all extended returns on all types?

For nonlimited types, function calls work the same way they've always
worked since Ada 83.  The function call builds an anonymous object.
In your example, since you're using an assignment, the anonymous
object is then assigned into Destination.  But of course, if the
function raises an exception, the assignment never takes place.

This isn't too different from this situation, which has always existed
since Ada 83:

   Destination := (1 => Func1, 2 => Func2, 3 => Func3, 4 => Func4);

If Func1 and Func2 complete normally, but Func3 raises an exception,
*no* elements of Destination are changed.  Extended return is no
different.  Function calls still involve anonymous objects to hold the
function result, and extended return doesn't change that.

Hope this helps,

                              -- Adam