Re: Gnat 2013 is out!

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Thu, 30 May 2013 14:53:43 -0500, Randy Brukardt wrote:

> "Adam Beneschan" <adam@irvine.com> wrote in message 
> news:32d94173-533a-471e-95a0-abb73a6cdcc2@googlegroups.com...
> On Wednesday, May 29, 2013 3:39:44 PM UTC-7, Randy Brukardt wrote:
> 
>>I've always wanted some kind of feature in Ada that would allow a caller to 
>>provide a
>>"dummy" for OUT parameters, without having to declare a new variable.  The 
>>compiler
>>would allocate a temporary object (and a separate one for each use of a 
>>"dummy") and
>>then discard it after the call.  It wouldn't work well when parameter types 
>>are
>>unconstrained array or discriminant records, though.
> 
> Hmm, that seems like a good idea to me. But what would the syntax be? <> 
> maybe?
> 
>          My_Proc (Obj1, Obj2, Result => <>);

As well as function results:

   <> := My_Func (Obj1, Obj2); -- I do this for side effects!

Back in 90's I thought about null statement:

   null My_Func (Obj1, Obj2);

But for procedures it won't work:

   My_Proc (Obj1, Obj2, Result => null); -- Ambiguous

> I tried to work out a solution based on default parameters for all modes 
> (which would provide your dummy result along with other uses), but it didn't 
> work out very well. The main problem was that the default objects usually 
> had to be globals, and that could cause an unsafe use of shared variables in 
> a tasking environment.

These are two different cases. One is when the default is a named object,
another is when the default is an anonymous object allocated on the stack.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de