Re: Gnat 2013 is out!

[Stefan.Lucks@uni-weimar.de]

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On Thu, 30 May 2013, Randy Brukardt wrote:

> "Adam Beneschan" <adam@irvine.com> wrote in message
>
>> 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 => <>);
>

This has two issues:

   1. This won't work if the type of Result is unconstrained, as, e.g., in

      procedure My_Proc(Obj1, Obj2: String; Result : String);

   2. This would sometimes break overload resolution -- which procedure
      should be called by "My_Proc (Obj1, Obj2, Result => <>);" if there
      happens to be another procedure in scope, such as

      procedure My_Proc(Obj1, Obj2: String; Result : Unbounded_String);

I'd suggest


         My_Proc (Obj1, Obj2, Result => String(1 .. 80));

or in general

         My_Proc (Obj1, Obj2, Result => type Name_of_Type);

as syntactic sugar for

    declare
      Dummy : Name_Of_Type;
    begin
      My_Proc (Obj1, Obj2, Result => type Name_of_Type);
    end;





------  I  love  the  taste  of  Cryptanalysis  in  the morning!  ------
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--Stefan.Lucks (at) uni-weimar.de, Bauhaus-Universität Weimar, Germany--