Re: Aliasing or referencing assignment

["Steve" <nospam_steved94@comcast.net>]

"David Trudgett" <wpower@zeta.org.au.nospamplease> wrote in message 
news:m3slwf3xcy.fsf@rr.trudgett...
>
> I'm having a little difficulty with assign by reference and assign by
> value (copy) semantics in a piece of code I'm working on. In the
> chunk of code that follows below, I want to avoid repeating
> "Self.List(Opponent_Win, Can_I_Play)" many times, and just replace it
> with a variable name like "C".
>
> "Self.List(Opponent_Win, Can_I_Play)" returns a Charles container
> library Vector of Unbounded_String. The assignment:
>
>      C := Self.List(Opponent_Win, Can_I_Play); -- "List" is 2D array
>

How about something like:

  declare
      C : ListElementType renames Self.List(Opponent_Win, Can_I_Play);
  begin
        ... code that uses C ...
       Append( C, To_Unbounded_String( "Blah blah" ) );
  end;


Steve
(The Duck)

> is ineffective in doing what I want because it is doing a value
> copy. I've tried to turn the type definition of "C" into an access
> type, but with no success. I also tried the "To_Access" function (in
> charles.vectors.unbounded), but that returns a reference to an
> "Element_Array" and not a Container_Type with which I can use
> "Append".
>
> Anyway, here is the code:
>
>
>
>   procedure Initialize (Self : in out Comments)
>   is
>      C : String_List.Container_Type;
>      package Random_Integer is new Ada.Numerics.Discrete_Random(Integer);
>      use Random_Integer;
>      G : Generator;
>   begin
>
>      Reset(G);
>      Ada.Numerics.Float_Random.Reset(Self.PRNG, Random(G));
>
>      -- OPPONENT WIN COMMENTS
>      -- Can I Play difficulty
>      C := Self.List(Opponent_Win, Can_I_Play);
>
>      Append
>        (C, To_Unbounded_String
>         ("You're too good for me"));
>      Append
>        (C, To_Unbounded_String
>         ("How did you manage that?"));
>
>      ... and so on.
>
> That works if I then finish with:
>
>      Self.List(Opponent_Win, Can_I_Play) := C;
>
>
> But that's copy overhead I want to avoid (fifteen times, what's
> more). For the time being, I've just replaced all of the "C"s in the
> Append procedure calls with "Self.List(Opponent_Win, Can_I_Play)" (and
> variations thereof further down).
>
> How can I make "C" act like a reference to the Unbounded_String Vector?
>
> Also, is the 'To_Unbounded_String("this is a string")' really
> necessary? I thought I read in the ARM that string literals were
> defined for all the string types.
>
> Thanks,
>
> David
>
>
> P.S.
>
> Later on, I will probably read these comments from an XML file, but
> for now I'm just hard coding them into the program.
>
>
> -- 
>
> David Trudgett
> http://www.zeta.org.au/~wpower/
>
> FORTH IF HONK THEN
>