Re: How to access an array using two different indexing schemes

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:ovdvnm$3dt$1@gioia.aioe.org...
> On 2017-11-26 02:07, Jerry wrote:
>> On Friday, November 24, 2017 at 4:38:10 PM UTC-7, Jerry wrote:
>>> I frequently allocate memory for arrays from the heap, as discussed 
>>> previously on this list, like this:
>>>
>>> with Ada.Numerics.Long_Real_Arrays; use Ada.Numerics.Long_Real_Arrays;
>>> procedure Double_Array_2 is
>>>      type Real_Vector_Access is access Real_Vector;
>>>      x_Ptr : Real_Vector_Access := new Real_Vector(-4 .. 3);
>>>          x : Real_Vector renames x_Ptr.all;
>>>      y_Ptr : Real_Vector_Access := new Real_Vector(0 .. 7);
>>>          y : Real_Vector renames y_Ptr.all;
>>> begin
>>>      null;
>>> end Double_Array_2;
>>>
>>> How would I use the 'Address trick in this situation?

Don't. Just type convert X as needed:

with Ada.Numerics.Long_Real_Arrays; use Ada.Numerics.Long_Real_Arrays;
procedure Double_Array_2 is
      type Real_Vector_Access is access Real_Vector;
      x_Ptr : Real_Vector_Access := new Real_Vector(-4 .. 3);
             x : Real_Vector renames x_Ptr.all;
--   y_Ptr : Real_Vector_Access := new Real_Vector(0 .. 7);
-->> This is allocating a new object for Real_Vector, which I don't think 
you want to do.
      subtype RV0_7 is Real_Vector(0..7);
      procedure Do_Y (Y : in out RV0_7) is
      begin
           -- Operations on Y.
      end Do_Y;

     begin
          Do_Y (RV0_7(X));
     end Double_Array_2;

If you used the Address clause hack here, you'd be subject to termination. 
GIGO.

                                  Randy.