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

[Jerry <list_email@icloud.com>]

On Friday, November 24, 2017 at 10:37:30 AM UTC-7, A. Cervetti wrote:
> use attribute 'Address:
> 
> with Ada.Text_IO; use Ada.Text_IO;
> with Ada.Float_Text_IO; use Ada.Float_Text_IO;
> with Ada.Numerics.Generic_Real_Arrays;
> 
> procedure Double_Array is
>    package Real_Array is new Ada.Numerics.Generic_Real_Arrays(Float);
>    use Real_Array;
>    
>    x : Real_Vector(0 .. 4) := (1.0, 2.0, 3.0, 4.0, 5.0);
>    y : Real_Vector(1 .. 5);
>    for Y'Address use X'Address; -- <<<<<<<<<<<<<<<<<<<<
>    
> begin
>    X(0) := 20.0;
>    Put(X(0), 0, 0, 0); New_Line;
>    Put(Y(1), 0, 0, 0); New_Line;
> end Double_Array;

Nice. Thank you. That solves the "version control" or "bookkeeping" problem, but it still requires allocating double memory, for y.

I had hoped to use an access variable for the role of y so that only a tiny amount of additional memory would be required, and somehow do a type conversion of the y-pointer as it points at x, but I haven't been able yet to figure out how to do the pointer type conversion. Is this even possible?

Jerry