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

[Shark8 <onewingedshark@gmail.com>]

On Tuesday, November 28, 2017 at 9:57:48 PM UTC-7, Jerry wrote:
> 
> Your method shows how to pass the re-dimensioned array to a subprogram for processing with a typecast. But I also need to process the array in the same program that the subtype is declared. How would I do the typecast without allocating more memory?
> 
> Something like this:
> 
> procedure Doubly_Indexed_Array is
>    declare x with dimensions (0 .. 4)
>    declare y with dimensions (1 .. 5) using the same memory as x but
> 	                              accessed with different indices
> begin
>    x(0) := 10.0;
>    y(3) := 20.0;
>    print x(0) resulting in 10.0
>    print y(1) resulting in 10.0
>    print x(2) resulting in 20.0
>    print y(3) resulting in 20.0
> end Doubly_Indexed_Array;

Subtype Real is Float range Float'Range; -- Get rid of non-numeric.
Type General_Real_Array is Array(Integer range <>) of Real;

Procedure Do_Stuffs( Data : in out General_Real_Array ) is
  Subtype Indexing is General_Real_Array(1..Data'Length);
  Subtype Offset   is General_Real_Array(0..Integer'Pred(Data'Length));
  
  Indexed  : Indexing renames Data;
  Offseted : Offset renames Data;
Begin
  -- Stuffs!
  null;
End Do_Stuffs;