AW: Why does this work? (overloads)

["Grein, Christoph (Fa. ESG)" <Christoph.Grein@eurocopter.com>]

Try this. Not very elegant, but works.

with Ada.Exceptions;

with Ada.Text_IO, Ada.Float_Text_IO;
use  Ada.Text_IO, Ada.Float_Text_IO;

with Ada.Unchecked_Conversion;

procedure Test_it is

  N: constant := 10;

  type Vector is array (Integer range <>) of Float;
  -- Fat pointers don't work (include bounds).
  -- type Vector_Ptr is access all Vector;
  -- subtype Vector_Ptr_1   is Vector_Ptr (  1 .. N      );
  -- subtype Vector_Ptr_101 is Vector_Ptr (101 .. N + 100);

  -- Thin pointers (don't include bounds):
  type Vector_Ptr_1   is access all Vector (  1 .. N      );
  type Vector_Ptr_101 is access all Vector (101 .. N + 100);

  function Convert is new
    Ada.Unchecked_Conversion (Vector_Ptr_1, Vector_Ptr_101);

  X: aliased Vector (1 .. N);  -- constrained nominal subtype
  P: Vector_Ptr_1   := X'Access;
  Q: Vector_Ptr_101 := Convert (P);

begin

  for i in X'Range loop
    X (i) := Float (i);
  end loop;

  for i in P'Range loop
    Put (Integer'Image (i));  Put (P (i));  New_Line;
  end loop;

  for i in Q'Range loop
    Put (Integer'Image (i));  Put (Q (i));  New_Line;
  end loop;

exception
  when Exc: others =>
    Put_Line ("Unexpected exception " &
              Ada.Exceptions.Exception_Name (Exc));

end Test_it;

-----Ursprüngliche Nachricht-----
Jerry wrote:

Good point. However, it uses twice the memory, and worse, changes made
in A are not reflected in B without repeating the assignment A := B
(correct?) and vice versa. My Pascal trick had neither of these
problems yet carried boundary checking using either name.

Maybe there's a way to do this using unrestricted_access variables of
GNAT.

Jerry