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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Interesting effects in array renaming
Date: Sun, 22 Jun 2003 16:52:22 +0200
Organization: At home
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Date: 2003-06-22T16:52:22+02:00
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---------- test.adb
with Ada.Text_IO;  use Ada.Text_IO;

procedure Test is
   type Some_Array is array (Integer range <>) of Integer;

   procedure Foo (X : Some_Array) is
      subtype Constrained is Some_Array (1..X'Length);
      XX : Constrained renames X;
   begin
      Put_Line
      (  "XX'Range:"
      &  Integer'Image (XX'First)
      &  ".."
      &  Integer'Image (XX'Last)
      &  ", Constrained'Range:"
      &  Integer'Image (Constrained'First)
      &  ".."
      &  Integer'Image (Constrained'Last)
      );
   end Foo;

   Object : Some_Array (-3..2) := (-3, -2, -1, 0, 1, 2);
begin
   Foo (Object);
end Test;
---------- test.adb

Surprisingly the above produces different ranges for XX and its declared 
subtype. Isn't something wrong here?

I would expect either

1. XX'Range = Constrained'Range and indices are shifted

or

2. Raising Constraint_Error while renaming. How else could the compiler 
remove range checks for

X : Array_Subtype ...

for I in Array_Subtype'Range loop
   X (I) ...

-- 
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de