1------------------------------------------------------------------------------
2--                                                                          --
3--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
4--                                                                          --
5--    S Y S T E M . V E C T O R S . B O O L E A N _ O P E R A T I O N S     --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 2002-2009, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package contains functions for runtime operations on boolean vectors
33
34package System.Vectors.Boolean_Operations is
35   pragma Pure;
36
37   --  Although in general the boolean operations on arrays of booleans are
38   --  identical to operations on arrays of unsigned words of the same size,
39   --  for the "not" operator this is not the case as False is typically
40   --  represented by 0 and true by 1.
41
42   function "not" (Item : Vectors.Vector) return Vectors.Vector;
43
44   --  The three boolean operations "nand", "nor" and "nxor" are needed
45   --  for cases where the compiler moves boolean array operations into
46   --  the body of the loop that iterates over the array elements.
47
48   --  Note the following equivalences:
49   --    (not X) or  (not Y)  =  not (X and Y)  =  Nand (X, Y)
50   --    (not X) and (not Y)  =  not (X or Y)   =  Nor  (X, Y)
51   --    (not X) xor (not Y)  =  X xor Y
52   --    X       xor (not Y)  =  not (X xor Y)  =  Nxor (X, Y)
53
54   function Nand (Left, Right : Boolean) return Boolean;
55   function Nor  (Left, Right : Boolean) return Boolean;
56   function Nxor (Left, Right : Boolean) return Boolean;
57
58   function Nand (Left, Right : Vectors.Vector) return Vectors.Vector;
59   function Nor (Left, Right : Vectors.Vector) return Vectors.Vector;
60   function Nxor (Left, Right : Vectors.Vector) return Vectors.Vector;
61
62   pragma Inline_Always ("not");
63   pragma Inline_Always (Nand);
64   pragma Inline_Always (Nor);
65   pragma Inline_Always (Nxor);
66end System.Vectors.Boolean_Operations;
67