1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . E X N _ I N T --
9 -- Copyright (C) 1992-2005 Free Software Foundation, Inc. --
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 2, 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. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 package body System.Exn_Int is
40 function Exn_Integer (Left : Integer; Right : Natural) return Integer is
41 pragma Suppress (Division_Check);
42 pragma Suppress (Overflow_Check);
44 Result : Integer := 1;
45 Factor : Integer := Left;
46 Exp : Natural := Right;
49 -- We use the standard logarithmic approach, Exp gets shifted right
50 -- testing successive low order bits and Factor is the value of the
51 -- base raised to the next power of 2.
53 -- Note: it is not worth special casing base values -1, 0, +1 since
54 -- the expander does this when the base is a literal, and other cases
55 -- will be extremely rare.
59 if Exp rem 2 /= 0 then
60 Result := Result * Factor;
65 Factor := Factor * Factor;