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+------------------------------------------------------------------------------
+-- --
+-- GNAT RUN-TIME COMPONENTS --
+-- --
+-- S Y S T E M . E X P I N T --
+-- --
+-- B o d y --
+-- --
+-- Copyright (C) 1992-2009 Free Software Foundation, Inc. --
+-- --
+-- GNAT is free software; you can redistribute it and/or modify it under --
+-- terms of the GNU General Public License as published by the Free Soft- --
+-- ware Foundation; either version 3, or (at your option) any later ver- --
+-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE. --
+-- --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception, --
+-- version 3.1, as published by the Free Software Foundation. --
+-- --
+-- You should have received a copy of the GNU General Public License and --
+-- a copy of the GCC Runtime Library Exception along with this program; --
+-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
+-- <http://www.gnu.org/licenses/>. --
+-- --
+-- GNAT was originally developed by the GNAT team at New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc. --
+-- --
+------------------------------------------------------------------------------
+
+package body System.Exp_Int is
+
+ -----------------
+ -- Exp_Integer --
+ -----------------
+
+ -- Note that negative exponents get a constraint error because the
+ -- subtype of the Right argument (the exponent) is Natural.
+
+ function Exp_Integer
+ (Left : Integer;
+ Right : Natural)
+ return Integer
+ is
+ Result : Integer := 1;
+ Factor : Integer := Left;
+ Exp : Natural := Right;
+
+ begin
+ -- We use the standard logarithmic approach, Exp gets shifted right
+ -- testing successive low order bits and Factor is the value of the
+ -- base raised to the next power of 2.
+
+ -- Note: it is not worth special casing base values -1, 0, +1 since
+ -- the expander does this when the base is a literal, and other cases
+ -- will be extremely rare.
+
+ if Exp /= 0 then
+ loop
+ if Exp rem 2 /= 0 then
+ declare
+ pragma Unsuppress (All_Checks);
+ begin
+ Result := Result * Factor;
+ end;
+ end if;
+
+ Exp := Exp / 2;
+ exit when Exp = 0;
+
+ declare
+ pragma Unsuppress (All_Checks);
+ begin
+ Factor := Factor * Factor;
+ end;
+ end loop;
+ end if;
+
+ return Result;
+ end Exp_Integer;
+
+end System.Exp_Int;