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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . E X P O N U --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2025, 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. --
-- --
------------------------------------------------------------------------------
-- This function implements unsigned integer exponentiation
-- Preconditions in this unit are meant for analysis only, not for run-time
-- checking, so that the expected exceptions are raised. This is enforced
-- by setting the corresponding assertion policy to Ignore. Postconditions
-- and contract cases should not be executed at runtime as well, in order
-- not to slow down the execution of these functions.
pragma Assertion_Policy (Pre => Ignore,
Post => Ignore,
Contract_Cases => Ignore,
Ghost => Ignore);
generic
type Int is mod <>;
function System.Exponu (Left : Int; Right : Natural) return Int
with
SPARK_Mode,
Post => System.Exponu'Result = Left ** Right;
-- Calculate ``Left`` ** ``Right``. If ``Left`` is 0 then 0 is returned
-- and if ``Right`` is 0 then 1 is returned. In all other cases the result
-- is set to 1 and then computed in a loop as follows:
-- If ``Right`` is a multiple of 2 then multiply the result with ``Left``.
-- Divide ``Right`` by 2.
-- If ``Right is 0, return.
-- Multiply ``Left`` with itself.
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