| ------------------------------------------------------------------------------ |

| -- -- |

| -- GNAT RUN-TIME COMPONENTS -- |

| -- -- |

| -- S Y S T E M . E X P O N U -- |

| -- -- |

| -- B o d y -- |

| -- -- |

| -- Copyright (C) 1992-2021, 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. -- |

| -- -- |

| ------------------------------------------------------------------------------ |

| |

| function System.Exponu (Left : Int; Right : Natural) return Int is |

| |

| -- Note that negative exponents get a constraint error because the |

| -- subtype of the Right argument (the exponent) is Natural. |

| |

| Result : Int := 1; |

| Factor : Int := 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 |

| Result := Result * Factor; |

| end if; |

| |

| Exp := Exp / 2; |

| exit when Exp = 0; |

| Factor := Factor * Factor; |

| end loop; |

| end if; |

| |

| return Result; |

| end System.Exponu; |