| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME COMPONENTS -- |
| -- -- |
| -- S Y S T E M . E X N _ L L F -- |
| -- -- |
| -- B o d y -- |
| -- -- |
| -- Copyright (C) 1992-2005 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 2, 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. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNAT; see file COPYING. If not, write -- |
| -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- |
| -- Boston, MA 02110-1301, USA. -- |
| -- -- |
| -- As a special exception, if other files instantiate generics from this -- |
| -- unit, or you link this unit with other files to produce an executable, -- |
| -- this unit does not by itself cause the resulting executable to be -- |
| -- covered by the GNU General Public License. This exception does not -- |
| -- however invalidate any other reasons why the executable file might be -- |
| -- covered by the GNU Public License. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| package body System.Exn_LLF is |
| |
| ------------------------- |
| -- Exn_Long_Long_Float -- |
| ------------------------- |
| |
| function Exn_Long_Long_Float |
| (Left : Long_Long_Float; |
| Right : Integer) |
| return Long_Long_Float |
| is |
| Result : Long_Long_Float := 1.0; |
| Factor : Long_Long_Float := Left; |
| Exp : Integer := 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. If the low order bit or Exp is |
| -- set, multiply the result by this factor. For negative exponents, |
| -- invert result upon return. |
| |
| 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; |
| |
| return Result; |
| |
| -- Here we have a negative exponent, and we compute the result as: |
| |
| -- 1.0 / (Left ** (-Right)) |
| |
| -- Note that the case of Left being zero is not special, it will |
| -- simply result in a division by zero at the end, yielding a |
| -- correctly signed infinity, or possibly generating an overflow. |
| |
| -- Note on overflow: The coding of this routine assumes that the |
| -- target generates infinities with standard IEEE semantics. If this |
| -- is not the case, then the code below may raise Constraint_Error. |
| -- This follows the implementation permission given in RM 4.5.6(12). |
| |
| else |
| begin |
| loop |
| if Exp rem 2 /= 0 then |
| Result := Result * Factor; |
| end if; |
| |
| Exp := Exp / 2; |
| exit when Exp = 0; |
| Factor := Factor * Factor; |
| end loop; |
| |
| return 1.0 / Result; |
| end; |
| end if; |
| end Exn_Long_Long_Float; |
| |
| end System.Exn_LLF; |
