------------------------------------------------------------------------------ -- -- -- GNAT RUNTIME COMPONENTS -- -- -- -- S Y S T E M . E X N _ L L F -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2003, 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, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, 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. For positive exponents we -- multiply the result by this factor, for negative exponents, we -- Division by this factor. 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;