gcc/ada/s-powtab.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                  S Y S T E M . P O W T E N _ T A B L E                   --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2005 Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides a powers of ten table used for real conversions
  35
  36 package System.Powten_Table is
  37    pragma Pure;
  38
  39    Maxpow : constant := 22;
  40    --  The number of entries in this table is chosen to include powers of ten
  41    --  that are exactly representable with long_long_float. Assuming that on
  42    --  all targets we have 53 bits of mantissa for the type, the upper bound is
  43    --  given by 53/(log 5). If the scaling factor for a string is greater than
  44    --  Maxpow, it can be obtained by several multiplications, which is less
  45    --  efficient than with a bigger table, but avoids anomalies at end points.
  46
  47    Powten : constant array (0 .. Maxpow) of Long_Long_Float :=
  48       (00 => 1.0E+00,
  49        01 => 1.0E+01,
  50        02 => 1.0E+02,
  51        03 => 1.0E+03,
  52        04 => 1.0E+04,
  53        05 => 1.0E+05,
  54        06 => 1.0E+06,
  55        07 => 1.0E+07,
  56        08 => 1.0E+08,
  57        09 => 1.0E+09,
  58        10 => 1.0E+10,
  59        11 => 1.0E+11,
  60        12 => 1.0E+12,
  61        13 => 1.0E+13,
  62        14 => 1.0E+14,
  63        15 => 1.0E+15,
  64        16 => 1.0E+16,
  65        17 => 1.0E+17,
  66        18 => 1.0E+18,
  67        19 => 1.0E+19,
  68        20 => 1.0E+20,
  69        21 => 1.0E+21,
  70        22 => 1.0E+22);
  71
  72 end System.Powten_Table;