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 --                                                                          --
  10 --          Copyright (C) 1992-1999 Free Software Foundation, Inc.          --
  11 --                                                                          --
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  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
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  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
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  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
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  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNAT was originally developed  by the GNAT team at  New York University. --
  31 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This package provides a powers of ten table used for real conversions
  36
  37 package System.Powten_Table is
  38 pragma Pure (Powten_Table);
  39
  40    Maxpow : constant := 22;
  41    --  The number of entries in this table is chosen to include powers of ten
  42    --  that are exactly representable with long_long_float. Assuming that on
  43    --  all targets we have 53 bits of mantissa for the type, the upper bound is
  44    --  given by 53/(log 5). If the scaling factor for a string is greater than
  45    --  Maxpow, it can be obtained by several multiplications, which is less
  46    --  efficient than with a bigger table, but avoids anomalies at end points.
  47
  48    Powten : constant array (0 .. Maxpow) of Long_Long_Float :=
  49       (00 => 1.0E+00,
  50        01 => 1.0E+01,
  51        02 => 1.0E+02,
  52        03 => 1.0E+03,
  53        04 => 1.0E+04,
  54        05 => 1.0E+05,
  55        06 => 1.0E+06,
  56        07 => 1.0E+07,
  57        08 => 1.0E+08,
  58        09 => 1.0E+09,
  59        10 => 1.0E+10,
  60        11 => 1.0E+11,
  61        12 => 1.0E+12,
  62        13 => 1.0E+13,
  63        14 => 1.0E+14,
  64        15 => 1.0E+15,
  65        16 => 1.0E+16,
  66        17 => 1.0E+17,
  67        18 => 1.0E+18,
  68        19 => 1.0E+19,
  69        20 => 1.0E+20,
  70        21 => 1.0E+21,
  71        22 => 1.0E+22);
  72
  73 end System.Powten_Table;