gcc/ada/libgnat/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) 1992-2018, Free Software Foundation, Inc.         --
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  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
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  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
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  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This package provides a powers of ten table used for real conversions
  33
  34 package System.Powten_Table is
  35    pragma Pure;
  36
  37    Maxpow : constant := 22;
  38    --  The number of entries in this table is chosen to include powers of ten
  39    --  that are exactly representable with long_long_float. Assuming that on
  40    --  all targets we have 53 bits of mantissa for the type, the upper bound is
  41    --  given by 53/(log 5). If the scaling factor for a string is greater than
  42    --  Maxpow, it can be obtained by several multiplications, which is less
  43    --  efficient than with a bigger table, but avoids anomalies at end points.
  44
  45    Powten : constant array (0 .. Maxpow) of Long_Long_Float :=
  46       (00 => 1.0E+00,
  47        01 => 1.0E+01,
  48        02 => 1.0E+02,
  49        03 => 1.0E+03,
  50        04 => 1.0E+04,
  51        05 => 1.0E+05,
  52        06 => 1.0E+06,
  53        07 => 1.0E+07,
  54        08 => 1.0E+08,
  55        09 => 1.0E+09,
  56        10 => 1.0E+10,
  57        11 => 1.0E+11,
  58        12 => 1.0E+12,
  59        13 => 1.0E+13,
  60        14 => 1.0E+14,
  61        15 => 1.0E+15,
  62        16 => 1.0E+16,
  63        17 => 1.0E+17,
  64        18 => 1.0E+18,
  65        19 => 1.0E+19,
  66        20 => 1.0E+20,
  67        21 => 1.0E+21,
  68        22 => 1.0E+22);
  69
  70 end System.Powten_Table;