File : 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) 1992-2014, 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 3, 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. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
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;