annotate gcc/ada/libgnat/s-powtab.ads @ 131:84e7813d76e9

gcc-8.2
author mir3636
date Thu, 25 Oct 2018 07:37:49 +0900
parents 04ced10e8804
children 1830386684a0
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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- S Y S T E M . P O W T E N _ T A B L E --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 1992-2018, Free Software Foundation, Inc. --
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package provides a powers of ten table used for real conversions
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33
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34 package System.Powten_Table is
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35 pragma Pure;
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36
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37 Maxpow : constant := 22;
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38 -- The number of entries in this table is chosen to include powers of ten
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39 -- that are exactly representable with long_long_float. Assuming that on
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40 -- all targets we have 53 bits of mantissa for the type, the upper bound is
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41 -- given by 53/(log 5). If the scaling factor for a string is greater than
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42 -- Maxpow, it can be obtained by several multiplications, which is less
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43 -- efficient than with a bigger table, but avoids anomalies at end points.
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44
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45 Powten : constant array (0 .. Maxpow) of Long_Long_Float :=
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46 (00 => 1.0E+00,
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47 01 => 1.0E+01,
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48 02 => 1.0E+02,
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49 03 => 1.0E+03,
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50 04 => 1.0E+04,
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51 05 => 1.0E+05,
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52 06 => 1.0E+06,
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53 07 => 1.0E+07,
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54 08 => 1.0E+08,
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55 09 => 1.0E+09,
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56 10 => 1.0E+10,
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57 11 => 1.0E+11,
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58 12 => 1.0E+12,
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59 13 => 1.0E+13,
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60 14 => 1.0E+14,
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61 15 => 1.0E+15,
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62 16 => 1.0E+16,
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63 17 => 1.0E+17,
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64 18 => 1.0E+18,
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65 19 => 1.0E+19,
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66 20 => 1.0E+20,
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67 21 => 1.0E+21,
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68 22 => 1.0E+22);
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69
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70 end System.Powten_Table;