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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT LIBRARY COMPONENTS --
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4 -- --
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5 -- A D A . C O N T A I N E R S . P R I M E _ N U M B E R S --
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6 -- --
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7 -- S p e c --
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8 -- --
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131
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9 -- Copyright (C) 2004-2018, Free Software Foundation, Inc. --
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111
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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 -- This unit was originally developed by Matthew J Heaney. --
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28 ------------------------------------------------------------------------------
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29
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30 -- This package declares the prime numbers array used to implement hashed
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31 -- containers. Bucket arrays are always allocated with a prime-number
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32 -- length (computed using To_Prime below), as this produces better scatter
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33 -- when hash values are folded.
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34
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35 package Ada.Containers.Prime_Numbers is
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36 pragma Pure;
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37
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38 type Primes_Type is array (Positive range <>) of Hash_Type;
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39
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40 Primes : constant Primes_Type :=
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41 (53, 97, 193, 389, 769,
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42 1543, 3079, 6151, 12289, 24593,
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43 49157, 98317, 196613, 393241, 786433,
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44 1572869, 3145739, 6291469, 12582917, 25165843,
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45 50331653, 100663319, 201326611, 402653189, 805306457,
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46 1610612741, 3221225473, 4294967291);
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47
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48 function To_Prime (Length : Count_Type) return Hash_Type;
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49 -- Returns the smallest value in Primes not less than Length
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50
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51 end Ada.Containers.Prime_Numbers;
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