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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 -- ADA.CONTAINERS.GENERIC_SORT --
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6 -- --
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7 -- B o d y --
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8 -- --
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131
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9 -- Copyright (C) 2011-2018, 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 algorithm was adapted from GNAT.Heap_Sort (see g-heasor.ad[sb])
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31
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32 with System;
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33
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34 procedure Ada.Containers.Generic_Sort (First, Last : Index_Type'Base) is
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35 type T is range System.Min_Int .. System.Max_Int;
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36
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37 function To_Index (J : T) return Index_Type;
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38 pragma Inline (To_Index);
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39
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40 function Lt (J, K : T) return Boolean;
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41 pragma Inline (Lt);
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42
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43 procedure Xchg (J, K : T);
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44 pragma Inline (Xchg);
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45
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46 procedure Sift (S : T);
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47
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48 --------------
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49 -- To_Index --
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50 --------------
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51
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52 function To_Index (J : T) return Index_Type is
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53 K : constant T'Base := Index_Type'Pos (First) + J - T'(1);
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54 begin
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55 return Index_Type'Val (K);
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56 end To_Index;
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57
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58 --------
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59 -- Lt --
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60 --------
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61
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62 function Lt (J, K : T) return Boolean is
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63 begin
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64 return Before (To_Index (J), To_Index (K));
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65 end Lt;
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66
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67 ----------
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68 -- Xchg --
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69 ----------
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70
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71 procedure Xchg (J, K : T) is
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72 begin
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73 Swap (To_Index (J), To_Index (K));
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74 end Xchg;
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75
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76 Max : T := Index_Type'Pos (Last) - Index_Type'Pos (First) + T'(1);
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77
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78 ----------
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79 -- Sift --
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80 ----------
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81
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82 procedure Sift (S : T) is
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83 C : T := S;
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84 Son : T;
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85 Father : T;
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86
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87 begin
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88 loop
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89 Son := C + C;
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90
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91 if Son < Max then
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92 if Lt (Son, Son + 1) then
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93 Son := Son + 1;
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94 end if;
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95 elsif Son > Max then
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96 exit;
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97 end if;
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98
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99 Xchg (Son, C);
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100 C := Son;
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101 end loop;
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102
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103 while C /= S loop
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104 Father := C / 2;
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105
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106 if Lt (Father, C) then
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107 Xchg (Father, C);
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108 C := Father;
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109 else
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110 exit;
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111 end if;
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112 end loop;
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113 end Sift;
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114
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115 -- Start of processing for Generic_Sort
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116
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117 begin
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118 for J in reverse 1 .. Max / 2 loop
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119 Sift (J);
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120 end loop;
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121
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122 while Max > 1 loop
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123 Xchg (1, Max);
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124 Max := Max - 1;
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125 Sift (1);
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126 end loop;
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127 end Ada.Containers.Generic_Sort;
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