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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . I M G _ D E C --
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6 -- --
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7 -- B o d y --
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8 -- --
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145
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9 -- Copyright (C) 1992-2019, 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 -- 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 with System.Img_Int; use System.Img_Int;
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33
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34 package body System.Img_Dec is
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35
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36 -------------------
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37 -- Image_Decimal --
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38 -------------------
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39
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40 procedure Image_Decimal
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41 (V : Integer;
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42 S : in out String;
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43 P : out Natural;
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44 Scale : Integer)
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45 is
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46 pragma Assert (S'First = 1);
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47
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48 begin
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49 -- Add space at start for non-negative numbers
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50
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51 if V >= 0 then
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52 S (1) := ' ';
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53 P := 1;
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54 else
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55 P := 0;
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56 end if;
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57
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58 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
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59 end Image_Decimal;
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60
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61 ------------------------
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62 -- Set_Decimal_Digits --
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63 ------------------------
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64
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65 procedure Set_Decimal_Digits
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66 (Digs : in out String;
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67 NDigs : Natural;
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68 S : out String;
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69 P : in out Natural;
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70 Scale : Integer;
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71 Fore : Natural;
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72 Aft : Natural;
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73 Exp : Natural)
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74 is
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75 Minus : constant Boolean := (Digs (Digs'First) = '-');
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76 -- Set True if input is negative
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77
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78 Zero : Boolean := (Digs (Digs'First + 1) = '0');
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79 -- Set True if input is exactly zero (only case when a leading zero
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80 -- is permitted in the input string given to this procedure). This
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81 -- flag can get set later if rounding causes the value to become zero.
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82
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83 FD : Natural := 2;
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84 -- First digit position of digits remaining to be processed
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85
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86 LD : Natural := NDigs;
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87 -- Last digit position of digits remaining to be processed
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88
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89 ND : Natural := NDigs - 1;
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90 -- Number of digits remaining to be processed (LD - FD + 1)
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91
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92 Digits_Before_Point : Integer := ND - Scale;
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93 -- Number of digits before decimal point in the input value. This
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94 -- value can be negative if the input value is less than 0.1, so
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95 -- it is an indication of the current exponent. Digits_Before_Point
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96 -- is adjusted if the rounding step generates an extra digit.
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97
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98 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
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99 -- Digit positions after decimal point in result string
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100
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101 Expon : Integer;
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102 -- Integer value of exponent
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103
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104 procedure Round (N : Integer);
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105 -- Round the number in Digs. N is the position of the last digit to be
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106 -- retained in the rounded position (rounding is based on Digs (N + 1)
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107 -- FD, LD, ND are reset as necessary if required. Note that if the
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108 -- result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
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109 -- placed in the sign position as a result of the rounding, this is
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110 -- the case in which FD is adjusted. The call to Round has no effect
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111 -- if N is outside the range FD .. LD.
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112
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113 procedure Set (C : Character);
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114 pragma Inline (Set);
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115 -- Sets character C in output buffer
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116
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117 procedure Set_Blanks_And_Sign (N : Integer);
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118 -- Sets leading blanks and minus sign if needed. N is the number of
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119 -- positions to be filled (a minus sign is output even if N is zero
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120 -- or negative, For a positive value, if N is non-positive, then
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121 -- a leading blank is filled.
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122
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123 procedure Set_Digits (S, E : Natural);
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124 pragma Inline (Set_Digits);
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125 -- Set digits S through E from Digs, no effect if S > E
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126
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127 procedure Set_Zeroes (N : Integer);
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128 pragma Inline (Set_Zeroes);
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129 -- Set N zeroes, no effect if N is negative
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130
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131 -----------
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132 -- Round --
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133 -----------
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134
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135 procedure Round (N : Integer) is
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136 D : Character;
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137
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138 begin
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139 -- Nothing to do if rounding past the last digit we have
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140
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141 if N >= LD then
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142 return;
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143
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144 -- Cases of rounding before the initial digit
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145
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146 elsif N < FD then
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147
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148 -- The result is zero, unless we are rounding just before
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149 -- the first digit, and the first digit is five or more.
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150
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151 if N = 1 and then Digs (Digs'First + 1) >= '5' then
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152 Digs (Digs'First) := '1';
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153 else
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154 Digs (Digs'First) := '0';
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155 Zero := True;
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156 end if;
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157
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158 Digits_Before_Point := Digits_Before_Point + 1;
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159 FD := 1;
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160 LD := 1;
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161 ND := 1;
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162
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163 -- Normal case of rounding an existing digit
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164
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165 else
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166 LD := N;
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167 ND := LD - 1;
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168
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169 if Digs (N + 1) >= '5' then
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170 for J in reverse 2 .. N loop
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171 D := Character'Succ (Digs (J));
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172
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173 if D <= '9' then
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174 Digs (J) := D;
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175 return;
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176 else
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177 Digs (J) := '0';
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178 end if;
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179 end loop;
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180
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181 -- Here the rounding overflows into the sign position. That's
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182 -- OK, because we already captured the value of the sign and
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183 -- we are in any case destroying the value in the Digs buffer
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184
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185 Digs (Digs'First) := '1';
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186 FD := 1;
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187 ND := ND + 1;
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188 Digits_Before_Point := Digits_Before_Point + 1;
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189 end if;
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190 end if;
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191 end Round;
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192
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193 ---------
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194 -- Set --
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195 ---------
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196
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197 procedure Set (C : Character) is
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198 begin
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199 P := P + 1;
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200 S (P) := C;
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201 end Set;
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202
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203 -------------------------
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204 -- Set_Blanks_And_Sign --
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205 -------------------------
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206
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207 procedure Set_Blanks_And_Sign (N : Integer) is
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208 W : Integer := N;
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209
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210 begin
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211 if Minus then
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212 W := W - 1;
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213
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214 for J in 1 .. W loop
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215 Set (' ');
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216 end loop;
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217
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218 Set ('-');
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219
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220 else
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221 for J in 1 .. W loop
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222 Set (' ');
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223 end loop;
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224 end if;
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225 end Set_Blanks_And_Sign;
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226
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227 ----------------
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228 -- Set_Digits --
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229 ----------------
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230
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231 procedure Set_Digits (S, E : Natural) is
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232 begin
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233 for J in S .. E loop
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234 Set (Digs (J));
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235 end loop;
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236 end Set_Digits;
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237
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238 ----------------
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239 -- Set_Zeroes --
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240 ----------------
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241
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242 procedure Set_Zeroes (N : Integer) is
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243 begin
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244 for J in 1 .. N loop
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245 Set ('0');
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246 end loop;
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247 end Set_Zeroes;
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248
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249 -- Start of processing for Set_Decimal_Digits
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250
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251 begin
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252 -- Case of exponent given
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253
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254 if Exp > 0 then
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255 Set_Blanks_And_Sign (Fore - 1);
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256 Round (Digits_After_Point + 2);
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257 Set (Digs (FD));
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258 FD := FD + 1;
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259 ND := ND - 1;
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260 Set ('.');
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261
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262 if ND >= Digits_After_Point then
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263 Set_Digits (FD, FD + Digits_After_Point - 1);
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264 else
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265 Set_Digits (FD, LD);
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266 Set_Zeroes (Digits_After_Point - ND);
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267 end if;
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268
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269 -- Calculate exponent. The number of digits before the decimal point
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270 -- in the input is Digits_Before_Point, and the number of digits
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271 -- before the decimal point in the output is 1, so we can get the
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272 -- exponent as the difference between these two values. The one
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273 -- exception is for the value zero, which by convention has an
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274 -- exponent of +0.
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275
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276 Expon := (if Zero then 0 else Digits_Before_Point - 1);
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277 Set ('E');
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278 ND := 0;
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279
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280 if Expon >= 0 then
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281 Set ('+');
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282 Set_Image_Integer (Expon, Digs, ND);
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283 else
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284 Set ('-');
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285 Set_Image_Integer (-Expon, Digs, ND);
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286 end if;
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287
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288 Set_Zeroes (Exp - ND - 1);
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289 Set_Digits (1, ND);
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290 return;
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291
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292 -- Case of no exponent given. To make these cases clear, we use
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293 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
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294 -- A P in the example input string is an implied zero position,
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295 -- not included in the input string.
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296
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297 else
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298 -- Round at correct position
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299 -- Input: 4PP => unchanged
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300 -- Input: 400.03 => unchanged
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301 -- Input 3.4567 => 3.457
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302 -- Input: 9.9999 => 10.000
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303 -- Input: 0.PPP5 => 0.001
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304 -- Input: 0.PPP4 => 0
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305 -- Input: 0.00003 => 0
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306
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307 Round (LD - (Scale - Digits_After_Point));
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308
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309 -- No digits before point in input
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310 -- Input: .123 Output: 0.123
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311 -- Input: .PP3 Output: 0.003
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312
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313 if Digits_Before_Point <= 0 then
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314 Set_Blanks_And_Sign (Fore - 1);
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315 Set ('0');
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316 Set ('.');
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317
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318 declare
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319 DA : Natural := Digits_After_Point;
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320 -- Digits remaining to output after point
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321
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322 LZ : constant Integer := Integer'Min (DA, -Digits_Before_Point);
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323 -- Number of leading zeroes after point. Note: there used to be
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324 -- a Max of this result with zero, but that's redundant, since
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325 -- we know DA is positive, and because of the test above, we
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326 -- know that -Digits_Before_Point >= 0.
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327
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328 begin
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329 Set_Zeroes (LZ);
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330 DA := DA - LZ;
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331
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332 if DA < ND then
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333
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334 -- Note: it is definitely possible for the above condition
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335 -- to be True, for example:
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336
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337 -- V => 1234, Scale => 5, Fore => 0, After => 1, Exp => 0
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338
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339 -- but in this case DA = 0, ND = 1, FD = 1, FD + DA-1 = 0
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340 -- so the arguments in the call are (1, 0) meaning that no
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341 -- digits are output.
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342
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343 -- No obvious example exists where the following call to
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344 -- Set_Digits actually outputs some digits, but we lack a
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345 -- proof that no such example exists.
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346
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347 -- So it is safer to retain this call, even though as a
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348 -- result it is hard (or perhaps impossible) to create a
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349 -- coverage test for the inlined code of the call.
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350
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351 Set_Digits (FD, FD + DA - 1);
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352
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353 else
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354 Set_Digits (FD, LD);
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355 Set_Zeroes (DA - ND);
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356 end if;
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357 end;
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358
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359 -- At least one digit before point in input
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360
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361 else
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362 -- Less digits in input than are needed before point
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363 -- Input: 1PP Output: 100.000
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364
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365 if ND < Digits_Before_Point then
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366
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367 -- Special case, if the input is the single digit 0, then we
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368 -- do not want 000.000, but instead 0.000.
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369
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370 if ND = 1 and then Digs (FD) = '0' then
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371 Set_Blanks_And_Sign (Fore - 1);
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372 Set ('0');
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373
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374 -- Normal case where we need to output scaling zeroes
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375
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376 else
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377 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
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378 Set_Digits (FD, LD);
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379 Set_Zeroes (Digits_Before_Point - ND);
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380 end if;
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381
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382 -- Set period and zeroes after the period
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383
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384 Set ('.');
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385 Set_Zeroes (Digits_After_Point);
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386
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387 -- Input has full amount of digits before decimal point
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388
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389 else
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390 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
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391 Set_Digits (FD, FD + Digits_Before_Point - 1);
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392 Set ('.');
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393 Set_Digits (FD + Digits_Before_Point, LD);
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394 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
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395 end if;
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396 end if;
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397 end if;
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398 end Set_Decimal_Digits;
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399
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400 -----------------------
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401 -- Set_Image_Decimal --
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402 -----------------------
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403
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404 procedure Set_Image_Decimal
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405 (V : Integer;
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406 S : in out String;
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407 P : in out Natural;
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408 Scale : Integer;
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409 Fore : Natural;
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410 Aft : Natural;
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411 Exp : Natural)
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412 is
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413 Digs : String := Integer'Image (V);
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414 -- Sign and digits of decimal value
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415
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416 begin
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417 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
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418 end Set_Image_Decimal;
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419
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420 end System.Img_Dec;
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