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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 -- E V A L _ F A T --
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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) 1992-2012, 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. See the GNU General Public License --
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17 -- for more details. You should have received a copy of the GNU General --
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18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
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19 -- http://www.gnu.org/licenses for a complete copy of the license. --
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20 -- --
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21 -- GNAT was originally developed by the GNAT team at New York University. --
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22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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23 -- --
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24 ------------------------------------------------------------------------------
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25
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26 -- This package provides for compile-time evaluation of static calls to the
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27 -- floating-point attribute functions. It is the compile-time equivalent of
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28 -- the System.Fat_Gen runtime package. The coding is quite similar, as are
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29 -- the subprogram specs, except that the type is passed as an explicit
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30 -- first parameter (and used via ttypes, to obtain the necessary information
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31 -- about the characteristics of the type for computing the results.
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32
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33 with Types; use Types;
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34 with Uintp; use Uintp;
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35 with Urealp; use Urealp;
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36
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37 package Eval_Fat is
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38
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39 subtype UI is Uint;
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40 -- The compile time representation of universal integer
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41
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42 subtype T is Ureal;
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43 -- The compile time representation of floating-point values
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44
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45 subtype R is Entity_Id;
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46 -- The compile time representation of the floating-point root type
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47
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48 -- The following functions perform the operation implied by their name
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49 -- which corresponds to the name of the attribute which they compute.
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50 -- The arguments correspond to the attribute function arguments.
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51
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52 function Adjacent (RT : R; X, Towards : T) return T;
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53
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54 function Ceiling (RT : R; X : T) return T;
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55
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56 function Compose (RT : R; Fraction : T; Exponent : UI) return T;
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57
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58 function Copy_Sign (RT : R; Value, Sign : T) return T;
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59
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60 function Exponent (RT : R; X : T) return UI;
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61
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62 function Floor (RT : R; X : T) return T;
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63
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64 function Fraction (RT : R; X : T) return T;
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65
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66 function Leading_Part (RT : R; X : T; Radix_Digits : UI) return T;
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67
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68 function Model (RT : R; X : T) return T;
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69
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70 function Pred (RT : R; X : T) return T;
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71
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72 function Remainder (RT : R; X, Y : T) return T;
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73
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74 function Rounding (RT : R; X : T) return T;
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75
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76 function Scaling (RT : R; X : T; Adjustment : UI) return T;
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77
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78 function Succ (RT : R; X : T) return T;
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79
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80 function Truncation (RT : R; X : T) return T;
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81
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82 function Unbiased_Rounding (RT : R; X : T) return T;
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83
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84 -- The following global declarations are used by the Machine attribute
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85
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86 type Rounding_Mode is (Floor, Ceiling, Round, Round_Even);
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87 for Rounding_Mode use (0, 1, 2, 3);
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88 -- Used to indicate rounding mode for Machine attribute
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89 -- Note that C code in gigi knows that Round_Even is 3
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90
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91 -- The Machine attribute is special, in that it takes an extra argument
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92 -- indicating the rounding mode, and also an argument Enode that is a
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93 -- node used to post warnings (e.g. if asked to convert a negative zero
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94 -- on a machine for which Signed_Zeros is False).
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95
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96 function Machine
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97 (RT : R;
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98 X : T;
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99 Mode : Rounding_Mode;
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100 Enode : Node_Id) return T;
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101
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102 procedure Decompose_Int
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103 (RT : R;
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104 X : T;
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105 Fraction : out UI;
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106 Exponent : out UI;
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107 Mode : Rounding_Mode);
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108 -- Decomposes a floating-point number into fraction and exponent parts.
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109 -- The Fraction value returned is an integer representing the value
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110 -- Fraction * Scale, where Scale is the value (Machine_Radix_Value (RT) **
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111 -- Machine_Mantissa_Value (RT)). The value is obtained by using biased
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112 -- rounding (halfway cases round away from zero), round to even, a floor
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113 -- operation or a ceiling operation depending on the setting of Mode (see
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114 -- corresponding descriptions in Urealp).
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115
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116 end Eval_Fat;
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