1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                             E V A L _ F A T                              --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2012, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
19-- http://www.gnu.org/licenses for a complete copy of the license.          --
20--                                                                          --
21-- GNAT was originally developed  by the GNAT team at  New York University. --
22-- Extensive contributions were provided by Ada Core Technologies Inc.      --
23--                                                                          --
24------------------------------------------------------------------------------
25
26--  This package provides for compile-time evaluation of static calls to the
27--  floating-point attribute functions. It is the compile-time equivalent of
28--  the System.Fat_Gen runtime package. The coding is quite similar, as are
29--  the subprogram specs, except that the type is passed as an explicit
30--  first parameter (and used via ttypes, to obtain the necessary information
31--  about the characteristics of the type for computing the results.
32
33with Types;  use Types;
34with Uintp;  use Uintp;
35with Urealp; use Urealp;
36
37package Eval_Fat is
38
39   subtype UI is Uint;
40   --  The compile time representation of universal integer
41
42   subtype T is Ureal;
43   --  The compile time representation of floating-point values
44
45   subtype R is Entity_Id;
46   --  The compile time representation of the floating-point root type
47
48   --  The following functions perform the operation implied by their name
49   --  which corresponds to the name of the attribute which they compute.
50   --  The arguments correspond to the attribute function arguments.
51
52   function Adjacent          (RT : R; X, Towards : T)              return T;
53
54   function Ceiling           (RT : R; X : T)                       return T;
55
56   function Compose           (RT : R; Fraction : T; Exponent : UI) return T;
57
58   function Copy_Sign         (RT : R; Value, Sign : T)             return T;
59
60   function Exponent          (RT : R; X : T)                       return UI;
61
62   function Floor             (RT : R; X : T)                       return T;
63
64   function Fraction          (RT : R; X : T)                       return T;
65
66   function Leading_Part      (RT : R; X : T; Radix_Digits : UI)    return T;
67
68   function Model             (RT : R; X : T)                       return T;
69
70   function Pred              (RT : R; X : T)                       return T;
71
72   function Remainder         (RT : R; X, Y : T)                    return T;
73
74   function Rounding          (RT : R; X : T)                       return T;
75
76   function Scaling           (RT : R; X : T; Adjustment : UI)      return T;
77
78   function Succ              (RT : R; X : T)                       return T;
79
80   function Truncation        (RT : R; X : T)                       return T;
81
82   function Unbiased_Rounding (RT : R; X : T)                       return T;
83
84   --  The following global declarations are used by the Machine attribute
85
86   type Rounding_Mode is (Floor, Ceiling, Round, Round_Even);
87   for Rounding_Mode use (0, 1, 2, 3);
88   --  Used to indicate rounding mode for Machine attribute
89   --  Note that C code in gigi knows that Round_Even is 3
90
91   --  The Machine attribute is special, in that it takes an extra argument
92   --  indicating the rounding mode, and also an argument Enode that is a
93   --  node used to post warnings (e.g. if asked to convert a negative zero
94   --  on a machine for which Signed_Zeros is False).
95
96   function Machine
97     (RT    : R;
98      X     : T;
99      Mode  : Rounding_Mode;
100      Enode : Node_Id) return T;
101
102   procedure Decompose_Int
103     (RT       : R;
104      X        : T;
105      Fraction : out UI;
106      Exponent : out UI;
107      Mode     : Rounding_Mode);
108   --  Decomposes a floating-point number into fraction and exponent parts.
109   --  The Fraction value returned is an integer representing the value
110   --  Fraction * Scale, where Scale is the value (Machine_Radix_Value (RT) **
111   --  Machine_Mantissa_Value (RT)). The value is obtained by using biased
112   --  rounding (halfway cases round away from zero), round to even, a floor
113   --  operation or a ceiling operation depending on the setting of Mode (see
114   --  corresponding descriptions in Urealp).
115
116end Eval_Fat;
117