Mercurial > hg > CbC > CbC_gcc
comparison gcc/ada/libgnat/s-rannum.ads @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
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children | 84e7813d76e9 |
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1 ------------------------------------------------------------------------------ | |
2 -- -- | |
3 -- GNAT RUN-TIME COMPONENTS -- | |
4 -- -- | |
5 -- S Y S T E M . R A N D O M _ N U M B E R S -- | |
6 -- -- | |
7 -- S p e c -- | |
8 -- -- | |
9 -- Copyright (C) 2007-2017, 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. -- | |
17 -- -- | |
18 -- As a special exception under Section 7 of GPL version 3, you are granted -- | |
19 -- additional permissions described in the GCC Runtime Library Exception, -- | |
20 -- version 3.1, as published by the Free Software Foundation. -- | |
21 -- -- | |
22 -- You should have received a copy of the GNU General Public License and -- | |
23 -- a copy of the GCC Runtime Library Exception along with this program; -- | |
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- | |
25 -- <http://www.gnu.org/licenses/>. -- | |
26 -- -- | |
27 -- GNAT was originally developed by the GNAT team at New York University. -- | |
28 -- Extensive contributions were provided by Ada Core Technologies Inc. -- | |
29 -- -- | |
30 ------------------------------------------------------------------------------ | |
31 | |
32 -- Extended pseudo-random number generation | |
33 | |
34 -- This package provides a type representing pseudo-random number generators, | |
35 -- and subprograms to extract various uniform distributions of numbers | |
36 -- from them. It also provides types for representing initialization values | |
37 -- and snapshots of internal generator state, which permit reproducible | |
38 -- pseudo-random streams. | |
39 | |
40 -- The generator currently provided by this package has an extremely long | |
41 -- period (at least 2**19937-1), and passes the Big Crush test suite, with the | |
42 -- exception of the two linear complexity tests. Therefore, it is suitable | |
43 -- for simulations, but should not be used as a cryptographic pseudo-random | |
44 -- source without additional processing. | |
45 | |
46 -- Note: this package is in the System hierarchy so that it can be directly | |
47 -- used by other predefined packages. User access to this package is via | |
48 -- the package GNAT.Random_Numbers (file g-rannum.ads), which also extends | |
49 -- its capabilities. The interfaces are different so as to include in | |
50 -- System.Random_Numbers only the definitions necessary to implement the | |
51 -- standard random-number packages Ada.Numerics.Float_Random and | |
52 -- Ada.Numerics.Discrete_Random. | |
53 | |
54 -- Note: this package is marked SPARK_Mode Off, because functions Random work | |
55 -- by side-effect to change the value of the generator, hence they should not | |
56 -- be called from SPARK code. | |
57 | |
58 with Interfaces; | |
59 | |
60 package System.Random_Numbers with | |
61 SPARK_Mode => Off | |
62 is | |
63 type Generator is limited private; | |
64 -- Generator encodes the current state of a random number stream, it is | |
65 -- provided as input to produce the next random number, and updated so | |
66 -- that it is ready to produce the next one. | |
67 | |
68 type State is private; | |
69 -- A non-limited version of a Generator's internal state | |
70 | |
71 function Random (Gen : Generator) return Float; | |
72 function Random (Gen : Generator) return Long_Float; | |
73 -- Return pseudo-random numbers uniformly distributed on [0.0 .. 1.0) | |
74 | |
75 function Random (Gen : Generator) return Interfaces.Unsigned_32; | |
76 function Random (Gen : Generator) return Interfaces.Unsigned_64; | |
77 -- Return pseudo-random numbers uniformly distributed on T'First .. T'Last | |
78 -- for builtin integer types. | |
79 | |
80 generic | |
81 type Result_Subtype is (<>); | |
82 Default_Min : Result_Subtype := Result_Subtype'Val (0); | |
83 function Random_Discrete | |
84 (Gen : Generator; | |
85 Min : Result_Subtype := Default_Min; | |
86 Max : Result_Subtype := Result_Subtype'Last) return Result_Subtype; | |
87 -- Returns pseudo-random numbers uniformly distributed on Min .. Max | |
88 | |
89 generic | |
90 type Result_Subtype is digits <>; | |
91 function Random_Float (Gen : Generator) return Result_Subtype; | |
92 -- Returns pseudo-random numbers uniformly distributed on [0 .. 1) | |
93 | |
94 type Initialization_Vector is | |
95 array (Integer range <>) of Interfaces.Unsigned_32; | |
96 -- Provides the most general initialization values for a generator (used | |
97 -- in Reset). In general, there is little point in providing more than | |
98 -- a certain number of values (currently 624). | |
99 | |
100 procedure Reset (Gen : Generator); | |
101 -- Re-initialize the state of Gen from the time of day | |
102 | |
103 procedure Reset (Gen : Generator; Initiator : Initialization_Vector); | |
104 procedure Reset (Gen : Generator; Initiator : Interfaces.Integer_32); | |
105 procedure Reset (Gen : Generator; Initiator : Interfaces.Unsigned_32); | |
106 procedure Reset (Gen : Generator; Initiator : Integer); | |
107 -- Re-initialize Gen based on the Initiator in various ways. Identical | |
108 -- values of Initiator cause identical sequences of values. | |
109 | |
110 procedure Reset (Gen : Generator; From_State : Generator); | |
111 -- Causes the state of Gen to be identical to that of From_State; Gen | |
112 -- and From_State will produce identical sequences of values subsequently. | |
113 | |
114 procedure Reset (Gen : Generator; From_State : State); | |
115 procedure Save (Gen : Generator; To_State : out State); | |
116 -- The sequence | |
117 -- Save (Gen2, S); Reset (Gen1, S) | |
118 -- has the same effect as Reset (Gen2, Gen1). | |
119 | |
120 procedure Reset (Gen : Generator; From_Image : String); | |
121 function Image (Gen : Generator) return String; | |
122 -- The call | |
123 -- Reset (Gen2, Image (Gen1)) | |
124 -- has the same effect as Reset (Gen2, Gen1); | |
125 | |
126 Max_Image_Width : constant := 11 * 624; | |
127 -- Maximum possible length of result of Image (...) | |
128 | |
129 function Image (Of_State : State) return String; | |
130 -- A String representation of Of_State. Identical to the result of | |
131 -- Image (Gen), if Of_State has been set with Save (Gen, Of_State). | |
132 | |
133 function Value (Coded_State : String) return State; | |
134 -- Inverse of Image on States | |
135 | |
136 private | |
137 | |
138 N : constant := 624; | |
139 -- The number of 32-bit integers in the shift register | |
140 | |
141 M : constant := 397; | |
142 -- Feedback distance from the current position | |
143 | |
144 subtype State_Val is Interfaces.Unsigned_32; | |
145 type State is array (0 .. N - 1) of State_Val; | |
146 | |
147 type Writable_Access (Self : access Generator) is limited null record; | |
148 -- Auxiliary type to make Generator a self-referential type | |
149 | |
150 type Generator is limited record | |
151 Writable : Writable_Access (Generator'Access); | |
152 -- This self reference allows functions to modify Generator arguments | |
153 | |
154 S : State := (others => 0); | |
155 -- The shift register, a circular buffer | |
156 | |
157 I : Integer := N; | |
158 -- Current starting position in shift register S (N means uninitialized) | |
159 -- We should avoid using the identifier I here ??? | |
160 end record; | |
161 | |
162 end System.Random_Numbers; |