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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- G N A T . R A N D O M _ N U M B E R S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2007, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- Extended pseudo-random number generation
-- This package provides a type representing pseudo-random number
-- generators, and subprograms to extract various distributions of numbers
-- from them. It also provides types for representing initialization values
-- and snapshots of internal generator state, which permit reproducible
-- pseudo-random streams.
-- The generator currently provided by this package has an extremely long
-- period (at least 2**19937-1), and passes the Big Crush test suite, with
-- the exception of the two linear complexity tests. Therefore, it is
-- suitable for simulations, but should not be used as a cryptographic
-- pseudo-random source without additional processing.
-- The design of this package effects some simplification from that of
-- the standard Ada.Numerics packages. There is no separate State type;
-- the Generator type itself suffices for this purpose. The parameter
-- modes on Reset procedures better reflect the effect of these routines.
with System.Random_Numbers;
with Interfaces; use Interfaces;
package GNAT.Random_Numbers is
type Generator is limited private;
subtype Initialization_Vector is
System.Random_Numbers.Initialization_Vector;
function Random (Gen : Generator) return Float;
function Random (Gen : Generator) return Long_Float;
-- Return pseudo-random numbers uniformly distributed on [0 .. 1)
function Random (Gen : Generator) return Interfaces.Integer_32;
function Random (Gen : Generator) return Interfaces.Unsigned_32;
function Random (Gen : Generator) return Interfaces.Integer_64;
function Random (Gen : Generator) return Interfaces.Unsigned_64;
function Random (Gen : Generator) return Integer;
function Random (Gen : Generator) return Long_Integer;
-- Return pseudo-random numbers uniformly distributed on T'First .. T'Last
-- for various builtin integer types.
generic
type Result_Subtype is (<>);
Default_Min : Result_Subtype := Result_Subtype'Val (0);
function Random_Discrete
(Gen : Generator;
Min : Result_Subtype := Default_Min;
Max : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
-- Returns pseudo-random numbers uniformly distributed on Min .. Max
generic
type Result_Subtype is digits <>;
function Random_Float (Gen : Generator) return Result_Subtype;
-- Returns pseudo-random numbers uniformly distributed on [0 .. 1)
function Random_Gaussian (Gen : Generator) return Long_Float;
function Random_Gaussian (Gen : Generator) return Float;
-- Returns pseudo-random numbers normally distributed value with mean 0
-- and standard deviation 1.0.
procedure Reset (Gen : out Generator);
-- Re-initialize the state of Gen from the time of day
procedure Reset
(Gen : out Generator;
Initiator : Initialization_Vector);
procedure Reset
(Gen : out Generator;
Initiator : Interfaces.Integer_32);
procedure Reset
(Gen : out Generator;
Initiator : Interfaces.Unsigned_32);
procedure Reset
(Gen : out Generator;
Initiator : Integer);
-- Re-initialize Gen based on the Initiator in various ways. Identical
-- values of Initiator cause identical sequences of values.
procedure Reset (Gen : out Generator; From_State : Generator);
-- Causes the state of Gen to be identical to that of From_State; Gen
-- and From_State will produce identical sequences of values subsequently.
procedure Reset (Gen : out Generator; From_Image : String);
function Image (Gen : Generator) return String;
-- The call
-- Reset (Gen2, Image (Gen1))
-- has the same effect as Reset (Gen2, Gen1);
Max_Image_Width : constant :=
System.Random_Numbers.Max_Image_Width + 2 + 20 + 5;
-- Maximum possible length of result of Image (...)
private
type Generator is limited record
Rep : System.Random_Numbers.Generator;
Have_Gaussian : Boolean;
-- The algorithm used for Random_Gaussian produces deviates in
-- pairs. Have_Gaussian is true iff Random_Gaussian has returned one
-- member of the pair and Next_Gaussian contains the other.
Next_Gaussian : Long_Float;
-- Next random deviate to be produced by Random_Gaussian, if
-- Have_Gaussian.
end record;
end GNAT.Random_Numbers;
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