162 lines
7.5 KiB
Ada
162 lines
7.5 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- G N A T . R A N D O M _ N U M B E R S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 2007-2015, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- Extended pseudo-random number generation
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-- This package provides a type representing pseudo-random number generators,
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-- and subprograms to extract various distributions of numbers from them. It
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-- also provides types for representing initialization values and snapshots of
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-- internal generator state, which permit reproducible pseudo-random streams.
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-- The generator currently provided by this package has an extremely long
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-- period (at least 2**19937-1), and passes the Big Crush test suite, with the
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-- exception of the two linear complexity tests. Therefore, it is suitable for
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-- simulations, but should not be used as a cryptographic pseudo-random source
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-- without additional processing.
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-- The design of this package effects is simplified compared to the design
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-- of standard Ada.Numerics packages. There is no separate State type; the
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-- Generator type itself suffices for this purpose. The parameter modes on
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-- Reset procedures better reflect the effect of these routines.
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-- Note: this package is marked SPARK_Mode Off, because functions Random work
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-- by side-effect to change the value of the generator, hence they should not
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-- be called from SPARK code.
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with System.Random_Numbers;
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with Interfaces; use Interfaces;
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package GNAT.Random_Numbers with
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SPARK_Mode => Off
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is
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type Generator is limited private;
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subtype Initialization_Vector is
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System.Random_Numbers.Initialization_Vector;
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function Random (Gen : Generator) return Float;
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function Random (Gen : Generator) return Long_Float;
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-- Return pseudo-random numbers uniformly distributed on [0 .. 1)
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function Random (Gen : Generator) return Interfaces.Integer_32;
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function Random (Gen : Generator) return Interfaces.Unsigned_32;
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function Random (Gen : Generator) return Interfaces.Integer_64;
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function Random (Gen : Generator) return Interfaces.Unsigned_64;
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function Random (Gen : Generator) return Integer;
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function Random (Gen : Generator) return Long_Integer;
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-- Return pseudo-random numbers uniformly distributed on T'First .. T'Last
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-- for various builtin integer types.
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generic
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type Result_Subtype is (<>);
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Default_Min : Result_Subtype := Result_Subtype'Val (0);
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function Random_Discrete
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(Gen : Generator;
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Min : Result_Subtype := Default_Min;
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Max : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
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-- Returns pseudo-random numbers uniformly distributed on Min .. Max
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generic
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type Result_Subtype is delta <>;
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Default_Min : Result_Subtype := 0.0;
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function Random_Ordinary_Fixed
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(Gen : Generator;
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Min : Result_Subtype := Default_Min;
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Max : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
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-- Returns pseudo-random numbers uniformly distributed on Min .. Max
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generic
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type Result_Subtype is delta <> digits <>;
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Default_Min : Result_Subtype := 0.0;
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function Random_Decimal_Fixed
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(Gen : Generator;
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Min : Result_Subtype := Default_Min;
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Max : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
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-- Returns pseudo-random numbers uniformly distributed on Min .. Max
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generic
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type Result_Subtype is digits <>;
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function Random_Float (Gen : Generator) return Result_Subtype;
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-- Returns pseudo-random numbers uniformly distributed on [0.0 .. 1.0)
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function Random_Gaussian (Gen : Generator) return Long_Float;
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function Random_Gaussian (Gen : Generator) return Float;
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-- Returns pseudo-random numbers normally distributed value with mean 0
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-- and standard deviation 1.0.
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procedure Reset (Gen : out Generator);
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-- Re-initialize the state of Gen from the time of day
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procedure Reset
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(Gen : out Generator;
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Initiator : Initialization_Vector);
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procedure Reset
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(Gen : out Generator;
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Initiator : Interfaces.Integer_32);
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procedure Reset
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(Gen : out Generator;
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Initiator : Interfaces.Unsigned_32);
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procedure Reset
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(Gen : out Generator;
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Initiator : Integer);
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-- Re-initialize Gen based on the Initiator in various ways. Identical
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-- values of Initiator cause identical sequences of values.
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procedure Reset (Gen : out Generator; From_State : Generator);
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-- Causes the state of Gen to be identical to that of From_State; Gen
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-- and From_State will produce identical sequences of values subsequently.
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procedure Reset (Gen : out Generator; From_Image : String);
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function Image (Gen : Generator) return String;
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-- The call
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-- Reset (Gen2, Image (Gen1))
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-- has the same effect as Reset (Gen2, Gen1);
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Max_Image_Width : constant :=
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System.Random_Numbers.Max_Image_Width + 2 + 20 + 5;
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-- Maximum possible length of result of Image (...)
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private
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type Generator is limited record
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Rep : System.Random_Numbers.Generator;
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Have_Gaussian : Boolean;
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-- The algorithm used for Random_Gaussian produces deviates in
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-- pairs. Have_Gaussian is true iff Random_Gaussian has returned one
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-- member of the pair and Next_Gaussian contains the other.
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Next_Gaussian : Long_Float;
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-- Next random deviate to be produced by Random_Gaussian, if
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-- Have_Gaussian.
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end record;
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end GNAT.Random_Numbers;
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