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Merged changes from the 1.5.2p2 release.

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Fred Drake 2000-04-03 20:13:55 +00:00
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34
Doc/lib/libwhrandom.tex
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@ -1,13 +1,27 @@
\section{\module{whrandom} ---
Floating point pseudo-random number generator.}
\declaremodule{standard}{whrandom}
Pseudo-random number generator}
\declaremodule{standard}{whrandom}
\modulesynopsis{Floating point pseudo-random number generator.}
This module implements a Wichmann-Hill pseudo-random number generator
class that is also named \code{whrandom}. Instances of the
\code{whrandom} class have the following methods:
class that is also named \class{whrandom}. Instances of the
\class{whrandom} class conform to the Random Number Generator
interface described in section \ref{rng-objects}. They also offer the
following method, specific to the Wichmann-Hill algorithm:
\begin{methoddesc}[whrandom]{seed}{\optional{x, y, z}}
Initializes the random number generator from the integers \var{x},
\var{y} and \var{z}. When the module is first imported, the random
number is initialized using values derived from the current time.
If \var{x}, \var{y}, and \var{z} are either omitted or \code{0}, the
seed will be computed from the current system time. If one or two
of the parameters are \code{0}, but not all three, the zero values
are replaced by ones. This causes some apparently different seeds
to be equal, with the corresponding result on the pseudo-random
series produced by the generator.
\end{methoddesc}
\begin{funcdesc}{choice}{seq}
Chooses a random element from the non-empty sequence \var{seq} and returns it.
@ -31,17 +45,23 @@ number is initialized using values derived from the current time.
Returns a random real number \var{N} such that \code{\var{a}<=\var{N}<\var{b}}.
\end{funcdesc}
When imported, the \code{whrandom} module also creates an instance of
the \code{whrandom} class, and makes the methods of that instance
When imported, the \module{whrandom} module also creates an instance of
the \class{whrandom} class, and makes the methods of that instance
available at the module level. Therefore one can write either
\code{N = whrandom.random()} or:
\begin{verbatim}
generator = whrandom.whrandom()
N = generator.random()
\end{verbatim}
Note that using separate instances of the generator leads to
independent sequences of pseudo-random numbers.
\begin{seealso}
\seemodule{random}{generators for various random distributions}
\seemodule{random}{Generators for various random distributions and
documentation for the Random Number Generator
interface.}
\seetext{Wichmann, B. A. \& Hill, I. D., ``Algorithm AS 183:
An efficient and portable pseudo-random number generator'',
\citetitle{Applied Statistics} 31 (1982) 188-190.}