package Math::Random::OO;
use 5.006;
use strict;
use warnings;
our $VERSION = '0.21';
# Required modules
use Carp;
#--------------------------------------------------------------------------#
# main pod documentation
#--------------------------------------------------------------------------#
=head1 NAME
Math::Random::OO - Consistent object-oriented interface for generating random
numbers
=head1 SYNOPSIS
# Using factory functions
use Math::Random::OO qw( Uniform UniformInt );
push @prngs, Uniform(), UniformInt(1,6);
# Explicit creation of subclasses
use Math::Random::OO::Normal;
push @prngs, Math::Random::OO::Normal->new(0,2);
$_->seed(23) for (@prngs);
print( $_->next(), "\n") for (@prngs);
=head1 DESCRIPTION
CPAN contains many modules for generating random numbers in various ways
and from various probability distributions using pseudo-random number
generation algorithms or other entropy sources. (The L</"SEE ALSO"> section
has some examples.) Unfortunately, no standard interface exists across these
modules. This module defines an abstract interface for random number
generation. Subclasses of this model will implement specific types of random
number generators or will wrap existing random number generators.
This consistency will come at the cost of some efficiency, but will enable
generic routines to be written that can manipulate any provided random number
generator that adheres to the interface. E.g., a stochastic simulation could
take a number of user-supplied parameters, each of which is a Math::Random::OO
subclass object and which represent a stochastic variable with a particular
probability distribution.
=head1 USAGE
=cut
#--------------------------------------------------------------------------#
# import()
#--------------------------------------------------------------------------#
=head2 Factory Functions
use Math::Random::OO qw( Uniform UniformInt Normal Bootstrap );
$uniform = Uniform(-1,1);
$uni_int = UniformInt(1,6);
$normal = Normal(1,1);
$boot = Bootstrap( 2, 3, 3, 4, 4, 4, 5, 5, 5 );
In addition to defining the abstract interface for subclasses, this module
imports subclasses and exports factory functions upon request to simplify
creating many random number generators at once without typing
C<Math::Random::OO::Subclass-E<gt>new()> each time. The factory function names are
the same as the suffix of the subclass following C<Math::Random::OO>. When
called, they pass their arguments directly to the C<new> constructor method of
the corresponding subclass and return a new object of the subclass type.
Supported functions and their subclasses include:
=over
=item *
C<Uniform> -- L<Math::Random::OO::Uniform> (uniform distribution over a range)
=item *
C<UniformInt> -- L<Math::Random::OO::UniformInt> (uniform distribution of
integers over a range)
=item *
C<Normal> -- L<Math::Random::OO::Normal> (normal distribution with specified
mean and standard deviation)
=item *
C<Bootstrap> -- L<Math::Random::OO::Bootstrap> (bootstrap resampling from
a non-parameteric distribution)
=back
=cut
sub import {
my ($class, @symbols) = @_;
my $caller = caller;
for (@symbols) {
no strict 'refs';
my $subclass = "Math::Random::OO::$_";
eval "require $subclass";
*{"${caller}::$_"} =
eval "sub { return ${subclass}->new(\@_) }";
}
}
=head1 INTERFACE
All Math::Random::OO subclasses must follow a standard interface. They must
provide a C<new> method, a C<seed> method, and a C<next> method. Specific
details are left to each interface.
=cut
#--------------------------------------------------------------------------#
# new()
#--------------------------------------------------------------------------#
=head2 C<new>
This is the standard constructor. Each subclass will define parameters
specific to the subclass.
=cut
sub new {
my $class = shift;
return bless ({}, ref($class) ? ref($class) : $class);
}
#--------------------------------------------------------------------------#
# seed()
#--------------------------------------------------------------------------#
=head2 C<seed>
$prng->seed( @seeds );
This method takes seed (or list of seeds) and uses it to set the initial state
of the random number generator. As some subclasses may optionally use/require
a list of seeds, the interface mandates that a list must be acceptable.
Generators requiring a single seed must use the first value in the list.
As seeds may be passed to the built-in C<srand()> function, they may be
truncated as integers, so 0.12 and 0.34 would be the same seed.
=cut
sub seed { die "call to abstract method 'seed'" }
#--------------------------------------------------------------------------#
# rand()
#--------------------------------------------------------------------------#
=head2 C<next>
$rnd = $prng->next();
This method returns the next random number from the random number generator.
It does not take (and must not use) any parameters.
=cut
sub next { die "call to abstract method 'next'" }
1; #this line is important and will help the module return a true value
__END__
=head1 BUGS
Please report bugs using the CPAN Request Tracker at
http://rt.cpan.org/NoAuth/Bugs.html?Dist=Math-Random-OO
=head1 AUTHOR
David A Golden <dagolden@cpan.org>
http://dagolden.com/
=head1 COPYRIGHT
Copyright (c) 2004, 2005 by David A. Golden
This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.
The full text of the license can be found in the
LICENSE file included with this module.
=head1 SEE ALSO
This is not an exhaustive list -- search CPAN for that -- but represents some of
the more common or established random number generators that I've come across.
=over
=item L<Math::Random> -- multiple random number generators for different
distributions (a port of the C randlib)
=item L<Math::Rand48> -- perl bindings for the drand48 library (according to
perl56delta, this may already be the default after perl 5.005_52 if available)
=item L<Math::Random::MT> -- The Mersenne Twister PRNG (good and fast)
=item L<Math::TrulyRandom> -- an interface to random numbers from interrupt timing discrepancies
=back
=cut