NAME

Math::Counting - Combinatorial counting operations

VERSION

version 0.1304

SYNOPSIS

Academic

  use Math::Counting ':student';
  printf "Given n=%d, k=%d:\nF=%d\nP=%d\nC=%d\n",
    $n, $k, factorial($n), permutation($n, $k), combination($n, $k);

Engineering

  use Math::Counting ':big';
  printf "Given n=%d, k=%d, r=%d:\nF=%d\nP=%d\nD=%d\nC=%d\n",
    $n, $k, $r, bfact($n), bperm($n, $k, $r), bderange($n), bcomb($n, $k, $r);

DESCRIPTION

Compute the factorial, number of permutations and number of combinations.

The :big functions are wrappers around "bfac" in Math::BigInt with a bit of arithmetic between. Also the bperm function accepts an additional boolean to indicate repetition.

The student versions exist to illustrate the computation "in the raw" as it were. To see these computations in action, Use The Source, Luke.

FUNCTIONS

factorial

  $f = factorial($n);

Return the number of arrangements of n, notated as n!.

This function employs the algorithmically elegant "student" version using real arithmetic.

bfact

  $f = bfact($n);

Return the value of the function "bfac" in Math::BigInt, which is the "Right Way To Do It."

permutation

  $p = permutation($n, $k);

Return the number of arrangements, without repetition, of k elements drawn from a set of n elements, using the "student" version.

bperm

  $p = bperm($n, $k, $r);

Return the computations:

  n^k           # with repetition
  n! / (n-k)!   # without repetition

bderange()

"A derangement is a permutation in which none of the objects appear in their "natural" (i.e., ordered) place." -- wolfram under "SEE ALSO"

Return the computation:

  !n = n! * ( sum (-1)^k/k! for k=0 to n )

combination

  $c = combination($n, $k);

Return the number of ways to choose k elements from a set of n elements, without repetition.

This is algorithm expresses the "student" version.

bcomb

  $c = bcomb($n, $k, $r);

Return the combination computations:

  (n+k-1)! / k!(n-1)!   # with repetition
  n! / k!(n-k)!         # without repetition

TO DO

Allow specification of the math processor to use.

Provide the gamma function for the factorial of non-integer numbers?

SEE ALSO

"bfac" in Math::BigInt

Higher Order Perl by Mark Jason Dominus (http://hop.perl.plover.com).

Mastering Algorithms with Perl by Orwant, Hietaniemi & Macdonald (http://www.oreilly.com/catalog/maperl).

http://en.wikipedia.org/wiki/Factorial, http://en.wikipedia.org/wiki/Permutation & http://en.wikipedia.org/wiki/Combination

http://www.mathsisfun.com/combinatorics/combinations-permutations-calculator.html

http://mathworld.wolfram.com/Derangement.html

Naturally, there are a plethora of combinatorics packages available, take your pick:

Algorithm::Combinatorics, Algorithm::Loops, Algorithm::Permute, CM::Group::Sym, CM::Permutation, Games::Word, List::Permutor, Math::Combinatorics, Math::GSL::Permutation, Math::Permute::List, String::Glob::Permute, String::OrderedCombination

CREDITS

Special thanks to:

* Paul Evans

* Mike Pomraning

* Petar Kaleychev

* Dana Jacobsen

AUTHOR

Gene Boggs <gene@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2014 by Gene Boggs.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm Math::Counting

perl -MCPAN -e shell
install Math::Counting