FastPermute(3) User Contributed Perl Documentation FastPermute(3)NAMEAlgorithm::FastPermute - Rapid generation of permutations
SYNOPSIS
use Algorithm::FastPermute ('permute');
my @array = (1..shift());
permute {
print "@array\n"; # Print all the permutations
} @array;
DESCRIPTIONAlgorithm::FastPermute generates all the permutations of an array. You
pass a block of code, which will be executed for each permutation. The
array will be changed in place, and then changed back again before
"permute" returns. During the execution of the callback, the array is
read-only and you'll get an error if you try to change its length. (You
can change its elements, but the consequences are liable to confuse you
and may change in future versions.)
You have to pass an array, it can't just be a list. It does work with
special arrays and tied arrays, though unless you're doing something
particularly abstruse you'd be better off copying the elements into a
normal array first.
It's very fast. My tests suggest it's four or five times as fast as
Algorithm::Permute's traditional interface. If you're permuting a
large list (nine or more elements, say) then you'll appreciate this
enormously. If your lists are short then Algorithm::Permute will still
finish faster than you can blink, and you may find its interface more
convenient.
In fact, the FastPermute interface (and code) is now also included in
Algorithm::Permute, so you may not need both. Enhancements and bug
fixes will appear here first, from where (at Edwin Pratomo's
discretion) they'll probably make their way into Algorithm::Permute.
The code is run inside a pseudo block, rather than as a normal
subroutine. That means you can't use "return", and you can't jump out
of it using "goto" and so on. Also, "caller" won't tell you anything
helpful from inside the callback. Such is the price of speed.
The order in which the permutations are generated is not guaranteed, so
don't rely on it.
EXPORT
The "permute" function is exported by default.
AUTHOR
Robin Houston, <robin@kitsite.com>
Based on a C program by Matt Day.
SEE ALSO
Algorithm::Permute
COPYRIGHT
Copyright (c) 2001-2008, Robin Houston. All Rights Reserved. This
module is free software. It may be used, redistributed and/or modified
under the same terms as Perl itself.
perl v5.14.0 2008-02-23 FastPermute(3)