List::Uniq - extract the unique elements of a list
use List::Uniq ':all';
@uniq = uniq(@list);
$list = [ qw|foo bar baz foo| ];
$uniq = uniq($list);
List::Uniq extracts the unique elements of a list. This is a commonly re-written (or at least re-looked-up) idiom in Perl programs.
uniq() takes a list of elements and returns the unique elements of the list. Each element may be a scalar value or a reference to a list.
If the first element is a hash reference it is taken to be a set of options that alter the way in which the unique filter is applied. The keys of the option set are:
If set to a true value, the unique elements of the list will be returned sorted. Perl's default sort will be used unless the compare option is also passed.
sort defaults to false.
If set to a true value, array references in the list will be recursively flattened, such that
( 'foo', [ [ 'bar' ] ], [ [ [ 'baz', 'quux' ] ] ] )
( 'foo', 'bar', 'baz', 'quux' )
flatten defaults to true.
A code reference that will be used to sort the elements of the list if the sort option is set. Passing a non-coderef will cause uniq to throw an exception.
The code ref will be passed a pair of list elements to be compared and should return the same values as the cmp operator.
Using a custom sort slows things down because the sort routine will be outside of the List::Uniq package. This requires that the pairs to be compared be passed as parameters to the sort routine, not set as package globals (see "sort" in perlfunc). If speed is a concern, you are better off sorting the return of uniq yourself.
The return value is a list of the unique elements if called in list context or a reference to a list of unique elements if called in scalar context.
Nothing by default.
Optionally the uniq function.
Everything with the :all tag.
If you want to unique a list as you insert into it, see Array::Unique by Gabor Szabo.
This module was written out of a need to unique an array that was auto-vivified and thus not easily tied to Array::Unique.
James FitzGibbon <email@example.com>
The idioms used to unique lists are taken from recipe 4.7 in the Perl Cookbook, 2e., published by O'Reilly and Associates and from the Perl FAQ section 5.4.
I pretty much just glued it together in a way that I find easy to use. Hopefully you do too.
Copyright (c) 2004-2008 Primus Telecommunications Canada Inc.
Copyright (c) 2008-2010 James FitzGibbon
All Rights Reserved.
This library is free software; you may use it under the same terms as perl itself.
To install List::Uniq, copy and paste the appropriate command in to your terminal.
perl -MCPAN -e shell
For more information on module installation, please visit the detailed CPAN module installation guide.