NAME List::Uniq - extract the unique elements of a list SYNOPSIS use List::Uniq ':all'; @uniq = uniq(@list); $list = [ qw|foo bar baz foo| ]; $uniq = uniq($list); DESCRIPTION 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. FUNCTIONS uniq( { OPTIONS }, ele1, ele2, ..., eleN ) 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: * sort 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. * flatten If set to a true value, array references in the list will be recursively flattened, such that ( 'foo', [ [ 'bar' ] ], [ [ [ 'baz', 'quux' ] ] ] ) becomes ( 'foo', 'bar', 'baz', 'quux' ) flatten defaults to true. * compare 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. EXPORTS Nothing by default. Optionally the uniq function. Everything with the :all tag. SEE ALSO Array::Unique If you want to unique a list as you insert into it, see Array::Unique. "uniq" in List::Util "uniq" in PerlPowerTools AUTHOR James FitzGibbon CREDITS 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 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.