/ 
Hash-MoreUtils-0.02
River stage three • 11 direct dependents • 220 total dependents
/ Hash::MoreUtils

NAME

Hash::MoreUtils - Provide the stuff missing in Hash::Util

SYNOPSIS

use Hash::MoreUtils qw(slice slice_def slice_exists slice_grep
                       hashsort
                      );

DESCRIPTION

Similar to List::MoreUtils, Hash::MoreUtils contains trivial but commonly-used functionality for hashes.

FUNCTIONS

slice HASHREF[, LIST]

Returns a hash containing the (key, value) pair for every key in LIST.

slice_def HASHREF[, LIST]

As slice, but only includes keys whose values are defined.

slice_exists HASHREF[, LIST]

As slice but only includes keys which exist in the hashref.

slice_grep BLOCK, HASHREF[, LIST]

As slice, with an arbitrary condition.

Unlike grep, the condition is not given aliases to elements of anything. Instead, %_ is set to the contents of the hashref, to avoid accidentally auto-vivifying when checking keys or values. Also, 'uninitialized' warnings are turned off in the enclosing scope.

hashsort [BLOCK,] HASHREF

my @array_of_pairs  = hashsort \%hash;
my @pairs_by_length = hashsort sub { length($a) <=> length($b) }, \%hash;

Returns the (key, value) pairs of the hash, sorted by some property of the keys. By default (if no sort block given), sorts the keys with cmp.

I'm not convinced this is useful yet. If you can think of some way it could be more so, please let me know.

safe_reverse [BLOCK,] HASHREF

my %dup_rev = safe_reverse \%hash

sub croak_dup {
    my ($k, $v, $r) = @_;
    exists( $r->{$v} ) and
      croak "Cannot safe reverse: $v would be mapped to both $k and $r->{$v}";
    $v;
};
my %easy_rev = save_reverse \&croak_dup, \%hash

Returns safely reversed hash (value, key pairs of original hash). If no BLOCK is given, following routine will be used:

  sub merge_dup {
      my ($k, $v, $r) = @_;
      return exists( $r->{$v} )
             ? ( ref($r->{$v}) ? [ @{$r->{$v}}, $k ] : [ $r->{$v}, $k ] )
	     : $k;
  };

The BLOCK will be called with 3 arguments:

key

The key from the ( key, value ) pair in the original hash

value

The value from the ( key, value ) pair in the original hash

ref-hash

Reference to the reversed hash (read-only)

The BLOCK is expected to return the value which will used for the resulting hash.

AUTHOR

Hans Dieter Pearcey, <hdp@cpan.org> Jens Rehsack, <rehsack@cpan.org>

BUGS

Please report any bugs or feature requests to bug-hash-moreutils@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Hash-MoreUtils. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

perldoc Hash::MoreUtils

You can also look for information at:

ACKNOWLEDGEMENTS

COPYRIGHT & LICENSE

Copyright 2005 Hans Dieter Pearcey, all rights reserved. Copyright 2010 Jens Rehsack

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.