Hash::MoreUtils(3)

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.

If no "LIST" is given, all keys are assumed as "LIST".

  "slice_def" HASHREF[, LIST]
As "slice", but only includes keys whose values are defined.

If no "LIST" is given, all keys are assumed as "LIST".

  "slice_exists" HASHREF[, LIST]
As "slice" but only includes keys which exist in the hashref.

If no "LIST" is given, all keys are assumed as "LIST".

  "slice_grep" BLOCK, HASHREF[, LIST]
As "slice", with an arbitrary condition.

If no "LIST" is given, all keys are assumed as "LIST".

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.

  "slice_map" HASHREF[, MAP]
Returns a hash containing the (key, value) pair for every key in "MAP".

If no "MAP" is given, all keys of "HASHREF" are assumed mapped to theirself.

  "slice_def_map" HASHREF[, MAP]
As "slice_map", but only includes keys whose values are defined.

If no "MAP" is given, all keys of "HASHREF" are assumed mapped to theirself.

  "slice_exists_map" HASHREF[, MAP]
As "slice_map" but only includes keys which exist in the hashref.

If no "MAP" is given, all keys of "HASHREF" are assumed mapped to theirself.

  "slice_grep_map" BLOCK, HASHREF[, MAP]
As "slice_map", with an arbitrary condition.

If no "MAP" is given, all keys of "HASHREF" are assumed mapped to theirself.

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:

•   RT: CPAN's request tracker

    <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Hash-MoreUtils>

•   AnnoCPAN: Annotated CPAN documentation

    <http://annocpan.org/dist/Hash-MoreUtils>

•   CPAN Ratings

    <http://cpanratings.perl.org/d/Hash-MoreUtils>

•   Search CPAN

    <http://search.cpan.org/dist/Hash-MoreUtils/>

ACKNOWLEDGEMENTS

COPYRIGHT & LICENSE
Copyright 2005 Hans Dieter Pearcey, all rights reserved. Copyright 2010-2013 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.