5.7. Retrieving from a Hash in Insertion Order5.7.1. ProblemThe keys and each functions traverse the hash elements in a strange order, and you want them in the order in which you inserted them. 5.7.2. Solutionuse Tie::IxHash; tie %HASH, "Tie::IxHash"; # manipulate %HASH @keys = keys %HASH; # @keys is in insertion order 5.7.3. DiscussionTie::IxHash makes keys, each, and values return the hash elements in the order they were added. This often removes the need to preprocess the hash keys with a complex sort comparison or maintain a distinct array containing the keys in the order they were inserted into the hash. Tie::IxHash also provides an object-oriented interface to splice, push, pop, shift, unshift, keys, values, and delete, among others. Here's an example, showing both keys and each: # initialize use Tie::IxHash; tie %food_color, "Tie::IxHash"; $food_color{"Banana"} = "Yellow"; $food_color{"Apple"} = "Green"; $food_color{"Lemon"} = "Yellow"; print "In insertion order, the foods are:\n"; foreach $food (keys %food_color) { print " $food\n"; } print "Still in insertion order, the foods' colors are:\n"; while (( $food, $color ) = each %food_color ) { print "$food is colored $color.\n"; } In insertion order, the foods are: Banana Apple Lemon Still in insertion order, the foods' colors are: Banana is colored Yellow. Apple is colored Green. Lemon is colored Yellow. 5.7.4. See AlsoThe documentation for the CPAN module Tie::IxHash; Recipe 13.5 Copyright © 2003 O'Reilly & Associates. All rights reserved. |
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