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RE: sort order of hash keys

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From:
Wagner-David
Date:
February 26, 2002 08:41
Subject:
RE: sort order of hash keys
Message ID:
113A7A0D1F47D511B92E00D0B7E03DAB0187BB80@pmail02.vikingfreight.com
	When you say, you can't use the sort routine directly, waht do you mean? You can sort the keys  in every color of the rainbow if necessary. Are you after the way they were inputted or do you have a sort sequence that you are really after?

Wags ;)

-----Original Message-----
From: maasha@image.dk [mailto:maasha@image.dk]
Sent: Tuesday, February 26, 2002 03:37
To: beginners@perl.org
Subject: Re: sort order of hash keys


yeah, i new this was tricky.

my hash keys / values have uneven names so i cant use a sort routine directly. thats why i would like to get the key / values in the same order as they are in the hashtable file.

whats the name of that hash modules?

:o)

martin


On Tue, Feb 26, 2002 at 10:28:16AM -0000, John Edwards wrote:
> hash keys are stored unsorted. If you have the following hash
> 
> %test = (	one => 1,
> 		two => 2,
> 		three => 3);
> 
> and print out the hash key/value pairs.
> 
> foreach $key (keys %test) {
> 	print "$key is $test{$key}\n";
> }
> 
> you will find they don't come out in the same order as they were stored.
> 
> You can perform a sort on the keys to arrange them in order
> 
> foreach $key (sort keys %test) {
> 	print "$key is $test{$key}\n";
> }
> 
> or you can reverse the hash, making the values the keys, and sort on the new
> keys
> 
> %reversed = reverse %test;
> 
> foreach $key (keys %reversed) {
> 	print "$key is $reversed{$key}\n";
> }
> 
> In doing this though, you must be aware that you will lose any data that has
> identical values. For example
> 
> %test = (	one => 1,
> 		two => 2,
> 		three => 3,
> 		alpha => 1,
> 		beta => 2,
> 		gamma => 3);
> 
> %reversed = reverse %test;
> 
> foreach $key (keys %reversed) {
> 	print "$key is $reversed{$key}\n";
> }
> 
> will print out
> 
> 1 is one
> 2 is two
> 3 is three
> 
> There is probably another/better way of doing this using the comparison
> operator <=>, but I don't know it. There is also a module available that
> lets you store and retrieve hashes in a fixed order.
> -----Original Message-----
> From: maasha@image.dk [mailto:maasha@image.dk]
> Sent: 26 February 2002 09:16
> To: beginners@perl.org
> Subject: sort order of hash keys
> 
> 
> hi
> 
> 
> i would like to know if theres a smart way to unwind a hashtable so that
> the key / value pairs comes out in the same order as they are in the table.
> 
> :o)
> 
> martin
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