PERL Beginners

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iavian

2006-02-21, 3:55 am

Hi All

I got an 3 dimensional array , i want to sort them on 3 , 2 , 1st
dimension ..

Regards
Vijay

usenet@DavidFilmer.com

2006-02-21, 3:55 am

iavian wrote:
> Hi All
>
> I got an 3 dimensional array , i want to sort them on 3 , 2 , 1st dimension ..

Ah, my friend, what you want is the famous Schwartzian Transform (named
after Randal, of course).

See here: http://tinyurl.com/sx66o for links and references to this
technique.

--
http://DavidFilmer.com

usenet@DavidFilmer.com

2006-02-21, 3:55 am

use...@DavidFilmer.com wrote:
> Ah, my friend, what you want is the famous Schwartzian Transform

I should have mentioned - you need to be careful whether you're doing
numeric or alphabetic comparisons of the various indexes. For example:

print map { $_->[0] } #Randal Schwartz Rocks!!!
sort { $a->[3] <=> $b->[3] #numerically sort third index
|| $a->[2] <=> $b->[2] #numerically sort second index
|| $a->[1] cmp $b->[1] #alphabetic sort first index
} @array;

Be careful to note the difference between <=> and cmp and use whichever
is appropriate to your data.

--
http://DavidFilmer.com

Uri Guttman

2006-02-21, 3:55 am

>>>>> "u" == usenet <usenet@DavidFilmer.com> writes:

u> use...@DavidFilmer.com wrote:[color=darkred]

u> I should have mentioned - you need to be careful whether you're doing
u> numeric or alphabetic comparisons of the various indexes. For example:

u> print map { $_->[0] } #Randal Schwartz Rocks!!!
u> sort { $a->[3] <=> $b->[3] #numerically sort third index
u> || $a->[2] <=> $b->[2] #numerically sort second index
u> || $a->[1] cmp $b->[1] #alphabetic sort first index
u> } @array;

and to eliminate that key comparison confusion and speed things up if
you have large data sets, check out Sort::Maker on cpan. there is also
an article on it in the module and it can still be found on perl.com.

uri

--
Uri Guttman ------ uri@stemsystems.com -------- http://www.stemsystems.com
--Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
Search or Offer Perl Jobs ---------------------------- http://jobs.perl.org

iavian

2006-02-21, 3:55 am

, thanks buddy

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