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Re: A brief tutorial on Perl's native sorting facilities.

by teun-arno (Initiate)
on Nov 21, 2008 at 23:02 UTC ( #725251=note: print w/ replies, xml ) Need Help??


in reply to A brief tutorial on Perl's native sorting facilities.

This is a great tutorial. Special the code with Data::Dumper. This makes clear how map and sort interact. Just a minor. The code will not run as displayed. So I added a runnable example :

use Data::Dumper ## Build an array of anonymous arrays, ## each of which contains the sort field and the original element. @anons = map{ [ substr( $_, 1 ) , $_ ] } qw[ A473 B659 C123 D222 E0 +01 ];; my $dd=Data::Dumper->new([\@anons],[ qw(anons) ] )->Indent(2)->Quote +keys(0)->Dump; print $dd; print '-' x 40 , "\n"; ## Now sort the anonymous arrays ## by comparing the extracted fields. @sortedAnons = sort{ $a->[ 0 ] <=> $b->[ 0 ] } @anons;; my $dd=Data::Dumper->new([\@sortedAnons],[ qw(sortedAnons) ] )->Inde +nt(2)->Quotekeys(0)->Dump; print $dd; print '-' x 40 , "\n"; ## Finally, build the required sorted array ## by extracting the original elements discarding the sort fields. @sorted = map{ $_->[ 1 ] } @sortedAnons;; my $dd=Data::Dumper->new([\@sorted],[ qw(sorted) ] )->Indent(2)->Quo +tekeys(0)->Dump; print $dd; print '-' x 40 , "\n"; The above code will show : $anons = [ [ '473', 'A473' ], [ '659', 'B659' ], [ '123', 'C123' ], [ '222', 'D222' ], [ '001', 'E001' ] ]; ---------------------------------------- $sortedAnons = [ [ '001', 'E001' ], [ 123, 'C123' ], [ 222, 'D222' ], [ 473, 'A473' ], [ 659, 'B659' ] ]; ---------------------------------------- $sorted = [ 'E001', 'C123', 'D222', 'A473', 'B659', ]; ----------------------------------------


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