Perl sort

xesecre has asked for the wisdom of the Perl Monks concerning the following question:

I have a question for the Wise Perl Monks, thanks in advance. I am using map and sort to sort by 2 columns. The trouble I am having is, it does sort the first column but it will not sort by any other column when I change the number. The list has numbers to sort. This is delimited by tab. What am I doing wrong?

my @sorted = map {$_->[0]}
             sort { $a->[0] <=> $b->[0] ||
             sort { $a->[1] <=> $b->[1] }
             map {chomp;[$_,split(/\t/)]} <FILE>;
print OUT "$_\n" for @sorted;
[download]

Comment on Perl sort Download Code

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Re: Perl sort by Corion (Patriarch) on Apr 26, 2016 at 14:30 UTC
You are calling `sort` twice, which makes little sense. Also, your code does not even compile. Most likely you wanted something like: `my @sorted = map {$_->[0]} sort { $a->[0] <=> $b->[0] \|\| $a->[1] <=> $b->[1] } map {chomp;[$_,split(/\t/)]} <FILE>; print OUT "$_\n" for @sorted;` [download]	[reply] [d/l] [select]
Re: Perl sort by Laurent_R (Canon) on Apr 26, 2016 at 20:28 UTC
In addition to the error pointed by Corion, I don't think you are trying to sort with the right items in the array reference you are building. Assuming one line of your file contains something like: `12\t45` [download] your first map: `map {chomp;[$_,split(/\t/)]}` [download] will transform this line into: `["12\t45", 12, 45]` [download] With such data, comparing: `$a->[0] <=> $b->[0] \|\| $a->[1] <=> $b->[1]` [download] in your sort code block makes little sense. I would assume you probably want something like: `$a->[1] <=> $b->[1] or $a->[2] <=> $b->[2]` [download]	[reply] [d/l] [select]