mapping and sorting array of files in perl

Question

I have this array of files which looks like this :

my @html_pages_files = ("html.17", "html.9", "html.0", "html.10");

I will put the extension of the file after the sort part. Basically the file name will be /html.\d/. The thing is I'm trying to sort it using map and sort function :

map { $_->[1] }
  sort { $a->[0] <=> $b->[0] }
     map { /html\.(.*)/; [$1, $_] }
        @html_pages_files;
print "@html_pages_files\n";

However the output remains the same as the original array. I've followed step by step @Chas. Owens answer here : Using Perl, how can I sort an array using the value of a number inside each array element?. Note that I'm pretty new to perl so I don't get all the details.

Does anybody seed where the error is ? Thank you!!!

For one, you're not checking to see if the regex match inside that map block succeeds. Right now if it doesn't match for some reason, you'll never know it and $1 will have the value from the previous regex match. I'd change it to /.../ or die if you expect that it will always pass. — Andy Lester
– Andy Lester, Commented Mar 7, 2013 at 16:58

ikegami · Accepted Answer · 2013-03-07 17:02:36Z

6

You never save the sorted results!

@html_pages_files =
   map { $_->[0] }
    sort { $a->[1] <=> $b->[1] }
     map { /html\.(.*)/; [$_, $1] }
      @html_pages_files;

(For consistency, I always put the whole string in the first element of the array.)

answered Mar 7, 2013 at 17:02

ikegami

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mob · Accepted Answer · 2013-03-07 16:59:47Z

4

Your sorting logic looks correct but you are not assigning the result of the operation to anything, so you are not changing @html_pages_files. Try

@html_pages_files = map {$_->[1] } 
                    sort {$a->[0] <=> $b->[0]} 
                    map {/html\.(.*)/; [$1, $_]} @html_pages_files;

answered Mar 7, 2013 at 16:59

mob

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2 Comments

Calvert42 Over a year ago

I've got it. actually you have to create a knew array in order to work, it looks like this : my @sorted = map{$_->[1]} sort{$a->[0] <=> $b->[0]} map{/html\.(.*)/; [$1, $_]} @html_pages_files; Nevertheless thank you for your advices!!!

ikegami Over a year ago

@user2007958, You can, but you don't have, as both of us have shown.

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