Perl Sort Array

Question

I am trying to figure out how to sort list of file names in Perl.

Each file is a PDF file that I am merging into a single pdf using Perl's PDF::Reuse

Each pdf file name has two unique identifier. 1) is the account ID & 2) report type.

Example:

C1234.lfs.pdf

C1234 = account id lfs = report type.

each account could have several reports that need to be in a specific order.

How can I specify the order of report types? I want to use a config file where the script would look to see what order to sort each accounts reports before merging to 1 pdf file. Order I would like is:

AcctId.lau.pdf AcctId.lsm.pdf AcctId.lad.pdf AcctId.lfs.pdf AcctId.lbe.pdf

@PDFS = (<*l*.pdf>);
@REVERSED_LIST = reverse(@PDFS);
prFile($OutPut);
for my $pdf (@REVERSED_LIST) {
    next if($pdf eq $OutPut);
    &Logit("Adding $pdf to $OutPut");
    prDoc($pdf);
}
prEnd();

Sorry if I am not explaining this correctly any help and suggestions are appreciated.

New code being tested not giving correct order.

@PDFS = (<*l*.pdf>);
my %lsfOrder = (lua=>0, lsm=>1, lfw=>2);
@SORTED = map { $_->[0] } # Take just the original file name
     sort { 
        $a->[1] cmp $b->[1] ? 
          $a->[1] cmp $b->[1] : # compare by account id if different
          $lsfOrder{$a->[2]} <=> $lsfOrder{$b->[2]} 
      }
      map {
        [ $_, split('.', $_) ] # split into id/type once at the beginning
      } @PDFS;

prFile($OutPut);
for my $pdf (@SORTED) {
   next if($pdf eq $OutPut);
   &Logit("Adding $pdf to $OutPut");
   #print "Adding $pdf to $OutPut\n";
       prDoc($pdf);
}
    prEnd();

JoshG79 · Accepted Answer · 2013-08-09 15:37:20Z

2

Perl sort takes a code block as its first argument that can control the sorting. There are two special variables defined, '$a', and '$b' which are two elements to compare. From there, you would use cmp and <=> to compare different parts of the strings and return whether a is less-than, greater-than or equal-to b. The sort function picks $a and $b based on its internal sorting algorithm from your list. E.g.:

@SORTED = sort {
  my @a = split ".", $a;
  my @b = split ".", $b;
  if ($a[0] cmp $b[0] != 0) { return $a[0] cmp $b[0] }
  my %lsfOrder = (lau=>0, lsm=>1, lad=>2, lfs=>3, lbe=>4);
  my $lsfA = $lsfOrder{$a[1]};
  my $lsfB = $lsfOrder{$b[1]};
  return $lsfA <=> $lsfB;
} @PDFS;

The code above splits the file names on the '.'. Then it compares the first element (the account id) and if they aren't the same, returns the result of that comparison. Otherwise it returns the result of comparing the report type. It converts the lsf into an integer in the order you've given, then compares those integers.

Edit: Joe Z has good suggestions for speed-ups. To summarize:

my %lsfOrder = (lau=>0, lsm=>1, lad=>2, lfs=>3, lbe=>4);
@SORTED = map { $_->[0] } # Take just the original file name
          sort { 
            $a->[1] cmp $b->[1] ? 
              $a->[1] cmp $b->[1] : # compare by account id if different
              $lsfOrder{$a->[2]} <=> $lsfOrder{$b->[2]} # otherwise, compare by report type in specific order
          }
          map {
            [ $_, split('.', $_) ] # split into id/type once at the beginning
          } @PDFS;

edited Aug 9, 2013 at 15:37

answered Aug 9, 2013 at 14:32

JoshG79

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6 Comments

Joe Z Over a year ago

While this approach works, I would suggest moving my %lsfOrder out of the sort { } block, as you're constructing that hash for every key comparison. Also, I realize you wrote my $lsfA ... and my $lsfB ... for algorithmic clarity, but again these carry an overhead. If you're sorting a large list, may just want to compare $lsfOrder{$a[1]} and $lsfOrder{$b[1]} directly. And finally, doing the split every time can also add up.

Joe Z Over a year ago

Combining my comments into a terse rewrite:

@SORTED = map { $_->[0] } sort { $a->[1] cmp $b->[1] ? $a->[1] cmp $b->[1] : $lsfOrder{$a->[2]} <=> $lsfOrder{$b->[2]} } map { [ $_, split('.', $_) ] } @PDFS;

user1279586 Over a year ago

Thanks guys, Unless I do a reverse sort on the @SORTED it is not giving me the correct order. 20130809:12:42:10 Adding c09968.lfw.pdf to test20130809-3.pdf 20130809:12:42:10 Adding c09968.lsm.pdf to test20130809-3.pdf 20130809:12:42:10 Adding c09968.lua.pdf to test20130809-3.pdf desired output would be lua.pdf lsm.pdf lfw.pdf. Thoughts?

JoshG79 Over a year ago

Note that 'lfw' is not in the lsfOrder hash. You should add this in the right spot (and any others you may have). Also, check that you have all the as and bs correct, since the code above should put "lua" before "lsm". And finally, you can reverse the sort by changing all the as to bs and bs to as in the sort block.

user1279586 Over a year ago

Right not I am working with only three reports so my lstOrder has is my %lsfOrder = (lau=>0, lsm=>1, lfw=>2); I will check the A&Bs

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