in reply to Working With Arrays and Files

It looks to me like your problem is to first collect/organise the data you want, then to print it out. I recommend storing your lines in a hash, keyed off the last field on the line. I'll use a hash-of-lists-of-lists: 
  my %data = ();

  # get the data
  while (<TEMP>)
  {
    my @fields = split; # get fields
    my $key = pop @fields; # remove rightmost
    my $line = [@fields]; # $line is ref to list of fields

    push @{$data{$key}}, $line; # add to list of lines, in hash
  }
  close TEMP;

  #now print it:
  foreach my $key (sort keys %data);
  {
    print "$key\n";
    my @lines = @{$data{$key}}; # list of lines, from hash
    foreach my $line (@lines);
    {
      my @fields = @$line; # list of fields, from array-ref
      my $text = join(" ", @fields);
      print "$text\n";
    }
    print "\n";
  }

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Let me know if you can't follow the data-structure stuff. I've tried not to use any shortcuts, but I know it can be confusing at first. --Dave;

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Re: Re: Working With Arrays and Files
by kevinw (Novice) on Jul 23, 2002 at 20:16 UTC
    thanks for your help dave..... i'm still a lil unsure what this does 
    my $key = pop @fields; #is this the same as chomp?
my $line = [@fields];  

@$line #could you briefly explain the naming convension here?

    [download]
    and when i print it out, my columns are of different lengths, is there any way i can format it such that it comes out as straight columns? thanks again for your help....
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[d/l]
      OK,

      First, I create the @fields array, using the split function with default args (i.e. splits $_ into fields separated by whitespace).

      Then, I use the pop function to remove (and get) the rightmost element of the fields array. (push and pop manipulate the right hand side; shift and unshift manipulate the left). So after the $key has been popped, @fields is an array of all fields, except the rightmost.

      To push a list onto a list of arrays, I need an array reference. I could have used \@fields; but there are subtle ways that can go wrong when you're new to perl data-structures. So instead, I create a new anonymous array reference (using square brackets).

      Later, when I want convert the array-reference back into an array, I need to use the array dereferencing operator: @{$line}. I appologise for using a standard shorthand here: perl interprets @$line as @{$line}.

      Your last question is how to format you colmns more nicely. The easiest way (might work) is to join the elements of the array using a tab, instead of a space: 

          my $text = join("\t", @fields);

      [download]
      If this doesn't work, then there are many alternatives: you could define a format (see books); or you could write some clever padding functions; or you could store the original input text in the hash-of-lines; or you could get a CPAN module such as Data::ShowTable or Text::FormatTable. Personally, I usually don't bother: if I really need to view something as neat tables, then I use a table viewing application (or output as html). --Dave.
[reply]
[d/l]
[select]
        is there any way i can incorporate printf instead of the join?
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