Re: XML::Twig newbie question

[Anonymous Monk]

in reply to XML::Twig newbie question

What I can't figure out is, how to pass the name in $file to the event handler, or conversely, how to associate the found attribute back to the $file. I'm probably missing something obvious, but can't puzzle it out. Any suggestions would be greatly appreciated.

You're missing closures, examples in XML::Twig traversing tree and storing in an array, XML::Twig n00b, Tutorials: Closure on Closures

for my $file ( ... ){
    my $filename = $file;
    my %filnameKeyref;
    my $topicref = sub {
       ...
       $filenameKeyref{ $filename };
       return;
    };

    my $twig= XML::Twig->new(  ... => $topicref );
    $twig->...;
}

Although you ought to write that as

for my $file ( ... ){
    my $complexAssociations = FooAssoc( $file );
    WalkAndTalk( $complexAssociations );
}

[Jenda]

Another way would be to make the subroutine curried (that is expecting to get the parameters separately, not all at once):

foreach my $file (@files){
# set up the XML parser:
 my $twig= XML::Twig->new( 
  twig_handlers => { topicref => topicref_processing($file),
               xref => topicref_processing($file) },
 );
 $twig->parsefile($file);
 $twig->purge;
}

sub topicref_processing {
  my ($file) = @_;
  return sub {
    my($twig, $topicref) = @_;
    my($atts) = $topicref->atts();
    if($$atts{'keyref'}){
     ### associate this keyref with $file
    }
  }
}

[Anonymous Monk]

Another way would be to make the subroutine curried (that is expecting to get the parameters separately, not all at once):

Sure, you could write your closure that way ( the schönfinkeling way), but it gains you nothing in this example, it just takes a little more memory

[Jenda]

Depends on the complexity of the subroutine. Maybe you do not want to include all that code in the middle of the loop. I would not sweat over the tiny difference in memory footprint or the cost of two additional subroutine calls. Use whatever makes the code easier to maintain.

[slugger415]

"Curried?" sounds delicious! :-) Never heard that phrase before.

Thank you, this is a simple solution that works perfectly for me.

Scott

[Jenda]

If you are feeling adventurous, have a look at Wikipedia. Another place might be the comp.lang.functional FAQ or maybe Currying Schonfinkelling.

[slugger415]

Thank you for the suggestions; I will study the examples and try to understand them. A bit over my head at first sight.

Scott