Tree::Simple::Visitor::PreOrderTraversal - A Visitor for pre-order traversal a Tree::Simple hierarchy


  use Tree::Simple::Visitor::PreOrderTraversal;

  # create an visitor
  my $visitor = Tree::Simple::Visitor::PreOrderTraversal->new();

  # pass our visitor to the tree

  # print our results
  print join ", " => $visitor->getResults();

  # this will print this:
  #   1 1.1 1.1.1 1.2 2 2.1 3 3.1
  # assuming your tree is like this:
  #   1
  #     1.1
  #       1.1.1
  #     1.2
  #   2
  #     2.1
  #   3
  #     3.1


Pre-order traversal is a depth-first traversal method in which the sub-tree's are processed after the parent. It is essentially a wrapper around the base Tree::Simple::Visitor class, and is a separate module here for completeness. (If you have a post-order, you should have a pre-order too).



There are no arguments to the constructor the object will be in its default state. You can use the setNodeFilter method to customize its behavior.

includeTrunk ($boolean)

Based upon the value of $boolean, this will tell the visitor to include the trunk of the tree in the traversal as well.

setNodeFilter ($filter_function)

This method accepts a CODE reference as its $filter_function argument and throws an exception if it is not a code reference. This code reference is used to filter the tree nodes as they are collected. This can be used to customize output, or to gather specific information from a more complex tree node. The filter function should accept a single argument, which is the current Tree::Simple object.

visit ($tree)

This is the method that is used by Tree::Simple's accept method. It can also be used on its own, it requires the $tree argument to be a Tree::Simple object (or derived from a Tree::Simple object), and will throw and exception otherwise.


This method returns the accumulated results of the application of the node filter to the tree.



Bugs should be reported via the CPAN bug tracker at


See the CODE COVERAGE section in Tree::Simple::VisitorFactory for more information.


These Visitor classes are all subclasses of Tree::Simple::Visitor, which can be found in the Tree::Simple module, you should refer to that module for more information.


stevan little, <>


Copyright 2004, 2005 by Infinity Interactive, Inc.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.