Stevan Little > Tree-Binary-0.07 > Tree::Binary::Visitor::PostOrderTraversal

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Module Version: 0.05   Source   Latest Release: Tree-Binary-1.06

NAME ^

Tree::Binary::Visitor::PostOrderTraversal - Visitor object for Tree::Binary objects

SYNOPSIS ^

  use Tree::Binary;
  use Tree::Binary::Visitor::PostOrderTraversal;
  
  # create a visitor instance
  my $visitor = Tree::Binary::Visitor::PostOrderTraversal->new();                                                        
  
  # create a tree to visit 
  # this is an expression tree
  # representing ((2 + 2) * (4 + 5))
  my $btree = Tree::Binary->new("*")
                    ->setLeft(Tree::Binary->new("+")
                                ->setLeft(Tree::Binary->new("2"))
                                ->setRight(Tree::Binary->new("2")))
                    ->setRight(Tree::Binary->new("+")
                                ->setLeft(Tree::Binary->new("4"))
                                ->setRight(Tree::Binary->new("5")));

  # by default this will collect all the 
  # node values in depth-first order into 
  # our results 
  $tree->accept($visitor);        
  
  # get our results and print them
  print join ", ", $visitor->getResults();  # prints "2, 2, +, 4, 5, +, *" 
  
  # for more complex node objects, you can specify 
  # a node filter which will be used to extract the
  # information desired from each node
  $visitor->setNodeFilter(sub { 
                my ($t) = @_;
                return $t->getNodeValue()->description();
                });  

DESCRIPTION ^

Post-order traversal is a variation of the depth-first traversal in which the sub-tree's are processed before the parent. It is another alternative to Tree::Binary's traverse method which implements a depth-first, pre-order traversal.

METHODS ^

new

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.

getNodeFilter

This method returns the CODE reference set with setNodeFilter argument.

clearNodeFilter

This method clears node filter field.

setNodeFilter ($filter_function)

This method accepts a CODE reference as its $filter_function argument. 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::Binary object.

getResults

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

setResults

This method should not really be used outside of this class, as it just would not make any sense to. It is included in this class and in this documenation to facilitate subclassing of this class for your own needs. If you desire to clear the results, then you can simply call setResults with no argument.

visit ($tree)

The visit method accepts a Tree::Binary and applies the function set in new or setNodeFilter appropriately. The results of this application can be retrieved with getResults

BUGS ^

None that I am aware of. Of course, if you find a bug, let me know, and I will be sure to fix it.

CODE COVERAGE ^

See the CODE COVERAGE section of Tree::Binary for details.

AUTHOR ^

stevan little, <stevan@iinteractive.com>

COPYRIGHT AND LICENSE ^

Copyright 2004, 2005 by Infinity Interactive, Inc.

http://www.iinteractive.com

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

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