NAME

       Forest::Tree::Pure - An n-ary tree

SYNOPSIS

         use Forest::Tree;

         my $t = Forest::Tree::Pure->new(
             node     => 1,
             children => [
                 Forest::Tree::Pure->new(
                     node     => 1.1,
                     children => [
                         Forest::Tree::Pure->new(node => 1.1.1),
                         Forest::Tree::Pure->new(node => 1.1.2),
                         Forest::Tree::Pure->new(node => 1.1.3),
                     ]
                 ),
                 Forest::Tree::Pure->new(node => 1.2),
                 Forest::Tree::Pure->new(
                     node     => 1.3,
                     children => [
                         Forest::Tree::Pure->new(node => 1.3.1),
                         Forest::Tree::Pure->new(node => 1.3.2),
                     ]
                 ),
             ]
         );

         $t->traverse(sub {
             my $t = shift;
             print(('    ' x $t->depth) . ($t->node || '\undef') . "\n");
         });

DESCRIPTION

       This module is a base class for Forest::Tree providing functionality for immutable trees.

       It can be used independently for trees that require sharing of children between parents.

       There is no single authoritative parent (no upward links at all), and changing of data is
       not supported.

       This class is appropriate when many tree roots share the same children (e.g. in a
       versioned tree).

       This class is strictly a DAG, wheras Forest::Tree produces a graph with back references

ATTRIBUTES

       node
       children
           get_child_at ($index)
               Return the child at this position. (zero-base index)

           child_count
               Returns the number of children this tree has

       size
           size
           has_size
       height
           height
           has_height

METHODS

       is_leaf
           True if the current tree has no children

       traverse (\&func)
           Takes a reference to a subroutine and traverses the tree applying this subroutine to
           every descendant. (But not the root)

       visit (&func)
           Traverse the entire tree, including the root.

       fmap_cont (&func)
           A CPS form of "visit" that lets you control when and how data flows from the children.

           It takes a callback in the form:

               sub {
                   my ( $tree, $cont, @args ) = @_;

                   ...
               }

           and $cont is a code ref that when invoked will apply that same function to the
           children of $tree.

           This allows you to do things like computing the sum of all the node values in a tree,
           for instance:

               use List::Util qw(sum);

               my $sum = $tree->fmap_cont(sub {
                   my ( $tree, $cont ) = @_;

                   return sum( $tree->node, $cont->() );
               });

           And also allows one to stop traversal at a given point.

       add_children (@children)
       add_child ($child)
           Create a new tree node with the children appended.

           The children must inherit "Forest::Tree::Pure"

           Note that this method does not mutate the tree, instead it clones and returns a tree
           with the augmented list of children.

       insert_child_at ($index, $child)
           Insert a child at this position. (zero-base index)

           Returns a derived tree with overridden children.

       set_child_at ($index, $child)
           Replaces the child at $index with $child.

       remove_child_at ($index)
           Remove the child at this position. (zero-base index)

           Returns a derived tree with overridden children.

       locate (@path)
           Find a child using a path of child indexes. These two examples return the same object:

               $tree->get_child_at(0)->get_child_at(1)->get_child_at(0);

               $tree->locate(0, 1, 0);

       descend (@path)
           Like "lookup" except that it returns every object in the path, not just the leaf.

       "transform (\@path, $method, @args)"
           Performs a lookup on @path, applies the method $method with @args to the located node,
           and clones the path to the parent returning a derived tree.

           This method is also implemented in Forest::Tree by mutating the tree in place and
           returning the original tree, so the same transformations should work on both pure
           trees and mutable ones.

           This code:

               my $new = $root->transform([ 1, 3 ], insert_child_at => 3, $new_child);

           will locate the child at the path "[ 1, 3 ]", call "insert_child_at" on it, creating a
           new version of "[ 1, 3 ]", and then return a cloned version of "[ 1 ]" and the root
           node recursively, such that $new appears to be a mutated $root.

       set_node $new
           Returns a clone of the tree node with the node value changed.

       "replace $arg"
           Returns the argument. This is useful when used with "transform".

       clone
           Provided by MooseX::Clone.

           Deeply clones the entire tree.

           Subclasses should use MooseX::Clone traits to specify the correct cloning behavior for
           additional attributes if cloning is used.

       reconstruct_with_class $class
           Recursively recreates the tree by passing constructor arguments to $class.

           Does not use "clone".

       to_mutable_tree
           Invokes "reconstruct_with_class" with Forest::Tree as the argument.

       to_pure_tree
           Returns the invocant.

       get_child_index ($child)
           Returns the index of $child in "children" or undef if it isn't a child of the current
           tree.

BUGS

       All complex software has bugs lurking in it, and this module is no exception. If you find
       a bug please either email me, or add the bug to cpan-RT.

AUTHOR

       Yuval Kogman

COPYRIGHT AND LICENSE

       Copyright 2008-2014 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.