SYNOPSIS

use Tree::Simple::Visitor::Sort;
# create a visitor object
my $visitor = Tree::Simple::Visitor::Sort->new();
$tree->accept($visitor);
# the tree is now sorted ascii-betically
# set the sort function to
# use a numeric comparison
$visitor->setSortFunction($visitor->NUMERIC);
$tree->accept($visitor);
# the tree is now sorted numerically
# set a custom sort function
$visitor->setSortFunction(sub {
my ($left, $right) = @_;
lc($left->getNodeValue()->{name}) cmp lc($right->getNodeValue()->{name});
});
$tree->accept($visitor);
# the tree's node are now sorted appropriately

DESCRIPTION

This implements a recursive multi-level sort of a Tree::Simple hierarchy. I think this deserves some more explanation, and the best way to do that is visually.

Given the tree:

    1
        1.3
        1.2
            1.2.2
            1.2.1
        1.1
    4
        4.1
    2
        2.1
    3
        3.3
        3.2
        3.1

A normal sort would produce the following tree:

    1
        1.1
        1.2
            1.2.1
            1.2.2
        1.3
    2
        2.1
    3
        3.1
        3.2
        3.3
    4
        4.1

A sort using the built-in REVERSE sort function would produce the following tree:

    4
        4.1
    3
        3.3
        3.2
        3.1
    2
        2.1
    1
        1.3
        1.2
            1.2.2
            1.2.1
        1.1

As you can see, no node is moved up or down from it's current depth, but sorted with it's siblings. Flexible customized sorting is possible within this framework, however, this cannot be used for tree-balancing or anything as complex as that.

METHODS

new

There are no arguments to the constructor the object will be in its default state. You can use the "setNodeFilter" and "setSortFunction" methods 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 sort as well.

setNodeFilter ($filter_function)

This method accepts a CODE reference as it's $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 sorted. This can be used 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.

setSortFunction ($sort_function)

This method accepts a CODE reference as it's $sort_function argument and throws an exception if it is not a code reference. The $sort_function is used by perl's builtin "sort" routine to sort each level of the tree. The $sort_function is passed two Tree::Simple objects, and must return 1 (greater than), 0 (equal to) or -1 (less than). The sort function will override and bypass any node filters which have been applied (see "setNodeFilter" method above), they cannot be used together.

Several pre-built sort functions are provided. All of these functions assume that calling "getNodeValue" on the Tree::Simple object will return a suitable sortable value.

REVERSE

This is the reverse of the normal sort using "cmp".

NUMERIC

This uses the numeric comparison operator "<=>" to sort.

REVERSE_NUMERIC

The reverse of the above.

ALPHABETICAL

This lowercases the node value before using "cmp" to sort. This results in a true alphabetical sorting.

REVERSE_ALPHABETICAL

The reverse of the above.

If you need to implement one of these sorting routines, but need special handling of your Tree::Simple objects (such as would be done with a node filter), I suggest you read the source code and copy and modify your own sort routine. If it is requested enough I will provide this feature in future versions, but for now I am not sure there is a large need.

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.

It should be noted that this is a destructive action, since the sort happens in place and does not produce a copy of the tree.

CODE COVERAGE

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

ACKNOWLEDGEMENTS

Thanks to Vitor Mori for the idea and much of the code for this Visitor.

AUTHORS

Vitor Mori, <[email protected]>

stevan little, <[email protected]>

COPYRIGHT AND LICENSE

Copyright 2004, 2005 by Vitor Mori & 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.