Tree::Simple::Visitor:UsertContributed Perl DocuTree::Simple::Visitor::Sort(3)NAMETree::Simple::Visitor::Sort - A Visitor for sorting a Tree::Simple
object heirarchy
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
heirarchy. I think this deserves some more explaination, 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.
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 in Tree::Simple::VisitorFactory for more
inforamtion.
SEE ALSO
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.
ACKNOWLEDGEMENTS
Thanks to Vitor Mori for the idea and much of the code for this
Visitor.
AUTHORS
Vitor Mori, <vvvv767@hotmail.com>
stevan little, <stevan@iinteractive.com>
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.
perl v5.14.1 2005-07-14 Tree::Simple::Visitor::Sort(3)
