NAME¶
Tree::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.