Algorithm::Dependency::Weight - Calculate dependency 'weights'
# Create a source from a file
my $Source = Algorithm::Dependency::Source->new( 'file.txt' );
# Create a Weight algorithm object
my $alg = Algorithm::Dependency::Weight->new( source => $Source );
# Find the weight for a single item
my $weight = $alg->weight('foo');
print "The weight of 'foo' is $weight\n";
# Or a group
my $hash = $alg->weight_hash('foo', 'bar', 'baz');
print "The weight of 'foo', 'bar', and 'bar' are $hash->{foo},"
. " $hash->{bar} and $hash->{baz} respectively\n";
# Or all of the items
my $all = $alg->weight_all;
print "The following is a list from heaviest to lightest:\n";
foreach ( sort { $all->{$b} <=> $all->{$a} } keys %$all ) {
print "$_: $all->{$_}\n";
}
In dependency systems, it can often be very useful to calculate an aggregate or sum for one or all items. For example, to find the "naive install weight" of a Perl distribution (where "naive" means you treat each distribution equally), you would want the distribtion (1) + all its dependencies (n) + all their dependencies (n2) recursively downwards.
If calculated using a normal Algorithm::Dependency object, the result would be (in a simple systems) equal to:
# Create your normal (non-ordered alg:dep)
my $dependency = Algorithm::Dependency->new( ... );
# Find the naive weight for an item
my $weight = scalar($dependency->schedule('itemname'));
Algorithm::Dependency::Weight provides a way of doing this
with a little more sophistication, and in a way that should work
reasonable well across all the Algorithm::Dependency family.
Please note that the this might be a little (or more than a little) slower than it could be for the limited case of generating weights for all of the items at once in a dependency system with no selected items and no circular dependencies. BUT you can at least rely on this class to do the job properly regardless of the particulars of the situation, which is probably more important.
The new constructor creates a new Algorithm::Dependency::Weight
object. It takes a number of key/value pairs as parameters (although
at the present time only one).
source param is mostly the same as for Algorithm::Dependency.
The one addition is that as a source you can provide an
Algorithm::Dependency object, and the Algorithm::Dependency::Source
for that will be used.
Returns a new Algorithm::Dependency::Weight object, or undef on error.
The source accessor returns the source used for the weight calculations.
This will be either the one passed to the constructor, or the source from
inside the Algorithm::Dependency object passed as the source param
(not the object itself, its source).
The weight method takes the name of a single item and calculates its
weight based on the configuration of the Algorithm::Dependency::Weight
object.
Returns the weight as a scalar (which in the naive case will be an
integer, but in more complex uses may be any real number), or undef
on error.
The weight_hash method takes a list of item names, and calculates
their weights.
Returns a reference to a HASH with the item names as keys and weights
as values, or undef on error.
The weight_all method provides the one-shot method for getting the
weights of all items at once. Please note that this does not do
anything different or special, but is slightly faster than iterating
yourself.
Returns a reference to a HASH with the item names as keys and weights
as values, or undef on error.
- Add support for non-naive weights via either custom code or method name
Bugs should be submitted via the CPAN bug tracker, located at
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Algorithm-Dependency
For general comments, contact the author.
Adam Kennedy <adamk@cpan.org>, http://ali.as/
Algorithm::Dependency, Algorithm::Dependency::Source
Copyright (c) 2003 - 2005 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this module.