Algorithm::Dependency:UsergContributed Perl DoAlgorithm::Dependency::Weight(3)NAMEAlgorithm::Dependency::Weight - Calculate dependency 'weights'
SYNOPSIS
# 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";
}
DESCRIPTION
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.
METHODS
new @params
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 => $Source
The "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.
source
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).
weight $name
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.
weight_merged @names
The "weight_merged" method takes the name of a set of items and
calculates an aggregated weight for the whole set.
Returns the weight as a scalar, or "undef" on error.
weight_hash @names
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.
weight_all
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.
TO DO
- Add support for non-naive weights via either custom code or method
name
SUPPORT
Bugs should be submitted via the CPAN bug tracker, located at
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Algorithm-Dependency
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Algorithm-Dependency>
For general comments, contact the author.
AUTHOR
Adam Kennedy <adamk@cpan.org>
SEE ALSO
Algorithm::Dependency, Algorithm::Dependency::Source
COPYRIGHT
Copyright 2003 - 2009 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.
perl v5.14.1 2009-04-14 Algorithm::Dependency::Weight(3)
