NAME¶
Algorithm::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.