1Algorithm::Dependency::UWseeirghCto(n3t)ributed Perl DocAulmgeonrtiatthimo:n:Dependency::Weight(3)
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6 Algorithm::Dependency::Weight - Calculate dependency 'weights'
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9 version 1.112
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12 # Create a source from a file
13 my $Source = Algorithm::Dependency::Source->new( 'file.txt' );
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15 # Create a Weight algorithm object
16 my $alg = Algorithm::Dependency::Weight->new( source => $Source );
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18 # Find the weight for a single item
19 my $weight = $alg->weight('foo');
20 print "The weight of 'foo' is $weight\n";
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22 # Or a group
23 my $hash = $alg->weight_hash('foo', 'bar', 'baz');
24 print "The weight of 'foo', 'bar', and 'bar' are $hash->{foo},"
25 . " $hash->{bar} and $hash->{baz} respectively\n";
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27 # Or all of the items
28 my $all = $alg->weight_all;
29 print "The following is a list from heaviest to lightest:\n";
30 foreach ( sort { $all->{$b} <=> $all->{$a} } keys %$all ) {
31 print "$_: $all->{$_}\n";
32 }
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35 In dependency systems, it can often be very useful to calculate an
36 aggregate or sum for one or all items. For example, to find the "naive
37 install weight" of a Perl distribution (where "naive" means you treat
38 each distribution equally), you would want the distribution (1) + all
39 its dependencies (n) + all their dependencies (n2) recursively
40 downwards.
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42 If calculated using a normal Algorithm::Dependency object, the result
43 would be (in a simple systems) equal to:
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45 # Create your normal (non-ordered alg:dep)
46 my $dependency = Algorithm::Dependency->new( ... );
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48 # Find the naive weight for an item
49 my $weight = scalar($dependency->schedule('itemname'));
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51 "Algorithm::Dependency::Weight" provides a way of doing this with a
52 little more sophistication, and in a way that should work reasonable
53 well across all the Algorithm::Dependency family.
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55 Please note that the this might be a little (or more than a little)
56 slower than it could be for the limited case of generating weights for
57 all of the items at once in a dependency system with no selected items
58 and no circular dependencies. BUT you can at least rely on this class
59 to do the job properly regardless of the particulars of the situation,
60 which is probably more important.
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62 METHODS
63 new @params
64 The "new" constructor creates a new "Algorithm::Dependency::Weight"
65 object. It takes a number of key/value pairs as parameters (although at
66 the present time only one).
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68 source => $Source
69 The "source" param is mostly the same as for Algorithm::Dependency.
70 The one addition is that as a source you can provide an
71 Algorithm::Dependency object, and the Algorithm::Dependency::Source
72 for that will be used.
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74 Returns a new "Algorithm::Dependency::Weight" object, or "undef" on
75 error.
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77 source
78 The "source" accessor returns the source used for the weight
79 calculations.
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81 This will be either the one passed to the constructor, or the source
82 from inside the "Algorithm::Dependency" object passed as the "source"
83 param (not the object itself, its source).
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85 weight $name
86 The "weight" method takes the name of a single item and calculates its
87 weight based on the configuration of the
88 "Algorithm::Dependency::Weight" object.
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90 Returns the weight as a scalar (which in the naive case will be an
91 integer, but in more complex uses may be any real number), or "undef"
92 on error.
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94 weight_merged @names
95 The "weight_merged" method takes the name of a set of items and
96 calculates an aggregated weight for the whole set.
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98 Returns the weight as a scalar, or "undef" on error.
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100 weight_hash @names
101 The "weight_hash" method takes a list of item names, and calculates
102 their weights.
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104 Returns a reference to a "HASH" with the item names as keys and weights
105 as values, or "undef" on error.
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107 weight_all
108 The "weight_all" method provides the one-shot method for getting the
109 weights of all items at once. Please note that this does not do
110 anything different or special, but is slightly faster than iterating
111 yourself.
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113 Returns a reference to a "HASH" with the item names as keys and weights
114 as values, or "undef" on error.
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117 - Add support for non-naive weights via either custom code or method
118 name
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121 Algorithm::Dependency, Algorithm::Dependency::Source
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124 Bugs may be submitted through the RT bug tracker
125 <https://rt.cpan.org/Public/Dist/Display.html?Name=Algorithm-
126 Dependency> (or bug-Algorithm-Dependency@rt.cpan.org <mailto:bug-
127 Algorithm-Dependency@rt.cpan.org>).
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130 Adam Kennedy <adamk@cpan.org>
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133 This software is copyright (c) 2003 by Adam Kennedy.
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135 This is free software; you can redistribute it and/or modify it under
136 the same terms as the Perl 5 programming language system itself.
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140perl v5.36.0 2022-07-22 Algorithm::Dependency::Weight(3)