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TSort
cdesc-TSort.yaml
--- !ruby/object:RI::ClassDescription attributes: [] class_methods: [] comment: - !ruby/struct:SM::Flow::P body: TSort implements topological sorting using Tarjan's algorithm for strongly connected components. - !ruby/struct:SM::Flow::P body: TSort is designed to be able to be used with any object which can be interpreted as a directed graph. - !ruby/struct:SM::Flow::P body: TSort requires two methods to interpret an object as a graph, tsort_each_node and tsort_each_child. - !ruby/object:SM::Flow::LIST contents: - !ruby/struct:SM::Flow::LI label: "*" body: tsort_each_node is used to iterate for all nodes over a graph. - !ruby/struct:SM::Flow::LI label: "*" body: tsort_each_child is used to iterate for child nodes of a given node. type: :BULLET - !ruby/struct:SM::Flow::P body: The equality of nodes are defined by eql? and hash since TSort uses Hash internally. - !ruby/struct:SM::Flow::H level: 2 text: A Simple Example - !ruby/struct:SM::Flow::P body: "The following example demonstrates how to mix the TSort module into an existing class (in this case, Hash). Here, we're treating each key in the hash as a node in the graph, and so we simply alias the required #tsort_each_node method to Hash's #each_key method. For each key in the hash, the associated value is an array of the node's child nodes. This choice in turn leads to our implementation of the required #tsort_each_child method, which fetches the array of child nodes and then iterates over that array using the user-supplied block." - !ruby/struct:SM::Flow::VERB body: " require 'tsort'\n\n class Hash\n include TSort\n alias tsort_each_node each_key\n def tsort_each_child(node, &block)\n fetch(node).each(&block)\n end\n end\n\n {1=>[2, 3], 2=>[3], 3=>[], 4=>[]}.tsort\n #=> [3, 2, 1, 4]\n\n {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}.strongly_connected_components\n #=> [[4], [2, 3], [1]]\n" - !ruby/struct:SM::Flow::H level: 2 text: A More Realistic Example - !ruby/struct:SM::Flow::P body: "A very simple `make' like tool can be implemented as follows:" - !ruby/struct:SM::Flow::VERB body: " require 'tsort'\n\n class Make\n def initialize\n @dep = {}\n @dep.default = []\n end\n\n def rule(outputs, inputs=[], &block)\n triple = [outputs, inputs, block]\n outputs.each {|f| @dep[f] = [triple]}\n @dep[triple] = inputs\n end\n\n def build(target)\n each_strongly_connected_component_from(target) {|ns|\n if ns.length != 1\n fs = ns.delete_if {|n| Array === n}\n raise TSort::Cyclic.new("cyclic dependencies: #{fs.join ', '}")\n end\n n = ns.first\n if Array === n\n outputs, inputs, block = n\n inputs_time = inputs.map {|f| File.mtime f}.max\n begin\n outputs_time = outputs.map {|f| File.mtime f}.min\n rescue Errno::ENOENT\n outputs_time = nil\n end\n if outputs_time == nil ||\n inputs_time != nil && outputs_time <= inputs_time\n sleep 1 if inputs_time != nil && inputs_time.to_i == Time.now.to_i\n block.call\n end\n end\n }\n end\n\n def tsort_each_child(node, &block)\n @dep[node].each(&block)\n end\n include TSort\n end\n\n def command(arg)\n print arg, "\\n"\n system arg\n end\n\n m = Make.new\n m.rule(%w[t1]) { command 'date > t1' }\n m.rule(%w[t2]) { command 'date > t2' }\n m.rule(%w[t3]) { command 'date > t3' }\n m.rule(%w[t4], %w[t1 t3]) { command 'cat t1 t3 > t4' }\n m.rule(%w[t5], %w[t4 t2]) { command 'cat t4 t2 > t5' }\n m.build('t5')\n" - !ruby/struct:SM::Flow::H level: 2 text: Bugs - !ruby/object:SM::Flow::LIST contents: - !ruby/struct:SM::Flow::LI label: "*" body: "'tsort.rb' is wrong name because this library uses Tarjan's algorithm for strongly connected components. Although 'strongly_connected_components.rb' is correct but too long." type: :BULLET - !ruby/struct:SM::Flow::H level: 2 text: References - !ruby/object:SM::Flow::LIST contents: - !ruby/struct:SM::Flow::LI label: R. body: E. Tarjan, "Depth First Search and Linear Graph Algorithms", type: :UPPERALPHA - !ruby/struct:SM::Flow::P body: <em>SIAM Journal on Computing</em>, Vol. 1, No. 2, pp. 146-160, June 1972. constants: [] full_name: TSort includes: [] instance_methods: - !ruby/object:RI::MethodSummary name: each_strongly_connected_component - !ruby/object:RI::MethodSummary name: each_strongly_connected_component_from - !ruby/object:RI::MethodSummary name: strongly_connected_components - !ruby/object:RI::MethodSummary name: tsort - !ruby/object:RI::MethodSummary name: tsort_each - !ruby/object:RI::MethodSummary name: tsort_each_child - !ruby/object:RI::MethodSummary name: tsort_each_node name: TSort superclass:
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