From ed6231195b8c516a32019e1967366af7793e8313 Mon Sep 17 00:00:00 2001
From: akr <akr@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Thu, 17 Oct 2013 03:32:15 +0000
Subject: [PATCH] * lib/tsort.rb
 (TSort.each_strongly_connected_component_from):   Extracted from
 TSort#each_strongly_connected_component_from.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43326 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog          |  5 +++++
 NEWS               |  4 ++++
 lib/tsort.rb       | 28 +++++++++++++++++++++++++---
 test/test_tsort.rb | 10 ++++++++++
 4 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 40e11a5038..34044204f8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Oct 17 12:30:16 2013  Tanaka Akira  <akr@fsij.org>
+
+	* lib/tsort.rb (TSort.each_strongly_connected_component_from):
+	  Extracted from TSort#each_strongly_connected_component_from.
+
 Thu Oct 17 11:07:06 2013  Eric Hodel  <drbrain@segment7.net>
 
 	* lib/rubygems:  Update to RubyGems master 941c21a.  Changes:
diff --git a/NEWS b/NEWS
index 078c57c7c9..eb1af33c7a 100644
--- a/NEWS
+++ b/NEWS
@@ -244,6 +244,10 @@ with all sufficient information, see the ChangeLog file.
     inside the block, by default, unless the exception class is given
     explicitly.
 
+* TSort
+  * New methods:
+    * TSort.each_strongly_connected_component_from
+
 * WEBrick
   * The body of a response may now be a StringIO or other IO-like that responds
     to #readpartial and #read.
diff --git a/lib/tsort.rb b/lib/tsort.rb
index d0f3cd4caa..6061cd73fe 100644
--- a/lib/tsort.rb
+++ b/lib/tsort.rb
@@ -195,18 +195,40 @@ module TSort
   #
   # #each_strongly_connected_component_from doesn't call #tsort_each_node.
   #
-  def each_strongly_connected_component_from(node, id_map={}, stack=[]) # :yields: nodes
+  def each_strongly_connected_component_from(node, id_map={}, stack=[], &block) # :yields: nodes
+    TSort.each_strongly_connected_component_from(node, method(:tsort_each_child), id_map, stack, &block)
+  end
+
+  # Iterates over strongly connected components in a graph.
+  # The graph is represented by _node_ and _each_child_.
+  #
+  # _node_ is the first node.
+  # _each_child_ should have +call+ method which takes a node argument
+  # and yields for each adjacent node.
+  #
+  # Return value is unspecified.
+  #
+  # #TSort.each_strongly_connected_component_from is a class method and
+  # it doesn't need a class to represent a graph which includes TSort.
+  #
+  #   graph = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+  #   each_child = lambda {|n, &b| graph[n].each(&b) }
+  #   TSort.each_strongly_connected_component_from(1, each_child) {|scc|
+  #     p scc #=> [4], [2, 3], [1]
+  #   }
+  #
+  def TSort.each_strongly_connected_component_from(node, each_child, id_map={}, stack=[]) # :yields: nodes
     minimum_id = node_id = id_map[node] = id_map.size
     stack_length = stack.length
     stack << node
 
-    tsort_each_child(node) {|child|
+    each_child.call(node) {|child|
       if id_map.include? child
         child_id = id_map[child]
         minimum_id = child_id if child_id && child_id < minimum_id
       else
         sub_minimum_id =
-          each_strongly_connected_component_from(child, id_map, stack) {|c|
+          TSort.each_strongly_connected_component_from(child, each_child, id_map, stack) {|c|
             yield c
           }
         minimum_id = sub_minimum_id if sub_minimum_id < minimum_id
diff --git a/test/test_tsort.rb b/test/test_tsort.rb
index 38018c49c0..a732064f31 100644
--- a/test/test_tsort.rb
+++ b/test/test_tsort.rb
@@ -40,5 +40,15 @@ class TSortTest < Test::Unit::TestCase # :nodoc:
     assert_equal([[0], [1]],
       a.strongly_connected_components.map {|nodes| nodes.sort})
   end
+
+  def test_noclass
+    g = {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}
+    each_child = lambda {|n, &b| g[n].each(&b) }
+    r = []
+    TSort.each_strongly_connected_component_from(1, each_child) {|scc|
+      r << scc
+    }
+    assert_equal([[4], [2, 3], [1]], r)
+  end
 end