tsort_each

The iterator version of the #tsort method. obj.tsort_each is similar to obj.tsort.each, but modification of obj during the iteration may lead to unexpected results.

#tsort_each returns nil. If there is a cycle, TSort::Cyclic is raised.

class G
  include TSort
  def initialize(g)
    @g = g
  end
  def tsort_each_child(n, &b) @g[n].each(&b) end
  def tsort_each_node(&b) @g.each_key(&b) end
end

graph = G.new({1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]})
graph.tsort_each {|n| p n }
#=> 4
#   2
#   3
#   1