Move DFA#nil_transition_states to NFA::State

lib/imbecile/regex/dfa.rb

@@ -8,30 +8,7 @@ module Imbecile
         nfas.each do |nfa|
           start_nfa.start_state.add_transition(nil, nfa.start_state)
         end
-        nil_transition_states = nil_transition_states(start_nfa.start_state)
+        nil_transition_states = start_nfa.start_state.nil_transition_states
-      end
-
-      private
-
-      # Determine the set of states that can be reached by nil transitions
-      # from the given state.
-      #
-      # @return [Set<NFA::State>]
-      #   Set of states.
-      def nil_transition_states(state)
-        states = Set[state]
-        analyze_state = lambda do |state|
-          state.transitions.each do |range, dest_state|
-            if range.nil?
-              unless states.include?(dest_state)
-                states << dest_state
-                analyze_state[dest_state]
-              end
-            end
-          end
-        end
-        analyze_state[state]
-        states
       end
 
     end

lib/imbecile/regex/nfa.rb

@@ -16,6 +16,27 @@ module Imbecile
           @transitions << [code_point, destination_state]
         end
 
+        # Determine the set of states that can be reached by nil transitions.
+        # from this state.
+        #
+        # @return [Set<NFA::State>]
+        #   Set of states.
+        def nil_transition_states
+          states = Set[self]
+          analyze_state = lambda do |state|
+            state.transitions.each do |range, dest_state|
+              if range.nil?
+                unless states.include?(dest_state)
+                  states << dest_state
+                  analyze_state[dest_state]
+                end
+              end
+            end
+          end
+          analyze_state[self]
+          states
+        end
+
       end
 
       attr_accessor :start_state