Experimental Parser: move key functions to TransitionKey class

tools/lexer_generator/dfa.py

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 29 matching lines @@
   def node_number(self):
     return self.__node_number
 
   def add_transition(self, key, state):
     assert not self.__transitions.has_key(key)
     self.__transitions[key] = state
 
   def transitions(self):
     return self.__transitions
 
-
 class Dfa:
 
   def __init__(self, start_name, mapping, end_names):
     name_map = {}
     offset = 0
     self.__terminal_set = set()
     for name in mapping.keys():
       dfa_state = DfaState(name, offset)
       name_map[name] = dfa_state
       offset = offset + 1
       if name in end_names:
         self.__terminal_set.add(dfa_state)
     for name, values in mapping.items():
       for key, value in values.items():
         name_map[name].add_transition(key, name_map[value])
     self.__start = name_map[start_name]
     assert self.__terminal_set
 
   @staticmethod
   def __visit_edges(start, function, state):
     edge = set([start])
     visited = set()
     while edge:
       next_edge = set()
       for node in edge:
-        next_edge = next_edge | set(node.transitions().values())
+        next_edge |= set(node.transitions().values())
         state = function(node, state)
-      visited = visited | edge
+      visited |= edge
       edge = next_edge - visited
     return state
 
   def to_dot(self):
 
     def f(node, node_content):
       for key, value in node.transitions().items():
         node_content.append(
           "  S_%s -> S_%s [ label = \"%s\" ];" %
             (node.node_number(), value.node_number(), key))
       return node_content
 
     node_content = self.__visit_edges(self.__start, f, [])
     terminals = ["S_%d;" % x.node_number() for x in self.__terminal_set]
     start_number = self.__start.node_number()
     start_shape = "circle"
     if self.__start in self.__terminal_set:
       start_shape = "doublecircle"
 
     return '''
 digraph finite_state_machine {
   rankdir=LR;
   node [shape = %s, style=filled, bgcolor=lightgrey]; S_%s
   node [shape = doublecircle, style=unfilled]; %s
   node [shape = circle];
 %s
 }
-    ''' % (start_shape, start_number, " ".join(terminals), "\n".join(node_content))
-
+    ''' % (start_shape,
+           start_number,
+           " ".join(terminals),
+           "\n".join(node_content))