Experimental parser: cleanup transition iteration a little

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 41 matching lines @@
     self.__transitions[key] = state
 
   def transitions(self):
     return self.__transitions
 
   def epsilon_closure_iter(self):
     return iter([])
 
   # TODO abstract state matching
   def __matches(self, match_func, value):
-    # f collects states whose corresponding TransitionKey matches 'value'.
-    f = (lambda acc, (key, state):
-           acc | set([state]) if match_func(key, value) else acc)
-    return reduce(f, self.__transitions.items(), set())
+    items = self.__transitions.items()
+    return [state for (key, state) in items if match_func(key, value)]
 
   def transition_state_iter_for_char(self, value):
     return iter(self.__matches(lambda k, v : k.matches_char(v), value))
 
   def transition_state_iter_for_key(self, value):
     return iter(self.__matches(lambda k, v : k.is_superset_of_key(v), value))
 
   def transition_state_for_key(self, value):
     matches = self.__matches(lambda k, v : k.is_superset_of_key(v), value)
     if not matches:
       return None
     # Since this is a dfa, we should have at most one such state. Return it.
     assert len(matches) == 1
-    return iter(matches).next()
+    return matches[0]
 
 class Dfa(Automaton):
 
   def __init__(self, start_name, mapping):
     super(Dfa, self).__init__()
     self.__terminal_set = set()
     name_map = {}
     for name, node_data in mapping.items():
       node = DfaState(name, node_data['action'])
       name_map[name] = node
@@ skipping 260 matching lines @@
           elif len(intersection) <= len(difference):
             working_set.add(intersection)
           else:
             working_set.add(difference)
         if old_partitions:
           partitions -= old_partitions
         if new_partitions:
           partitions |= new_partitions
     (start_name, mapping) = self.__merge_partitions(partitions)
     return Dfa(start_name, mapping)