Experimental parser: split out NfaBuilder

tools/lexer_generator/nfa_builder.py

Index: tools/lexer_generator/nfa_builder.py
diff --git a/tools/lexer_generator/nfa.py b/tools/lexer_generator/nfa_builder.py
similarity index 55%
copy from tools/lexer_generator/nfa.py
copy to tools/lexer_generator/nfa_builder.py
index cbc9a9f301334fa0803708be70a5acd1fb98bed9..c13c66abcec82f73f7b3660913ab8291b2f6fa94 100644
--- a/tools/lexer_generator/nfa.py
+++ b/tools/lexer_generator/nfa_builder.py
@@ -26,109 +26,10 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 from types import TupleType
-from transition_keys import TransitionKey
-from automaton import *
 from inspect import getmembers
+from nfa import *
 
-class NfaState(AutomatonState):
-
-  def __init__(self, node_number):
-    super(NfaState, self).__init__(node_number)
-    self.__transitions = {}
-    self.__unclosed = set()
-    self.__epsilon_closure = None
-    self.__action = None
-
-  def epsilon_closure(self):
-    return self.__epsilon_closure
-
-  def set_epsilon_closure(self, closure):
-    assert self.is_closed()
-    assert self.__epsilon_closure == None
-    self.__epsilon_closure = frozenset(closure)
-
-  def action(self):
-    assert self.is_closed()
-    return self.__action
-
-  def set_action(self, action):
-    assert not self.is_closed()
-    assert not self.__action
-    self.__action = action
-
-  def transitions(self):
-    assert self.is_closed()
-    return self.__transitions
-
-  def next_states(self, key_filter):
-    assert self.is_closed()
-    f = lambda acc, (k, v) : acc if not key_filter(k) else acc | set(v)
-    return reduce(f, self.__transitions.items(), set())
-
-  def __add_transition(self, key, next_state):
-    if next_state == None:
-      assert not self.is_closed(), "already closed"
-      self.__unclosed.add(key)
-      return
-    if not key in self.__transitions:
-      self.__transitions[key] = set()
-    self.__transitions[key].add(next_state)
-
-  def add_unclosed_transition(self, key):
-    assert key != TransitionKey.epsilon()
-    self.__add_transition(key, None)
-
-  def add_epsilon_transition(self, state):
-    assert state != None
-    self.__add_transition(TransitionKey.epsilon(), state)
-
-  def is_closed(self):
-    return self.__unclosed == None
-
-  def close(self, end):
-    assert not self.is_closed()
-    unclosed, self.__unclosed = self.__unclosed, None
-    if end == None:
-      assert not unclosed
-      return
-    for key in unclosed:
-      self.__add_transition(key, end)
-    if not unclosed:
-      self.__add_transition(TransitionKey.epsilon(), end)
-
-  def __matches(self, match_func, value):
-    f = lambda acc, (k, vs): acc | vs if match_func(k, value) else acc
-    return reduce(f, self.__transitions.items(), set())
-
-  def char_matches(self, value):
-    return self.__matches(lambda k, v : k.matches_char(v), value)
-
-  def key_matches(self, value):
-    return self.__matches(lambda k, v : k.matches_key(v), value)
-
-  def replace_catch_all(self):
-    catch_all = TransitionKey.unique('catch_all')
-    if not catch_all in self.__transitions:
-      return
-    f = lambda acc, state: acc | state.__epsilon_closure
-    reachable_states = reduce(f, self.__transitions[catch_all], set())
-    f = lambda acc, state: acc | set(state.__transitions.keys())
-    keys = reduce(f, reachable_states, set())
-    keys.discard(TransitionKey.epsilon())
-    keys.discard(catch_all)
-    inverse_key = TransitionKey.inverse_key(keys)
-    if inverse_key:
-      self.__transitions[inverse_key] = self.__transitions[catch_all]
-    del self.__transitions[catch_all]
-
-  @staticmethod
-  def gather_transition_keys(state_set):
-    f = lambda acc, state: acc | set(state.__transitions.keys())
-    keys = reduce(f, state_set, set())
-    keys.discard(TransitionKey.epsilon())
-    return TransitionKey.disjoint_keys(keys)
-
-class NfaBuilder:
+class NfaBuilder(object):
 
   def __init__(self):
     self.__node_number = 0
@@ -348,96 +249,3 @@ class NfaBuilder:
   @staticmethod
   def apply_modifier(modifier, graph):
     return (NfaBuilder.__modifer_map[modifier], graph)
-
-class Nfa(Automaton):
-
-  def __init__(self, start, end, nodes_created):
-    super(Nfa, self).__init__()
-    self.__start = start
-    self.__end = end
-    self.__epsilon_closure_computed = False
-    self.__verify(nodes_created)
-
-  def __visit_all_edges(self, visitor, state):
-    edge = set([self.__start])
-    next_edge = lambda node: node.next_states(lambda x : True)
-    return self.visit_edges(edge, next_edge, visitor, state)
-
-  def __verify(self, nodes_created):
-    def f(node, node_list):
-      assert node.is_closed()
-      node_list.append(node)
-      return node_list
-    node_list = self.__visit_all_edges(f, [])
-    assert len(node_list) == nodes_created
-
-  def __compute_epsilon_closures(self):
-    if self.__epsilon_closure_computed:
-      return
-    self.__epsilon_closure_computed = True
-    def outer(node, state):
-      def inner(node, closure):
-        closure.add(node)
-        return closure
-      is_epsilon = lambda k: k == TransitionKey.epsilon()
-      next_edge = lambda node : node.next_states(is_epsilon)
-      edge = next_edge(node)
-      closure = self.visit_edges(edge, next_edge, inner, set())
-      node.set_epsilon_closure(closure)
-    self.__visit_all_edges(outer, None)
-
-  @staticmethod
-  def __close(states):
-    f = lambda acc, node: acc | node.epsilon_closure()
-    return reduce(f, states, set(states))
-
-  def matches(self, string):
-    self.__compute_epsilon_closures()
-    valid_states = Nfa.__close(set([self.__start]))
-    for c in string:
-      f = lambda acc, state: acc | state.char_matches(c)
-      transitions = reduce(f, valid_states, set())
-      if not transitions:
-        return False
-      valid_states = Nfa.__close(transitions)
-    return self.__end in valid_states
-
-  @staticmethod
-  def __to_dfa(nfa_state_set, dfa_nodes, end_node):
-    nfa_state_set = Nfa.__close(nfa_state_set)
-    assert nfa_state_set
-    name = ".".join(str(x.node_number()) for x in sorted(nfa_state_set))
-    if name in dfa_nodes:
-      return name
-    def gather_actions(states):
-      actions = set()
-      for state in states:
-        if state.action():
-          actions.add(state.action())
-      actions = list(actions)
-      actions.sort()
-      return actions
-    dfa_nodes[name] = {
-      'transitions': {},
-      'terminal': end_node in nfa_state_set,
-      'actions' : gather_actions(nfa_state_set)}
-    for key in NfaState.gather_transition_keys(nfa_state_set):
-      match_states = set()
-      f = lambda acc, state: acc | state.key_matches(key)
-      for state in reduce(f, nfa_state_set, set()):
-        match_states.add(state)
-      transition_state = Nfa.__to_dfa(match_states, dfa_nodes, end_node)
-      dfa_nodes[name]['transitions'][key] = transition_state
-    return name
-
-  def compute_dfa(self):
-    self.__compute_epsilon_closures()
-    self.__visit_all_edges(lambda node, state: node.replace_catch_all(), None)
-    dfa_nodes = {}
-    start_name = self.__to_dfa(set([self.__start]), dfa_nodes, self.__end)
-    return (start_name, dfa_nodes)
-
-  def to_dot(self):
-    iterator = lambda visitor, state: self.__visit_all_edges(visitor, state)
-    state_iterator = lambda x : x
-    return self.generate_dot(self.__start, set([self.__end]), iterator, state_iterator)