Experimental parser: subclass for common code

tools/lexer_generator/automaton.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
+#       with the distribution.
+#     * Neither the name of Google Inc. nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+from types import TupleType
+from transition_keys import TransitionKey
+
+class Action(object):
+  pass
+
+class AutomatonState(object):
+
+  def __init__(self, node_number):
+    self.__node_number = node_number
+
+  def node_number(self):
+    return self.__node_number
+
+class Automaton(object):
+
+  @staticmethod
+  def visit_edges(edge, compute_next_edge, visitor, state):
+    visited = set()
+    while edge:
+      f = lambda (next_edge, state), node: (
+        next_edge | compute_next_edge(node),
+        visitor(node, state))
+      (next_edge, state) = reduce(f, edge, (set(), state))
+      visited |= edge
+      edge = next_edge - visited
+    return state
+
+  @staticmethod
+  def generate_dot(start_node, terminal_set, edge_iterator):
+
+    def f(node, node_content):
+      for key, values in node.transitions().items():
+        if key == TransitionKey.epsilon():
+          key = "ε"
+        key = str(key).replace('\\', '\\\\')
+        # TODO pass this action as parameter
+        if type(values) == TupleType:
+          values = [values]
+        for (state, action) in values:
+          if action:
+            node_content.append(
+                "  S_%s -> S_%s [ label = \"%s {%s} -> %s\" ];" %
+                (node.node_number(), state.node_number(), key, action[1],
+                 action[2]))
+          else:
+            node_content.append(
+                "  S_%s -> S_%s [ label = \"%s\" ];" %
+                (node.node_number(), state.node_number(), key))
+      return node_content
+
+    node_content = edge_iterator(f, [])
+    terminals = ["S_%d;" % x.node_number() for x in terminal_set]
+    start_number = start_node.node_number()
+    start_shape = "circle"
+    if start_node in 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))