Experimental parser: add comments for NfaBuilder.

tools/lexer_generator/nfa_builder.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 11 matching lines @@
 # 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 inspect import getmembers
 from nfa import *
 
+# Nfa is built in two stages:
+# 1. Build a tree of operations on rules.
+#    Each node in the tree is a tuple (operation, subtree1, ... subtreeN).
+#    Rule parser builds this tree by invoking static methods of NfaBuilder.
+# 2. For each node, perform the operation of the node to produce an Nfa.
+#    If an operation is called X, then it is performed by the method
+#    of NfaBuilder called __x(). See __process() for mapping from
+#    operation to processing methods.
+
 class NfaBuilder(object):
 
   def __init__(self, encoding, character_classes = {}):
     self.__node_number = 0
     self.__operation_map = {}
     self.__members = getmembers(self)
     self.__encoding = encoding
     self.__character_classes = character_classes
     self.__states = []
     self.__global_end_node = None
@@ skipping 286 matching lines @@
 
   __modifer_map = {
     '+': 'ONE_OR_MORE',
     '?': 'ZERO_OR_ONE',
     '*': 'ZERO_OR_MORE',
   }
 
   @staticmethod
   def apply_modifier(modifier, graph):
     return (NfaBuilder.__modifer_map[modifier], graph)