    """ Abstract base class for AST nodes.
    """
    def __repr__(self):
        """ Generates a python representation of the current node
        """
        result = self.__class__.__name__ + '('

        indent = ''
        separator = ''
        for name in self.__slots__[:-2]:
            result += separator
            result += indent
            result += name + '=' + (_repr(getattr(self, name)).replace('\n', '\n  ' + (' ' * (len(name) + len(self.__class__.__name__)))))

            separator = ','
            indent = '\n ' + (' ' * len(self.__class__.__name__))

        result += indent + ')'

        return result

    def children(self):
        """ A sequence of all children that are Nodes
        """
        pass

    def show(self, buf=sys.stdout, offset=0, attrnames=False, nodenames=False, showcoord=False, _my_node_name=None):
        """ Pretty print the Node and all its attributes and
            children (recursively) to a buffer.

            buf:
                Open IO buffer into which the Node is printed.

            offset:
                Initial offset (amount of leading spaces)

            attrnames:
                True if you want to see the attribute names in
                name=value pairs. False to only see the values.

            nodenames:
                True if you want to see the actual node names
                within their parents.

            showcoord:
                Do you want the coordinates of each Node to be
                displayed.
        """
        lead = ' ' * offset
        if nodenames and _my_node_name is not None:
            buf.write(lead + self.__class__.__name__+ ' <' + _my_node_name + '>: ')
        else:
            buf.write(lead + self.__class__.__name__+ ': ')

        if self.attr_names:
            if attrnames:
                nvlist = [(n, getattr(self,n)) for n in self.attr_names]
                attrstr = ', '.join('%s=%s' % nv for nv in nvlist)
            else:
                vlist = [getattr(self, n) for n in self.attr_names]
                attrstr = ', '.join('%s' % v for v in vlist)
            buf.write(attrstr)

        if showcoord:
            buf.write(' (at %s)' % self.coord)
        buf.write('\n')

        for (child_name, child) in self.children():
            child.show(
                buf,
                offset=offset + 2,
                attrnames=attrnames,
                nodenames=nodenames,
                showcoord=showcoord,
                _my_node_name=child_name)


class NodeVisitor(object):
    """ A base NodeVisitor class for visiting c_ast nodes.
        Subclass it and define your own visit_XXX methods, where
        XXX is the class name you want to visit with these
        methods.

        For example:

        class ConstantVisitor(NodeVisitor):
            def __init__(self):
                self.values = []

            def visit_Constant(self, node):
                self.values.append(node.value)

        Creates a list of values of all the constant nodes
        encountered below the given node. To use it:

        cv = ConstantVisitor()
        cv.visit(node)

        Notes:

        *   generic_visit() will be called for AST nodes for which
            no visit_XXX method was defined.
        *   The children of nodes for which a visit_XXX was
            defined will not be visited - if you need this, call
            generic_visit() on the node.
            You can use:
                NodeVisitor.generic_visit(self, node)
        *   Modeled after Python's own AST visiting facilities
            (the ast module of Python 3.0)
    """

    _method_cache = None

    def visit(self, node):
        """ Visit a node.
        """

        if self._method_cache is None:
            self._method_cache = {}

        visitor = self._method_cache.get(node.__class__.__name__, None)
        if visitor is None:
            method = 'visit_' + node.__class__.__name__
            visitor = getattr(self, method, self.generic_visit)
            self._method_cache[node.__class__.__name__] = visitor

        return visitor(node)

    def generic_visit(self, node):
        """ Called if no explicit visitor function exists for a
            node. Implements preorder visiting of the node.
        """
        for c in node:
            self.visit(c)

N)