class Node(object):
    def __init__(self, children=None):
        self.children = children
        if self.children is None:
            self.children = []
    def visit(self, callback, *args):
        callback(self, *args)
        for c in self.children:
            c.visit(callback, *args)

class StatementNode(Node):
    def __init__(self, children=None):
        Node.__init__(self, children)

class ExprNode(Node):
    def __init__(self, children=None):
        Node.__init__(self, children)

class CExprNode(ExprNode):
    def __init__(self, cstring):
        ExprNode.__init__(self)
        self.cstring = cstring

class UnitNode(Node):
    def __init__(self, children=None):
        Node.__init__(self, children)

class FunctionNode(Node):
    def __init__(self, name, ret_type, children=None):
        Node.__init__(self, children)
        self.name = name
        self.ret_type = ret_type