5

鉴于这些 F# 类型声明...

type Message =
    | MessageA
    | MessageB
    | MessageC
    | MessageD

type State = {
    Name:string
    NextStateMap: Map<Message,State>
}

...这个特定的状态机是否有同样富有表现力的定义...

let rec state0 = { Name = "0"; NextStateMap = Map.ofList [ (MessageA,state1); (MessageB,state2)] }
    and state1 = { Name = "1"; NextStateMap = Map.ofList [ (MessageB,state3)] }
    and state2 = { Name = "2"; NextStateMap = Map.ofList [ (MessageA,state3)] }
    and state3 = { Name = "3"; NextStateMap = Map.ofList [ (MessageC,state4)] }
    and state4 = { Name = "4"; NextStateMap = Map.ofList [ (MessageD,state5)] }
    and state5 = { Name = "5"; NextStateMap = Map.empty}

...使用 Python？

请注意，通过“rec”，我们不必按照拓扑排序定义的顺序进行分配......（例如，state0 是根据 state1 定义的，即使 state1 稍后定义）。

PS 使用字符串作为状态标识符的选项...

stateMachine = {
   "0" : { "A":"1", "B":"2"},
   "1" : { "B":"3" },
...

...保留无效键的情况（即状态机中的无效消息说明符）。

4

2 回答 2

5

在 Python 中，我认为您会定义状态，然后设置地图。伪代码如：

state0 = State("0")
state1 = State("1")
... and so on ...
state0.next_states = {message_a: state1, message_b: state2 }
state1.next_states = {message_b: state3}
... and so on ...
于 2011-02-25T16:01:00.757 回答
0 
## a generic state machine framework ###################

class Message(object):
    """
    This represents a message being passed to the
    state machine.
    """
    def __init__(self, name):
        self.name = name
    def __str__(self):
        return "Message(%r)" % self.name
    def __call__(self, smap):
        try:
            return smap[self]
        except KeyError:
            raise Exception("invalid message: %s vs %s"
                            % (self, smap))

class MessageFactory(object):
    """
    Since python doesn't have symbols, this automagically
    creates the messages for you. (It's purely for
    convenience, and you could just as easily instantiate
    each message by hand.
    """
    cache = {}
    def __getattr__(self, name):
        return self.cache.setdefault(name, Message(name))

class StateMachine(object):
    """
    This keeps track of the state, of course. :)
    """
    def __init__(self, state):
        self.state = state
    def __call__(self, msg):
        self.state = self.state(msg)


## how to set it up: ###################################

msg = MessageFactory()
state =\
{
    0 : lambda m: m({ msg.A : state[1],
                      msg.B : state[2] }),
    1 : lambda m: m({ msg.B : state[3] }),
    2 : lambda m: m({ msg.A : state[3] }),
    3 : lambda m: m({ msg.C : state[4] }),
    4 : lambda m: m({ msg.D : state[5] }),
    5 : lambda m: m({ }),
}

## how to use it: ######################################

s = StateMachine(state[0])
s(msg.A)
assert s.state is state[1]
于 2011-02-25T16:52:19.397 回答