Tutorial

Intro

Here we will make our first working project using FSME. There's (at least in Russia) a classic joke-problem, which sounds like following dialog:

• How to put a giraffe to the refrigerator in three steps?
• Open the refrigerator, put a giraffe, close the refrigerator
• And how to put a hippopotamus to the refrigerator?
• Open the refrigerator, get giraffe, put hippopotamus, close the frige

The very beginning

First of all, we should create a refrigerator. From the previous page you know how to run FSME and how to create entities in it. So, we should now create a simple refrigerator.

This refrigerator will have two states: "the door is opened" and "the door is closed". Also, there will be 2 events: "Open" and "Close"

• Open FSME, and give automata a name (FrigeFSM)
• Create states Opened and Closed, and events Open and Close. Set Initial State to Closed

Two states and Two events

• Next, we should create transitions. Go to state Closed, press Ins key. You are now in the new transition editor. Give new transition a name, for example, open
• Then create a close transition in the Opened state, putting Close to the transition condition.

Final FSM

Now it is time to make source from this automata. In this tutorial we use Python, but C++ way will be nearly the same. As our FSM does not interact anyhow yet, we would include automatic trace information to see that it works.

• Save drawn FSM to a file, for example, frige.fsm
• Issue a folowing command:

  pyfsmc frige.fsm -o frige.py -d
  

• Create main script (main.py), which contains the following:

  import frige
  f = frige.FrigeFSM()
  f.A(frige.FrigeFSM.Open)
  f.A(frige.FrigeFSM.Close)
  

• Now you can run it to see that it works.

  FrigeFSM:event:'Open'
  FrigeFSM:state:'Closed'
  FrigeFSM:transition:'open'
  FrigeFSM:new state:'Opened'
  FrigeFSM:event:'Close'
  FrigeFSM:state:'Opened'
  FrigeFSM:transition:'close'
  FrigeFSM:new state:'Closed'
  

Introducing light

All good refrigerators turn light on opening, and turn it off on closing. Our frige is not an exception. Let's extend it a bit.

• Create two outputs: turnLightOff and turnLightOn
• Add them to In part Closed and Opened states respectively. This makes FSM to call these outputs on entering appropriate state.
  Note: Adding outputs to outpart makes them to be executed on leaving the state (details)

A FSM with outputs

• Repeat code generation using pyfsmc.
• Now we should derive from frige.FrigeFSM to implement created outputs.

  class LightFrige( frige.FrigeFSM ):
      def turnLightOn(self):
          print "Turning on the light"
      def turnLightOff(self):
          print "Turning off the light"
  

• And call it as before:

  f = LightFrige()
  f.A( frige.FrigeFSM.Open )
  f.A( frige.FrigeFSM.Close )
  

  Output will be the following (if you run pyfsmc without -d):

  Turning on the light
  Turning off the light
  

The Problem itself

Let's solve our problem at last! Draw FSM implementing the logic by yourself :). or take ready FSM from here

A sample FSM look

Hint This FSM will have the following events: PutGiraffe PutHippopotamus states: Empty Giraffe Hippopotamus outputs: openFrige closeFrige getGiraffe getHippopotamus putGiraffe putHippopotamus

Implement your logic:

 from frige         import *
 from frige_logic1  import *

class LightFrige( FrigeFSM ):
    def turnLightOn(self):
        print "Turning on the light"
    def turnLightOff(self):
        print "Turning off the light"

class FrigeLogic( FrigeLogicFSM ):
    def __init__(self, frige):
        super(FrigeLogic, self).__init__()
        self.frige = frige
        
    def putHippopotamus( self ):
        print "Putting Hippopotamus to the frige"

    def getGiraffe( self ):
        print "Getting Giraffe from the frige"

    def putGiraffe( self ):
        print "Putting Giraffe to the frige"

    def openFrige( self ):
        print "Opening frige"
        self.frige.A( FrigeFSM.Open )
        print "Frige opened"

    def closeFrige( self ):
        print "Closing frige"
        self.frige.A( FrigeFSM.Close )
        print "Frige closed"

    def getHippopotamus( self ):
        print "Getting Hippopotamus from the frige"

if __name__=="__main__":
    f = LightFrige()
    l = FrigeLogic( f )
    print "\n*** Putting Giraffe to Frige"
    l.A( FrigeLogicFSM.PutGiraffe )
    print "\n*** Putting Hippopotamus to Frige"
    l.A( FrigeLogicFSM.PutHippopotamus )
    print "\n*** Freeing Frige"
    l.A( FrigeLogicFSM.FreeFrige )

Conclusion