fsm

check finite state machine properties

npm install fsm
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fsm

check properties of finite state machines.

There is a lot of academic research in this area, yet this module is very simple. There are a lot of fancy tools available, but they are not easy to use. If idea is really useful, then I think a very simple tool should be viable.

Example

Define FSM as json, here is a stream with 4 states. This FSM expresses the constraint that the stream must not emit 'data' when paused, and also that it must not emit data after 'end'.

{
  START: {
    data   : 'START',
    pause  : 'PAUSED',
    end    : 'END',
    error  : 'ERROR'
  },
  PAUSED: {
    pause  : 'PAUSED',
    resume : 'START',
    error  : 'ERROR'
  },
  ERROR: {},
  END: {}
}

we can check a number of properties of this machine. does this machine halt? (and in the right place?) can you reach every state from every other?

API

validate (fsm)

check that all transitions are to defined states.

reachable (fsm)

calculate all states can reach each other states. the result is in the form of

{STATE1: {STATE2: [event path from S1 to S2]}}

terminal (fsm)

return the list of states that cannot reach another state.

alias: `deadlock'

livelock (fsm, [terminal])

get list of states that cannot reach a terminal state.

combine(fsm1, fsm2, start1, start2)

combine two fsm into one, obeying all the transitions in each. TODO: throw an error if there are transitions that are impossible in the combined machine.

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