:states

:states is a basic Finite State Machine (FSM) package for the Arturo Programming language

At a Glance

Inspiration

This package was highly inspired by Harrington Joseph's ¹ talk "When Booleans Are Not Enough... State Machines?" ². By consequence, this is inspired by the pytransitions package.

Tip
If you want to know why you need a FSM, I recommend you to watch his talk first.

Trying :states

Defining a finite state-machine is simple like that:

import {states}!

turnstile: to :states ['locked [
    push        /  locked    ~>  locked
    push        /  unlocked  ~>  locked
    insertCoin  /  locked    ~>  unlocked
    insertCoin  /  unlocked  ~>  unlocked
]]

Explanation

• The first parameter is the initial state,
• The second parameter is the definition os the transitions, this must follow the following order: event, source, fate, being or not separated by symbols.
• You can choose what symbol to use to separate them, or even choose by don't use them, making this a trilema.

Getting the current state

To get the current state, you must call the state method:

turnstile\state 
; => locked

Transitioning between states

There are two equivalent ways of transitioning between states, you can use <fsm>/<event> or <fsm>\changeFrom '<event>:

turnstile\state                   
; => locked
turnstile\push                   
; => locked
turnstile\insertCoin             
; => unlocked
turnstile\insertCoin             
; => unlocked

turnstile\changeFrom 'push       
; => locked
turnstile\changeFrom 'insertCoin 
; => unlocked

Background photo on "At a Glance" by Jack Anstey on Unsplash