Expressing queries as finite state automata

When you enter the house, you can press one of the 2 push buttons you have, p1 or p2. Our real world scenario is this: we have a house, with one door, 2 buttons and 3 lights.ДЄt the default state the lights are all turned off. LetвЂ™s model another Finite State Machine now. A Finite State Machine with more complex State Transitions In our simple case, given any state of the machine we just have one logical state to go to, so the table and the chart I made are very, very simple.Д«ut when your system starts to get more complex, itвЂ™s very helpful to have such diagrams and analysis in place because you can reason about your application much easier than by simply keeping everything in your head. We can also model it with a state transition table, which shows the state the machine is currently in, what is the input it receives, what is the next state, and the output: State After this, the semaphore gets back to the green state and the cycle continues indefinitely, until the electricity halts and the semaphore resets when it gets the power again. We have 8 seconds of yellow state, then we move to the red state, and we sit there for 32 seconds, because that road is secondary and it deserves less time of green. We have a timer that after 50 seconds of green state, moves the semaphore into the yellow state. LetвЂ™s say our traffic lights start, when we reset them, at the green state. LetвЂ™s focus on 1 single traffic semaphore.ДЄs we said above, we have 3 states, which can call green, red, yellow. ThatвЂ™s another finite state machine, which contains multiple different finite state machines for each traffic lights device installed for each side of each road of an intersection, which work in sync.ДonвЂ™t think about it now. Of course traffic lights do not exist in isolation. There are many more examples of finite state machines we could use:Д«ut letвЂ™s stick to our traffic lights example, which is very simple and we can reason about it easily. We canвЂ™t define it in a finite number of states.Д«ut traffic lights? ThatвЂ™s a simple thing, and it has 3 states, like we said above. Like the world ecosystem model, or the life of an insect. Some systems might have an infinite number of states. Our traffic lights state machine is said to be finite because we have a finite number of states. In a state machine, the state can only change (and we have a transition) in response to an input. Some semaphores have a button that pedestrian can press to cause the red to display to cars, and that would be another input. The timer in this case is the input of the system. The traffic semaphore will change state when it receives an input, typically just a fixed timer that decides how much time the traffic lights should be green, yellow and red. In State Machines terminology, lights being on or off is called output.Д®ach of those 3 scenarios is called state. (Some semaphores are slightly different, but we donвЂ™t care for the sake of this example) as the yellow light on, and the other 2 lights off.has the red light on, and the other 2 lights off.has the green light on, and the other 2 lights off.The most popular and commonly found example is traffic lights.ДЄt any point in time, a traffic semaphore has a defined state. After reading this tutorial, I am sure youвЂ™ll point out objects in the real world saying to your friends вЂњthatвЂ™s a state machineвЂќ (depending on the nerdy level of your friends). You can see them everywhere, but perhaps you didnвЂ™t think of them as such. State MachinesД«efore looking into what a Finite State Machine is, I want to first introduce what a State Machine is. I like to simplify things, and I decided to write a little explanation for normal human beings, not theoretical or anything made to pass an exam. I did find a lot of information, and of course being textbooks things are made more complex than needed (IMHO). I found the topic of Finite State Machines applied to Frontend Engineering pretty amazing, and I went back to my old books to see if I could find a good explanation of them. This Digital Design course was about encoding information, boolean algebra, combinatorial networks, sequential circuits, sequential state machines, arithmetical circuits, VHDL, and more. I have first met Finite State Machines and Automata back in High School, 20 years ago, then I met them again in my Digital Design course at the University. ThereвЂ™s this popular library called XState, with more than 11000 stars on GitHub, which I run into lately, and I keep reading about it on Twitter and other places. ThereвЂ™s a lot of talk about Finite State Machines these days in JavaScript land.

Expressing queries as finite state automata