concepts.md

What are state machines?

The point of state machines is to really nail down what something means, and how it works.

However, FSMs have been around for decades, and have been extended by a wide range of people in a wide range of languages. These individuals have used a diversity of language for similar or identical features.

As such, let's start with some basic vocabulary.

Concepts

• state
  • The nodes of the graph.
  • Here, there are four states: Red, Green, Yellow, and Off
  • The finite state machine is always in exactly one state.
  • Other than during hooks, where the past and future state may be validated in parallel, there is no "in-between" or overlap. To the outside world, the transition between states is atomic.
• transition
  • The edges of the graph.
  • Here, there are seven edges, though one may not be obvious:
    • Three for the colors' switching:
      1. From Red to Green
      2. From Green to Yellow
      3. From Yellow to Red
    • Three for each color turning off:
      1. From Green to Off
      2. From Yellow to Off
      3. From Red to Off
    • One for turning the light on
      1. From Off to Red
         • this one can be hard to notice, since it's between the same two edges as #6 - it's visible on the graph as a doubled edge