On Thursday, I did not write anything about that day in my apprenticeship because I was still learning about and trying to absorb the concepts of Finite State Machines (FSMs).
On Friday, I did not write anything because I was pooped. So here I am tonight writing about both days.
At first, the concept of a Finite State Machine was a little fuzzy. I sort of understood it, partially thanks to Eric’s drawings on some glass which helped. The basics of it, so far as I understand it, is that there is an object which contains a single “state”, a defined set of initial states and end states, events which trigger a transition from one state to another, and (optionally) actions to be performed at each transition.
The reason it’s called finite is because each state that could possibly arise in the state machine, and each transition between them, is entirely defined before the state machine is every run.
So, for example, one of those “choose-your-own-adventure” games (like Zork!) could represent a finite state machine. At each “turn”, you start at the initial state. Once you “take your turn”, the turn represents the event, which triggers an action (you die, find a treasure chest, encounter a monster, etc), and afterwards are moved to another state (dead, rich, hyperarousal, etc).
So that’s the basics of a state machine. My intentions were to use it to create a “markdown-like-language” parser for the Ruby Wiki I’m writing as a project designated by Eric. The language is simple right now, consisting only of emphasis, strong, and paragraph controls. Originally it was implemented as regular expressions (which Skim helped me with, thanks Skim!) but that was a bit fragile, plus it evaded the whole learning-FSM thing, which will undoubtedly come in handy later.
Initially I tried to implement the state machine as
case..when..end Ruby statement, but that turned out to be kind of ugly, albeit it worked. Later on, I changed it to being an array of 4-element arrays (representing the initial-state, trigger-event, next-state, and optional-action). It then constituted a State Transition Table (STT), which is one implementation method for a FSM. One benefit of a STT is that the logic for enumerating the table and acting on the FSM’s logic is then separated completely from the data of the STT itself.
Another usage of FSMs, by the way, could be Graphical User Interfaces (GUIs) — I’m starting to think we just love giving everything a TLA so that we sound smarter — because if you really think about it, the GUI is always in a given state, and a user-based or internal-based event triggers it to transition into the next state. Sometimes this causes an action. For example, the initial state could be a blank window. A mouse click, key press, or asynchronous callback function may each be a trigger-event. This event would then redirect the FSM to the state of “having a minimized window”. The action taken, then, would have to correlate to the event, and thus it might be
[window performMinimize] (assuming Cocoa-like/ObjC).
After I had transitioned my state machine from a
when body to a STT two-dimensional table, I tried to make it look less ugly, but failed. So I created my very first DSL much like Builder, which created the STT for me. It’s used to define the body of my state transition table function. Now, it looks more readable and is probably more maintainable and flexible than the array-based version.
Also, it’s not entirely finished. As it only returns the two-dimensional array already built for you, it’s not doing a very good job encapsulating the aspect of a Finite State Machine, it just masks one part of it. So, my plan is to move all of the FSM-related logic into a Builder-like object, so that my
ContentsLexer class will only be required to define the logic and data for the state machine to work, and be able to output its
tokens method — this is the sole purpose of the
ContentsLexer class after all, it just takes in a raw string and tokenizes it for the upcoming
ContentsParser state machine which will transform the tokens into an Abstract Syntax Tree. I could be wrong about how that part will function, though, as I only started my research into it on late Friday. But the idea I have in my head for it is that it will probably be a recursive hash containing an abstract representation of the final markdown syntax.. and when I imagine it, I see Lisp’s s-expressions. But anyway I’m digressing, aren’t I?
According to Eric, FSMs can be used to represent practically everything, as it’s almost a universal principle or rule, much like the Turing Machine, such that everything else more complex can be boiled down into a finite state machine. Given this is true, we can expect that xkcd will soon post a meta-comic about the world actually being a simulation of FSMs.
My name is Steven Degutis, and I've been writing software professionally for a decade. During that time, I've written many apps and websites, quite a few technical articles, and kept up-to-date with the rapidly evolving software industry.
If you have software needs for web, mobile, or desktop, and are looking for a seasoned software professional, please reach out to me at email@example.com to set up a phone call.
- Self-employed – present
- Clean Coders – 5 years
- 8th Light – 2 years
- Big Nerd Ranch – 1 year
- Self-employed - 1 year
- Web: full-stack
- iOS (UIKit)
- macOS (Cocoa)
- REST APIs
- AWS / EC2 / ELB
- HTML5 / CSS
Over the past decade, I've written a total of 169 technical articles on various programming languages, frameworks, best practices, and my own projects, as I kept up-to-date and active in the software industry.
Subscribe via RSS / Atom.
- 2017 — "Clean code" isn't actually clean
- 2017 — Passion in your field is overrated
- 2017 — What I learned in 5 days of writing an experimental website
- 2014 — Age of the Polyglot
- 2013 — How to Program
- 2013 — Ignore the Naysayers
- 2013 — Writing Clearly
- 2012 — Reinvent the wheel
- 2010 — Good usability
- 2009 — Twitter is the wrong tool
- 2009 — We're all pretty bad at driving
- 2008 — Why I Code
|March||Notes on Haskell Extensions|
|February||Second thoughts on front-end tools|
|February||First thoughts on front-end tools|
|February||Some thoughts on GUIs|
|February||First thoughts on OCaml|
|February||First thoughts on Haskell|
|August||Age of the Polyglot|
|August||The history of Mjolnir|
|August||Quitting the GUI wars|
|June||Lua: my new favorite extension language|
|January||My programming life-goals|
|January||Lingua Latina, Pars I|
|January||Allocating an AST on the stack|
|April||Ruby Accessors Considered Pernicious|
|March||Reinvent the wheel|
Here are some of the projects I'm most proud of. They were created using a variety of technologies, running on several different platforms and OSes. They're all finished products, and many of them are open source.
I made Docks in 2009 for users who wanted to swap out icons in their Dock with a single click. Its unique functionality and design aesthetic attracted the attention of Apple, Engadget, MacWorld, and led to an acquisition of my start-up by Big Nerd Ranch.
This toy was made in a weekend to entertain my 1 year old daughter. It lets you create bubbles with your fingers, which then simulate physics by bumping into each other and falling.
When I couldn't find an app in the App Store that let me make very simple lists extremely quickly, I made one myself. I use it almost every day to organize and track my activities.
I created this app to increase my productivity by letting me move windows around in macOS using keyboard shortcuts. It grew into a community-driven highly extensible app, using Lua for its plugin system.
Implementing this elite social network gave me experience integrating both Apple Pay and credit card payments (via Stripe.com) seamlessly into web apps, for a frictionless and pain-free payment experience.
This isn't just any chatroom. In this web app, you can see what everyone is typing while they type it. I made this in order to scratch my itch for making real-time apps and games, and learned how to use WebSockets in the process.
This was written in 2009, before the time of Slack, when IRC was the main way for programmers to get short-term assistance from each other. Its purpose was to be a beautiful app with an emphasis on simplicity and usability over technical power.
This is an app I actually use every single day. It lets you move windows with global keyboard shortcuts. Since it uses Vim-like key bindings, it should feel pretty natural to any programmer. There's no configuration needed; it Just Works™.
As an evolution of Phoenix, Hydra was my first attempt at embedding a full Lua virtual machine into an Objective-C app, to make a lightweight and efficient window manager that focused on speed, low memory usage, low CPU usage, and overall being gentle on laptop batteries.
These may be tiny, but they're interesting technical feats.
|Lua4Swift||Swift framework for embedding Lua with a native Swift API.|
|choose||Command line fuzzy-matching tool for macOS that uses a GUI|
|music||Command line music daemon for macOS that only speaks JSON|
|hecto||Command line text editor with an embedded Lua plugin system|
|ZephSharp||Window manager for Windows using Clojure for scripting|
|management||Minimalist EC2 configuration & deployment tool in Ruby.|
|go.assert||Assertion helper package for writing tests in Go.|
|go.shattr||Go library for printing shell-attributed strings to stdout.|
|OCDSpec2||Objective-C based testing framework with Xcode integration.|