James Rossfeld jrossfeld

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

Better local require() paths for Node.js

Problem

When the directory structure of your Node.js application (not library!) has some depth, you end up with a lot of annoying relative paths in your require calls like:

const Article = require('../../../../app/models/article');

Those suck for maintenance and they're ugly.

Possible solutions

What is your folder-structure preference for a large-scale Node.js project?

0: Starting from Rails

This is the reference point. All the other options are based off this.

|-- app
|   |-- controllers
|   |   |-- admin

	## Unity ##

	*.cs diff=csharp text
	*.cginc text
	*.shader text

	*.mat merge=unityyamlmerge eol=lf
	*.anim merge=unityyamlmerge eol=lf
	*.unity merge=unityyamlmerge eol=lf
	*.prefab merge=unityyamlmerge eol=lf

	import UIKit

	extension UIImage {

	// colorize image with given tint color
	// this is similar to Photoshop's "Color" layer blend mode
	// this is perfect for non-greyscale source images, and images that have both highlights and shadows that should be preserved
	// white will stay white and black will stay black as the lightness of the image is preserved
	func tint(tintColor: UIColor) -> UIImage {

	#!/bin/sh

	# PATH TO YOUR HOSTS FILE
	ETC_HOSTS=/etc/hosts

	# DEFAULT IP FOR HOSTNAME
	IP="127.0.0.1"

	# Hostname to add/remove.
	HOSTNAME=$1

	// #!Swift-1.1
	import Foundation


	// MARK: - (1) classes

	// Solution 1:
	// - Use classes instead of struct
	// Issue: Violate the concept of moving model to the value layer
	// http://realm.io/news/andy-matuschak-controlling-complexity/

	/// Observes a run loop to detect any stalling or blocking that occurs.
	///
	/// This class is thread-safe.
	@interface GHRunLoopWatchdog : NSObject

	/// Initializes the receiver to watch the specified run loop, using a default
	/// stalling threshold.
	- (id)initWithRunLoop:(CFRunLoopRef)runLoop;

	/// Initializes the receiver to detect when the specified run loop blocks for

	/**
	* Copyright 2012 Calvin Rien
	* (http://the.darktable.com)
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*