Skip to content

Instantly share code, notes, and snippets.

@monday0rsunday
monday0rsunday / States-v3.md
Created January 18, 2019 09:14 — forked from andymatuschak/States-v3.md
A composable pattern for pure state machines with effects (draft v3)

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,

@monday0rsunday
monday0rsunday / ClassLoaderLeakExample.java
Created May 21, 2016 10:19 — forked from dpryden/ClassLoaderLeakExample.java
Example of a ClassLoader leak in Java
import java.io.IOException;
import java.net.URLClassLoader;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.Path;
/**
* Example demonstrating a ClassLoader leak.
*
* <p>To see it in action, copy this file to a temp directory somewhere,