andymatuschak

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,

keyboardr

#if (${PACKAGE_NAME} && ${PACKAGE_NAME} != "")package ${PACKAGE_NAME};#end

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;

#parse("File Header.java")
public class ${NAME} extends Fragment {
    
  private static final String FRAG_TAG = ${NAME}.class.getCanonicalName();

twotwotwo

github.com/twotwotwo/sorts is a Go package with parallel radix- and quicksorts. It can run up to 5x faster than stdlib sort on the right kind of large sort task, so it could be useful for analysis and indexing/database-y work in which you have to sort millions of items. (To be clear, I don't recommend most folks drop stdlib sort, which is great, and which sorts depends on.)

While the process of writing it's fresh on my mind, here are some technical details, some things that didn't make the cut, and some thoughts about the process:

Concretely, what this looks like inside:

• Both number and string versions are in-place MSD radix sorts that look at a byte at a time and, once the range being sorted gets down to 128 items, call (essentially) the stdlib's quicksort.

• The [parallelization code

nolanlawson

// Promise.all is good for executing many promises at once
Promise.all([
  promise1,
  promise2
]);

// Promise.resolve is good for wrapping synchronous code
Promise.resolve().then(function () {
  if (somethingIsNotRight()) {
    throw new Error("I will be rejected asynchronously!");

chrisbanes

/*
 * Copyright 2014 Chris Banes
 *
 * 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
 *
 * Unless required by applicable law or agreed to in writing, software

gabrielemariotti

You can use this class to realize a simple sectioned RecyclerView.Adapter without changing your code.

The RecyclerView should use a LinearLayoutManager. You can use this code also with the TwoWayView with the ListLayoutManager (https://github.com/lucasr/twoway-view)

This is a porting of the class SimpleSectionedListAdapter provided by Google

Example:

dmarcato

def toCamelCase(String string) {
    String result = ""
    string.findAll("[^\\W]+") { String word ->
        result += word.capitalize()
    }
    return result
}

afterEvaluate { project ->
    Configuration runtimeConfiguration = project.configurations.getByName('compile')

chrisbanes

/*
 * Copyright 2014 Chris Banes
 *
 * 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
 *
 * Unless required by applicable law or agreed to in writing, software

arobson

Abstraction Suggestions

Summary: use good/established messaging patterns like Enterprise Integration Patterns. Don't make up your own. Don't expose transport implementation details to your application.

Broker

As much as possible, I prefer to hide Rabbit's implementation details from my application. In .Net we have a Broker abstraction that can communicate through a lot of different transports (rabbit just happens to be our preferred one). The broker allows us to expose a very simple API which is basically:

• publish
• request
• start/stop subscription