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,

steipete

# The trick is to link the DeviceSupport folder from the beta to the stable version.
# sudo needed if you run the Mac App Store version. Always download the dmg instead... you'll thank me later :)

# Support iOS 15 devices (Xcode 13.0) with Xcode 12.5:
sudo ln -s /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/15.0 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

# Then restart Xcode and reconnect your devices. You will need to do that for every beta of future iOS versions

# (A similar approach works for older versions too, just change the version number after DeviceSupport)

Catfish-Man

// Compile with clang -framework Foundation sethack.m

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

/*
 CFHashBytes from http://www.opensource.apple.com/source/CF/CF-1153.18/CFUtilities.c
 */
#define ELF_STEP(B) T1 = (H << 4) + B; T2 = T1 & 0xF0000000; if (T2) T1 ^= (T2 >> 24); T1 &= (~T2); H = T1;

uliwitness

You can specify the underlying name for a C function the linker/compiler should actually use. If you use an existing
function's name, it will just let you refer to it with your prototype's name. If you define the function, it'll give
it that name. It even complains if a function of that name already exists. Tested with clang on a Mac, but AFAIK also
works in GCC. You can even use special characters in your function names, like you can do in assembly.

yiding

{-# LANGUAGE OverloadedStrings #-}
module DGPHParser(parseDgph) where

import qualified Data.Attoparsec.ByteString as A
import qualified Data.ByteString as B
import Data.Bits
import Data.Foldable (foldl')
import qualified Data.ByteString as B
import qualified Data.Attoparsec.ByteString as A

erica

public struct Error: ErrorType {
    let source: String; let reason: String
    public init(_ source: String = __FILE__, _ reason: String) {
        self.reason = reason; self.source = source
    }
}

protocol Contextualizable {}
extension Contextualizable {
    func functionContext(function : String = __FUNCTION__) -> String {

cb372

Category theory jargon cheat sheet

A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)

I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.

Functor

A functor is something that supports map.

drewmccormack

#!/usr/bin/env bash

# If your OS X WiFi connection stops working, but can be fixed by 
# toggling WiFi off and then on, this script can help prevent mouse arm.
# Pings Apple's server repeatedly, toggling WiFi off/on when a connection times out.
while true ; do
  curl --head --silent --connect-timeout 10 http://www.apple.com/my-wifi-keeps-dropping-out > /dev/null
  if [ $? -ne 0 ] ; then
    networksetup -setairportpower en1 off
    networksetup -setairportpower en1 on

clementgenzmer

/*
 * This is an example provided by Facebook are for non-commercial testing and
 * evaluation purposes only.
 *
 * Facebook reserves all rights not expressly granted.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
 * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN

steipete

// hpp:

/// A smart pointer that can manage the lifecycle of Core Foundation objects.
template<typename T>
class CFPointer {
public:
    CFPointer() : storage(nullptr) { }

    CFPointer(T pointer) : storage(toStorageType(pointer)) {
        if (storage) {