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Maurice achtenhagen

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andymatuschak /
Last active April 26, 2023 04:56
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,

mdelete / gist:d9dbc320d5de347c2a85
Created May 23, 2015 20:11
Swift iOS SSL public key pinning
View gist:d9dbc320d5de347c2a85
func connection(connection: NSURLConnection, didReceiveAuthenticationChallenge challenge: NSURLAuthenticationChallenge) {
if(challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust) {
var localTrust: Unmanaged<SecTrust>?
let serverTrust = challenge.protectionSpace.serverTrust!
let serverPublicKey = SecTrustCopyPublicKey(serverTrust).takeRetainedValue();
let certificateData = NSData(contentsOfFile: NSBundle.mainBundle().pathForResource("pinning-certificate", ofType: "der")!)
let localCertificate = SecCertificateCreateWithData(kCFAllocatorDefault, certificateData).takeRetainedValue();
let policy = SecPolicyCreateBasicX509().takeRetainedValue()
if SecTrustCreateWithCertificates(localCertificate, policy, &localTrust) == errSecSuccess {
jhermann /
Last active September 8, 2022 08:15
Useful emoji for git commit messages

Useful emoji for git commit messages

If you add emoji to your commit messages for a GitHub repo, they become less boring, and you can convey the kind of change you're adding. See the full set of GitHub supported emoji here (also useful for easy copy&paste via a simple click).

Example commit message

The following is a possible scheme to use:

staltz /
Last active June 2, 2023 13:29
The introduction to Reactive Programming you've been missing
marcedwards / high-dpi-media.css
Last active February 23, 2023 20:01
A CSS media query that captures almost all high DPI aware devices.
View high-dpi-media.css
/* ---------------------------------------------------------- */
/* */
/* A media query that captures: */
/* */
/* - Retina iOS devices */
/* - Retina Macs running Safari */
/* - High DPI Windows PCs running IE 8 and above */
/* - Low DPI Windows PCs running IE, zoomed in */
/* - Low DPI Windows PCs and Macs running Firefox, zoomed in */
/* - Android hdpi devices and above */