tclementdev

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

• You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.

• Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

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,

davidnunez

pm list packages -f

davbeck

#pragma mark - WKUIDelegate

- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)())completionHandler
{
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil
                                                                   message:message
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    [alert addAction:[UIAlertAction actionWithTitle:NSLocalizedString(@"OK", nil) style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
        completionHandler();

kainosnoema

import Foundation

go(println("in a thread"))

// buffered channel
var c = Chan(buffer:20)

// sending routing
go {
    while(true) {

nubbel

protocol ArrayRepresentable {
    typealias ArrayType
    
    func toArray() -> ArrayType[]
}

extension Range : ArrayRepresentable {
    func toArray() -> T[] {
        return T[](self)
    }

mattt

// See: https://devforums.apple.com/message/1000934#1000934

import Foundation

// Logic

operator prefix ¬ {}
@prefix func ¬ (value: Bool) -> Bool {
    return !value
}

cocoalabs

man() {
	env \
		LESS_TERMCAP_mb=$(printf "\e[1;31m") \
		LESS_TERMCAP_md=$(printf "\e[1;31m") \
		LESS_TERMCAP_me=$(printf "\e[0m") \
		LESS_TERMCAP_se=$(printf "\e[0m") \
		LESS_TERMCAP_so=$(printf "\e[1;44;33m") \
		LESS_TERMCAP_ue=$(printf "\e[0m") \
		LESS_TERMCAP_us=$(printf "\e[1;32m") \
			man "$@"

calebd

extension Array {
    
    func first() -> Element? {
        if isEmpty {
            return nil
        }
        return self[0]
    }
    
    func last() -> Element? {

kongtomorrow

/* The Y combinator in Swift!

For a discussion of what the heck this is all about, see http://www.ece.uc.edu/~franco/C511/html/Scheme/ycomb.html

The nifty thing is that it allows us to implement recursion without the ability for a function to refer to itself from within its own definition. 

Note how we manage a recursive definition of factorial without any function referring to its own name.

Thanks to @eridius for help with the SelfToUnderlying<T> type.
*/