Keita Ito keitaito

State of String: ABI, Performance, Ergonomics, and You!

Hello, I’ve been working on implementing, optimizing, and improving String in preparation for ABI stability, and I thought I’d share the current status of String in Swift 5 and some potential directions to go. This is the product of conversations with open source contributors and my colleagues on the Swift standard library team at Apple.

The primary area of focus is stabilizing String’s ABI, but we’d be remiss if we couldn’t also fit in performance and ergonomic improvements. String’s ergonomics in particular is one area where we think the status quo is woefully inadequate, and over half of this email is devoted to that topic. At the end, there’s a section about a community initiative that we hope can help users of String as well as guide future development.

(Note: I’m sending this to swift-dev because much of the contents revolve around implementation concerns. I’ll also cross-reference on swift-evolution and swift-users. See also the [StringManife

Typed error can be useful in certain cases, especially when accompanied with NoError type.

For example, in reactive programming, https://github.com/ReactiveCocoa/ReactiveSwift (typed error) allows us to create UI bindings only if Error is NoError, i.e.:

static func <~ <Source: BindingSource> (provider: Self, source: Source) -> Disposable? 
    where Source.Value == Value, Source.Error == NoError { ... }
    
// example
let alphaSignal: Signal = ...

Keychain API

kSecAttrAccessible Mapping

Protection Domain (pdmn)	Keychain Accessibility Values
`ck`	`kSecAttrAccessibleAfterFirstUnlock`
`cku`	`kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly`
`dk`	`kSecAttrAccessibleAlways`
`akpu`	`kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly`

	Originall From: Posted 2015-05-29 http://ubwg.net/b/full-list-of-ffmpeg-flags-and-options

	This is the complete list that’s outputted by ffmpeg when running ffmpeg -h full.

	usage: ffmpeg [options] [[infile options] -i infile]… {[outfile options] outfile}…

	Getting help:
	-h — print basic options
	-h long — print more options
	-h full — print all options (including all format and codec specific options, very long)

	let str = "acxz"

	func isFunny(_ s: AnySequence<UInt8>) -> Bool {
	let n1: [Int] = zip(s.dropFirst(), s).map { Int($0)-Int($1) }
	let n2: [Int] = zip(s.reversed().dropFirst(), s.reversed()).map { Int($1)-Int($0) }
	return n1 == n2
	}

	isFunny(AnySequence(str.utf8))

	import Foundation

	func fatalerror(_ text : String) {
	fputs(text, __stderrp)
	exit(-1)
	}

	struct ReadingListItem {
	init(title: String?, previewText: String?, url: URL, dateAdded: Date) {
	self.title = title

	enum HTTPStatusCodes: Int {
	// 100 Informational
	case Continue = 100
	case SwitchingProtocols
	case Processing
	// 200 Success
	case OK = 200
	case Created
	case Accepted
	case NonAuthoritativeInformation

	extension Location {
	func closestLocationOnPath(start: Location, end: Location) -> (location: Location, t: Double, distance: Double) {
	let pathVector = (latitude: end.latitude - start.latitude, longitude: end.longitude - start.longitude)
	var t = (self.latitude * pathVector.latitude - start.latitude * pathVector.latitude + self.longitude * pathVector.longitude - start.longitude * pathVector.longitude) / (pow(pathVector.latitude,2) + pow(pathVector.longitude,2))
	t = min(max(t, 0), 1)
	let closestLocation = Location(latitude: start.latitude + t * pathVector.latitude, longitude: start.longitude + t * pathVector.longitude)
	return (location: closestLocation, t: t, distance: distance(to: closestLocation))
	}

	func distance(to other: Location) -> Double {


	var blockOperations: [BlockOperation] = []

	func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {

	if type == NSFetchedResultsChangeType.insert {
	print("Insert Object: \(newIndexPath)")

	blockOperations.append(
	BlockOperation(block: { [weak self] in