Project 35 --> Project 36
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CypherPoet
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//: [Previous](@previous)
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import UIKit
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import GameplayKit
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// six-sided die
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let d6 = GKRandomDistribution.d6()
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d6.nextInt()
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// twenty-sided die
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let d20 = GKRandomDistribution.d20()
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d20.nextInt()
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let crazyDie = GKRandomDistribution(lowestValue: 20, highestValue: 23508)
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crazyDie.nextInt()
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// ⚠️ Going out of bounds will straight-up crash things, though
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// crazyDie.nextInt(upperBound: 1)
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/// Distributions can have a custom source of randomness
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let twisterEngine = GKMersenneTwisterRandomSource()
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print(GKRandomDistribution(randomSource: twisterEngine, lowestValue: 10, highestValue: 1000).nextInt())
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/**
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Sometimes, though, we don't want completely realistic randomness: We might
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want to avoid repeats. We might also want our distribution to be non-uniform --
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for example, a Gaussian distribution
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*/
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/**
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`GKShuffledDistribution` is an anti-clustering distribution, which means it
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shapes the distribution of random numbers so that you are less
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likely to get repeats. This means it will go through every
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possible number before you see a repeat, which makes for a
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truly perfect distribution of numbers.
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*/
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let shuffledDistribution = GKShuffledDistribution.d6()
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for roll in 1...6 {
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print("Roll \(roll): \(shuffledDistribution.nextInt())")
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}
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let gaussianDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 20)
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var counts: [Int : Int] = [:]
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for _ in 1...100_000 {
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let result = gaussianDistribution.nextInt()
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if let currentCount = counts[result] {
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counts[result] = currentCount + 1
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} else {
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counts[result] = 1
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}
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}
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for number in 1...20 {
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print("\(number): \(counts[number]!)")
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}
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/**
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Random number generators consist of two components: A source (sometimes synonymous with "engine") and a distribution.
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The entropic output of the source/engine is mapped onto the distribution to produce a final value.
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This is important, because we can _seed_ engines -- give them specific starting point. When
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an engine is deterministic, using a common seed allows us to reproduce the same random output
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across systems and individual game runs.
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*/
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let twisterEngineA = GKMersenneTwisterRandomSource(seed: 42)
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let twisterEngineB = GKMersenneTwisterRandomSource(seed: 42)
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let options = [Int](0...200)
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let selectionA = twisterEngineA.arrayByShufflingObjects(in: options)[0..<6]
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let selectionB = twisterEngineB.arrayByShufflingObjects(in: options)[0..<6]
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print(selectionA)
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print(selectionB)
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//: [Next](@next)
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import UIKit
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import GameplayKit
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let sharedRandom = GKRandomSource.sharedRandom()
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print(sharedRandom.nextInt())
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print(sharedRandom.nextInt())
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print(sharedRandom.nextInt())
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print(sharedRandom.nextInt(upperBound: 20))
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print(sharedRandom.nextInt(upperBound: 20))
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print(sharedRandom.nextInt(upperBound: 20))
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print(sharedRandom.nextBool())
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print(sharedRandom.nextUniform())
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/**
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Using the system's built-in random number source is exactly what you want when you just need something simple.
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But the system's random number generator is not deterministic,
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which means you can't predict what numbers it will output because it
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always starts in a different state – and that makes it useless for synchronizing network games.
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*/
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/**
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Fortunately, GameplayKit offers three custom sources of random numbers,
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all of which are deterministic, and all of which can be
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serialized – i.e., written out to disk using something like NSCoding:
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1. `GKLinearCongruentialRandomSource`: Slightly higher performance than Arc4, but lower randomness
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2. `GKMersenneTwisterRandomSource`: High randomness, but slightly lower performance than Arc4
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3. `GKARC4RandomSource`: Goldilocks random source
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⚠️ While deterministic, none of these ar cryptographically secure
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*/
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let linearCongruential = GKLinearCongruentialRandomSource()
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print(linearCongruential.nextInt(upperBound: 20))
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let twister = GKMersenneTwisterRandomSource()
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print(twister.nextInt(upperBound: 20))
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let arc4 = GKARC4RandomSource()
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/**
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⚠️ Apple recommends you force flush its ARC4 random number generator before using it
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for anything important, otherwise it will generate sequences that can be
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guessed to begin with. Apple suggests dropping at least the first 769.
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*/
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arc4.dropValues(1024)
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print(arc4.nextInt(upperBound: 20))
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@ -0,0 +1,39 @@
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//: [Previous](@previous)
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import Foundation
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/// `arc4random` is the classic way to generate random numbers.
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/// It generates a number between 0 and 4,294,967,295, giving a range of 2^(32 - 1)
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print(arc4random())
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/// We can constrain this with a modulus
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print(arc4random() % 42)
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/// But to prevent [modulo bias](https://zuttobenkyou.wordpress.com/2012/10/18/generating-random-numbers-without-modulo-bias/), we can just pass our constraint as an argument
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print(arc4random_uniform(42))
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func randomBetween(min: Int, max: Int) -> Int {
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guard min < max else { return min }
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let randomFactor = Int(arc4random_uniform(UInt32((max - min) + 1)))
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return randomFactor + min
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}
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for i in 0..<10 {
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print(randomBetween(min: 4, max: 10 + (i * 10)))
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}
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/// So yeah... Swift's newer randomness methods are much nicer 😎
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print(Int.random(in: 100...1000))
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print(Double.random(in: 100...1000))
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print(Float.random(in: 100...1000))
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print(Bool.random())
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//: [Next](@next)
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@ -0,0 +1,8 @@
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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='6.0' target-platform='ios' executeOnSourceChanges='false'>
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<pages>
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<page name='Old School Randomness'/>
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<page name='GameplayKit Randomness'/>
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<page name='Distributions'/>
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</pages>
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</playground>
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@ -58,8 +58,8 @@
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| 32 | 📱<br>[Swift Searcher](/32-swift-searcher) | Dynamic Type, NSAttributedString, SFSafariViewController, SFSafariViewControllerDelegate, Core Spotlight, UIContentSizeCategoryDidChange, responding to the `CSSearchableItemActionType` activity during app startup to handle CoreSpotlight search hits | ✅ |
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| 33 | 📱<br>[Name That Tune](/33-cloudkit-guess-the-song) | All about CloudKit ☁️: loading and saving text data, loading and saving binary data, subscribing to CKRecord updates, delivering push notifications, CloudKit Dashboard and more; AVAudioRecorder; AVAudioSession; requestRecordPermission(); CKRecord; CKAsset; CKQueryOperation; NSPredicate; CKRecord.Reference; fetch(withRecordID:); save(); CKQuerySubscription; NSSortDescriptor | ✅ |
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| 34 | 🎮<br>[Four in a Row](/34-gamekit-four-in-a-row) | GameplayKit AI, GKGameModel, GKGameModelPlayer, GKGameModelUpdate, AI Heuristics, NSCopying, GKMinmaxStrategist | ✅ |
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| 35 | 🛠<br>[Random Numbers](/35-Random-Numbers) | Int.random(in:), Float.random(in:), Double.random(in:), CGFloat.random(in:), Bool.random(), arc4random(), GKRandomSource.sharedRandom(), GKLinearCongruentialRandomSource, GKMersenneTwisterRandomSource, GKARC4RandomSource, GKRandomDistribution, GKShuffledDistribution, GKGaussianDistribution, Fisher-Yates Algorithm, arrayByShufflingObjects(in:) | 🚧 |
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| 36 | 🎮<br>[Crashy Plane](/36-crashy-plane) | Composed Methods, Scale Modes, Parallax Scrolling, SpriteKit Physics, SKPhysicsContactDelegate, SKPhysicsBody, SKAudioNode, Managing Game State | 🔴 |
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| 35 | 🛠<br>[Random Numbers](/35-random-numbers) | Int.random(in:), Float.random(in:), Double.random(in:), CGFloat.random(in:), Bool.random(), arc4random(), GKRandomSource.sharedRandom(), GKLinearCongruentialRandomSource, GKMersenneTwisterRandomSource, GKARC4RandomSource, GKRandomDistribution, GKShuffledDistribution, GKGaussianDistribution, Fisher-Yates Algorithm, arrayByShufflingObjects(in:), the importance of being able to seed the source of randomness 🌱| ✅ |
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| 36 | 🎮<br>[Crashy Plane](/36-crashy-plane) | Composed Methods, Scale Modes, Parallax Scrolling, SpriteKit Physics, SKPhysicsContactDelegate, SKPhysicsBody, SKAudioNode, Managing Game State | 🚧 |
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| 37 | 🎮<br>[Psychic Tester](/37-psychic-tester) | WatchKit Extensions, 3D Touch, CAEmitterLayer, CAGradientLayer, @IBDesignable, @IBInspectable, transition(with:), WCSession, WKInterfaceLabel, WKInterfaceButton | 🔴 |
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| 38 | 🛠<br>[Github Commits (Core Data)](/38-githubcommits) | NSFetchRequest, NSManagedObject, NSPredicate, NSSortDescriptor, NSFetchedResultsController, ISO8601DateFormatter | 🔴 |
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| 39 | 🛠<br>[Unit testing with XCTest](/39-swift-unit-tests) | XCTest, `filter()`, Test-Driven Development, Functional Programming, XCTestCase, Setting a Baseline, NSCountedSet, XCUIApplication(), XCUIElementQuery, UI Test Recording | 🔴 |
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