arc4random

I need to generate 8 random integers, but they need to be unique, aka not repeated. For example, I want 8 numbers within the range 1 to 8. I've seen arc4random but I'm not sure how to make them unique ? Solution -(NSMutableArray *)getRandomInts:(int)amount from:(int)fromInt to:(int)toInt { if ((toInt - fromInt) +1 < amount) { return nil; } NSMutableArray *uniqueNumbers = [[[NSMutableArray alloc] init] autorelease]; int r; while ([uniqueNumbers count] < amount) { r = (arc4random() % toInt) + fromInt; if (![uniqueNumbers containsObject:[NSNumber numberWithInt:r]]) { [uniqueNumbers addObject:

So, with my current project, I need to work with 64-bit integers and I need to grab random numbers between ranges up to 100 billion. arc4random()/arc4random_uniform() only works with unsigned 32-bit integers. I can probably fudge it a little because my min/max range for every call will likely not exceed 2 billion, but I'd like to futureproof myself in case I decide that, well, I do need a broader range. Any advice? Update: As of Swift 4.2 (distributed with Xcode 10.1) there is a unified random API in the Swift standard library, see SE 0202 Random Unification . You can simply call UInt64.random

According to this documentation , arc4random_uniform() is recommended over constructions like arc4random() % upper_bound as it avoids "modulo bias" when the upper bound is not a power of two. How bad is the bias? For example if I generate random numbers with an upper bound of 6, what's the difference between using arc4random with % and arc4random_uniform() ? arc4random() returns an unsigned 32-bit integer, meaning the values are between 0 and 2^32-1 = 4 294 967 295. Now, the bias results from the fact that the multiple subintervals created with modulo are not fitting exactly into the random

I need to generate a random number. It appears the arc4random function no longer exists as well as the arc4random_uniform function. The options I have are arc4random_stir() , arc4random_buf(UnsafeMutablePointer<Void>, Int) , and arc4random_addrandom(UnsafeMutablePointer<UInt8>, Int32) . I can't find any docs on the functions and no comments in the header files give hints. ===== Swift 4.2 / Xcode 10 ===== let randomIntFrom0To10 = Int.random(in: 1..<10) let randomFloat = Float.random(in: 0..<1) // if you want to get a random element in an array let greetings = ["hey", "hi", "hello", "hola"]

In Swift, I'm trying to get a random float between 0 and 1 but I can't seem to get the type conversions to work. func randomCGFloat() -> CGFloat { return CGFloat(arc4random()) / UINT32_MAX } I'm getting a 'CGFloat' is not convertible to 'UInt8' error Running Xcode 6. Try initializing the divisor as a float as well, a la: CGFloat(Float(arc4random()) / Float(UINT32_MAX)) This is extension for random numbers of Int, Double, Float, CGFloat Swift 3 & 4 syntax import Foundation import CoreGraphics // MARK: Int Extension public extension Int { /// Returns a random Int point number between 0 and Int

I'm trying to generate a random number that's between 0 and 1. I keep reading about arc4random() , but there isn't any information about getting a float from it. How do I do this? Vladimir Random value in [0, 1[ (including 0, excluding 1): double val = ((double)arc4random() / UINT32_MAX); A bit more details here . Actual range is [0, 0.999999999767169356] , as upper bound is (double)0xFFFFFFFF / 0x100000000. // Seed (only once) srand48(time(0)); double x = drand48(); // Swift version // Seed (only once) srand48(Int(Date().timeIntervalSince1970)) let x = drand48() The drand48() and erand48()