Randomisation of Games in Swift

Question

I've been doing code samples in SpriteKit Game Programming in Swift 2, in this Ray Wenderlich tutorial. This tutorial explains other of the game functionality very comprehensively, like the spawning of monsters, instantiation of the SKNodes, to the point of already including verbose instructions through the comments in the Sample Project. However, the use of the random() function that I cannot really comprehend.

  func random() -> Float {
    return CGFloat(Float(arc4random()) / 0xFFFFFFFF)
  }

  func random(min min: Float, max: Float) -> Float {
    return random() * (max - min) + min
  }

First of all, is this merely an override of the random() function right? Isn't like the random() function returns half of the arc4random()? And then why do have to divide it by 0xFFFFFFFF? What does that accomplish? And is the difference of the first and second function just the range and more randomisation?

the SECOND one is just an override that gives you a random between the given minimum and maximum you call it with. — Fattie, Dec 21 '15 at 02:03
i think the first is out of date, BTW. http://stackoverflow.com/a/32866619/294884 — Fattie, Dec 21 '15 at 02:05
So you're saying the first and second functions are not overrides of the random() function in UIKit? — Programming_Duders, Dec 21 '15 at 02:05
i think UIKit's "random()" returns an int. the top one returns a float, so it's a different signature. the bottom one has two args, so it's a different signature. You probably wouldn't really describe that as an "override" these days. — Fattie, Dec 21 '15 at 02:33
@Programming_Duders CGFloat it is not the same as Float. Your random method wouldn't even compile btw — Leo Dabus, Dec 21 '15 at 03:14

score 0 · Accepted Answer · answered Dec 21 '15 at 02:13

0

From the documentation of arc4random:

The arc4random() function returns pseudo-random numbers in the range of 0 to (2**32)-1

The first section of code in your question is the definition of a function random() that return a float pseudo-random number between 0 and 1.

This is obtained dividing the pseudo-random value for the maximum possible valued (0xFFFFFFFF is 2^32-1).

The second is an override of the previous one, that convert the range to your input one.

answered Dec 21 '15 at 02:13

AleFranz

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But what does it do when you call Float(arc4random()) / 0xFFFFFFFF? – Programming_Duders Dec 21 '15 at 02:22
As I said, it's dividing buy the maximum possible value, so it "converts" the value which is between 0 to 2^32-1 to a value between 0 and 1 – AleFranz Dec 21 '15 at 02:24
Oh, I get it Sir Ale :) – Programming_Duders Dec 21 '15 at 02:37
Sorry, I didn't mean to sound rude! :) – AleFranz Dec 21 '15 at 02:49
I wasn't offended :) Tysm – Programming_Duders Dec 21 '15 at 03:23
But one last question, why does there have to be a "min min" – Programming_Duders Dec 21 '15 at 03:32
@Programming_Duders this makes it required to be specified when calling the method otherwise you would call it random(0, max: 1) instead of random(min: 0, max: 1) – Leo Dabus Dec 21 '15 at 04:41

Randomisation of Games in Swift

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