I try to create a variable to get value random with drand48 () but in each run my variable take a same value . can anybody help me , (i want in each run my variable take different value) ???
let number = drand48 ()
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2Have read the documentation for `drand48`? You need to seed it. – rmaddy Oct 07 '16 at 18:35
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can you tell me about it ?? – scbas1000 Oct 07 '16 at 18:36
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1Not a direct answer to your question, but in many cases, `arc4random()` or `arc4random_uniform()` is a better choice. – Martin R Oct 07 '16 at 18:51
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drand48 creates a Pseudo-random number sequence. That is if it is not set to a different start point each time it will always produce the same numbers.
To fix this call srand48 beforehand to set a new start point for drand48
Eg
let time = UInt32(NSDate().timeIntervalSinceReferenceDate)
srand48(Int(time))
let number = drand48 ()
Here are the docs for drand48 and srand48
Edit: different way to seed to avoid the error, I'm not by a computer (on my phone) so may have to fix it later if it doesn't work
Olivier Wilkinson
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The `srand48` function seeds the pseudorandom number generator. – David Schwartz Oct 07 '16 at 18:40
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also i can run my code ** Cannot convert value of type 'Int' to expected argument type 'UnsafeMutablePointer
' (aka 'UnsafeMutablePointer – scbas1000 Oct 07 '16 at 18:40')** -
Exactly, I'll add the documentation for drand48 and its family functions to my answer – Olivier Wilkinson Oct 07 '16 at 18:41
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thanks , it works but a little note : you must change **srand48(time)** to **srand48(Int(time))** – scbas1000 Oct 07 '16 at 18:53
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