StdGen does not generate 0

genRange for StdGen returns (0,2147483562). However, as far as I can tell, StdGen doesn't generate 0.

This code performs 200 billion iterations of next on a StdGen. I ran it and it output Nothing. The probability that no 0 was generated by chance is approximately e^-200/2.147^ =~ 10^-40^.

` import System.Random import Data.Int

find0 :: StdGen -> Int64 -> Maybe Int64 find0 g0 n0 = aux g0 n0 where aux _ 0 = Nothing aux g r = let (v,g') = next g in if v == 0 then Just (n0 - r + 1) else aux g' (r-1)

main :: IO () main = print $ find0 (mkStdGen 1234) 200000000000 `

Trac metadata

Trac field	Value
Version	7.9
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/random
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