#8899: StdGen does not generate 0 ------------------------------------+------------------------------------- Reporter: novadenizen | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/random | Version: 7.9 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- `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^''. {{{#!haskell 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 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8899 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler