System.Random: StdGen's genRange doesn't match its next
> g <- getStdGen
> length $ filter (<0) $ take (10^6) $ unfoldr (Just . next) g
0
> genRange g
(-2147483648,2147483647)Apparently, StdGen's next only returns non-negative values.
Also, StdGen doesn't override de default method genRange. However, the System.Random docs (http://haskell.org/ghc/docs/latest/html/libraries/base/System-Random.html#v%3Anext) promise:
The next operation returns an Int that is uniformly distributed in the range returned by genRange (including both end points), and a new generator.
Thus, StdGen's next violates the uniform distribution requirement.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 6.4.2 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | libraries/base |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | Unknown |
| Architecture | Unknown |