Merge pull request #155 from haskell/lehins/mkStdGen64

Add `mkStdGen64`.
haskell · Nov 27, 2023 · fdcc5d2 · fdcc5d2
2 parents 5e1d5bb + d60ef3d
commit fdcc5d2
Show file tree

Hide file tree

Showing 3 changed files with 17 additions and 3 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,6 +1,8 @@
 # 1.3.0
 
-* Add `uniformListRM`, `uniformList`, `uniformListR`, `uniforms` and `uniformRs`: [#154](https://github.com/haskell/random/pull/154)
+* Add `mkStdGen64`: [#155](https://github.com/haskell/random/pull/155)
+* Add `uniformListRM`, `uniformList`, `uniformListR`, `uniforms` and `uniformRs`:
+  [#154](https://github.com/haskell/random/pull/154)
 * Add compatibility with recently added `ByteArray` to `base`:
   [#153](https://github.com/haskell/random/pull/153)
   * Switch to using `ByteArray` for type class implementation instead of

diff --git a/src/System/Random.hs b/src/System/Random.hs
@@ -52,6 +52,7 @@ module System.Random
   -- ** Standard pseudo-random number generator
   , StdGen
   , mkStdGen
+  , mkStdGen64
   , initStdGen
 
   -- ** Global standard pseudo-random number generator
@@ -113,7 +114,7 @@ import qualified System.Random.SplitMix as SM
 --
 -- >>> :{
 -- let rolls :: RandomGen g => Int -> g -> [Word]
---     rolls n = take n . unfoldr (Just . uniformR (1, 6))
+--     rolls n = fst . uniformListR n (1, 6)
 --     pureGen = mkStdGen 137
 -- in
 --     rolls 10 pureGen :: [Word]
@@ -125,7 +126,7 @@ import qualified System.Random.SplitMix as SM
 --
 -- >>> :{
 -- let rollsM :: StatefulGen g m => Int -> g -> m [Word]
---     rollsM n = replicateM n . uniformRM (1, 6)
+--     rollsM n = uniformListRM n (1, 6)
 --     pureGen = mkStdGen 137
 -- in
 --     runStateGen_ pureGen (rollsM 10) :: [Word]

diff --git a/src/System/Random/Internal.hs b/src/System/Random/Internal.hs
@@ -37,6 +37,7 @@ module System.Random.Internal
   -- ** Standard pseudo-random number generator
   , StdGen(..)
   , mkStdGen
+  , mkStdGen64
   , theStdGen
 
   -- * Monadic adapters for pure pseudo-random number generators
@@ -882,6 +883,16 @@ instance RandomGen SM32.SMGen where
 mkStdGen :: Int -> StdGen
 mkStdGen = StdGen . SM.mkSMGen . fromIntegral
 
+-- | Constructs a 'StdGen' deterministically from a `Word64` seed.
+--
+-- The difference between `mkStdGen` is that `mkStdGen64` will work the same on 64-bit and
+-- 32-bit architectures, while the former can only use 32-bit of information for
+-- initializing the psuedo-random number generator on 32-bit operating systems
+--
+-- @since 1.3.0
+mkStdGen64 :: Word64 -> StdGen
+mkStdGen64 = StdGen . SM.mkSMGen
+
 -- | Global mutable veriable with `StdGen`
 theStdGen :: IORef StdGen
 theStdGen = unsafePerformIO $ SM.initSMGen >>= newIORef . StdGen