Update cabal + add wrapper over MWC

Statistics/Distribution/Poisson.hs

@@ -31,18 +31,21 @@
 import Data.Binary          (Binary(..))
 import Data.Data            (Data, Typeable)
 import GHC.Generics         (Generic)
+
+import qualified System.Random.MWC.Distributions as MWC
+
 import Numeric.SpecFunctions (incompleteGamma,logFactorial)
 import Numeric.MathFunctions.Constants (m_neg_inf)
 
+
 import qualified Statistics.Distribution as D
 import qualified Statistics.Distribution.Poisson.Internal as I
 import Statistics.Internal
 
 
-
 newtype PoissonDistribution = PD {
       poissonLambda :: Double
     } deriving (Eq, Typeable, Data, Generic)
 
 instance Show PoissonDistribution where
   showsPrec i (PD l) = defaultShow1 "poisson" l i
@@ -93,6 +96,14 @@
 instance D.MaybeEntropy PoissonDistribution where
   maybeEntropy = Just . D.entropy
 
+-- | @since 0.16.5.0
+instance D.DiscreteGen PoissonDistribution where
+  genDiscreteVar (PD lambda) = MWC.poisson lambda
+
+-- | @since 0.16.5.0
+instance D.ContGen PoissonDistribution where
+  genContVar (PD lambda) gen = fromIntegral <$> MWC.poisson lambda gen
+
 -- | Create Poisson distribution.
 poisson :: Double -> PoissonDistribution
 poisson l = maybe (error $ errMsg l) id $ poissonE l

changelog.md

@@ -1,3 +1,8 @@
+## Changes in 0.16.5.0 [2026.01.09]
+
+ * `ContGen` and `DiscreteGen` instances for `Poisson` distributions are added.
+
+
 ## Changes in 0.16.4.0 [2025.10.23]
 
  * Bartlett's test (`Statistics.Test.Bartlett`) and Levene's test

statistics.cabal

@@ -2,7 +2,7 @@ cabal-version:  3.0
 build-type:     Simple
 
 name:           statistics
-version:        0.16.4.0
+version:        0.16.5.0
 synopsis:       A library of statistical types, data, and functions
 description:
   This library provides a number of common functions and types useful
@@ -128,7 +128,7 @@ library
   build-depends: base                    >= 4.9 && < 5
                  --
                , math-functions          >= 0.3.4.1
-               , mwc-random              >= 0.15.0.0
+               , mwc-random              >= 0.15.3.0
                , random                  >= 1.2
                  --
                , aeson                   >= 0.6.0.0