module Data.Random.Distribution.Beta where
import Data.Random.Internal.TH
import Data.Random.RVar
import Data.Random.Distribution
import Data.Random.Distribution.Gamma
import Data.Random.Distribution.Uniform
fractionalBeta :: (Fractional a, Distribution Gamma a, Distribution StdUniform a) => a -> a -> RVar a
fractionalBeta 1 1 = stdUniform
fractionalBeta a b = do
x <- gamma a 1
y <- gamma b 1
return (x / (x + y))
beta :: Distribution Beta a => a -> a -> RVar a
beta a b = rvar (Beta a b)
data Beta a = Beta a a
$( replicateInstances ''Float realFloatTypes [d|
instance Distribution Beta Float
where rvar (Beta a b) = fractionalBeta a b
|])