module Data.Random.Distribution.Triangular where
import Data.Random.RVar
import Data.Random.Distribution
import Data.Random.Distribution.Uniform
data Triangular a = Triangular
{ triLower :: a
, triMid :: a
, triUpper :: a
} deriving (Eq, Show)
realFloatTriangular :: (Floating a, Ord a, Distribution StdUniform a) => a -> a -> a -> RVar a
realFloatTriangular a b c
| a <= b && b <= c
= do
let p = (cb)/(ca)
u <- stdUniform
let d | u >= p = a
| otherwise = c
x | u >= p = (u p) / (1 p)
| otherwise = u / p
return (b ((1 sqrt x) * (bd)))
realFloatTriangularCDF :: RealFrac a => a -> a -> a -> a -> Double
realFloatTriangularCDF a b c x
| x < a
= 0
| x <= b
= realToFrac ((x a) ^ 2 / ((c a) * (b a)))
| x <= c
= realToFrac (1 (c x) ^ 2 / ((c a) * (c b)))
| otherwise
= 1
instance (RealFloat a, Ord a, Distribution StdUniform a) => Distribution Triangular a where
rvar (Triangular a b c) = realFloatTriangular a b c
instance (RealFrac a, Distribution Triangular a) => CDF Triangular a where
cdf (Triangular a b c) = realFloatTriangularCDF a b c