gamma-0.7: src/Math/Gamma.hs-boot

module Math.Gamma where

class Floating a => Gamma a where
    -- |The gamma function:  gamma z == integral from 0 to infinity of
    -- @\t -> t**(z-1) * exp (negate t)@
    gamma :: a -> a
    gamma 0 = 0/0
    gamma z
        | z == abs z    = exp (lnGamma z)
        | otherwise     = pi / (sin (pi * z) * exp (lnGamma (1-z)))


    -- |Natural log of the gamma function
    lnGamma :: a -> a
    lnGamma z = log (gamma z)
    
    -- |Natural log of the factorial function
    lnFactorial :: Integral b => b -> a
    lnFactorial n = lnGamma (fromIntegral n+1)

instance Gamma Float where
instance Gamma Double where