Hello, I would like to use the sqrt function on Fractional numbers. (mysqrt :: (Fractional a) => a->a) Half of the problem is solved by: Prelude> :t (realToFrac.sqrt) (realToFrac.sqrt) :: (Fractional b, Real a, Floating a) => a -> b For the other half I tried: Prelude> :t (realToFrac.sqrt.realToFrac) (realToFrac.sqrt.realToFrac) :: (Fractional b, Real a) => a -> b Prelude> :t (realToFrac.sqrt.fromRational.toRational) (realToFrac.sqrt.fromRational.toRational) :: (Fractional b, Real a) => a -> b Prelude> :t (realToFrac.sqrt.realToFrac.fromRational.toRational) (realToFrac.sqrt.realToFrac.fromRational.toRational) :: (Fractional b, Real a) => a -> b I have to admit that I do not fully understand the Haskell numerical tower... Now I'm using the Newton method: mysqrt :: (Fractional a) => a -> a mysqrt x = (iterate (\y -> (x / y + y) / 2.0 ) 1.0) !!2000 But I want a faster solution. (Not by replacing 2000 with 100... :) Zoltan