open number

//A class that defines our overloadable function
class Exponent a where
  (^) a->a->_

//Implementation for integers
instance Exponent Int where
  _ ^ 0           =  1
  x ^ n | n > 0   =  f x (n - 1) x
        |else = fail "Negative exponent"
    where f _ 0 y = y
          f a d y = g a d
            where g b i | even i  = g (b * b) (i `quot` 2)
                        | else = f b (i - 1) (b * y)

//Implementation for floats
instance Exponent Single where
  x ^ n | n < 0.001 = 1
        | n > 0 =  f x (n - 1) x
        | else = fail "Negative exponent"
    where f a d y
            | d < 0.001 = y
            | else = g a d
            where g b i | even i  = g (b * b) (i / 2)
                        | else = f b (i - 1) (b * y)

(12 ^ 4, 12.34 ^ 4.04)