我有一个简单的类型类，用于表示一个实例的连续概率分布。我想尽可能地写出类型类和公式，以便例如可以在Float或Double之间进行适当选择。

无法编译：

class ContinuousDistribution d where
    ppf :: Floating a => d -> a -> a

data Uniform = Uniform
     { lowerBound :: Float,upperBound :: Float
     } deriving (Show)

instance ContinuousDistribution Uniform where
    ppf d q = (1.0 - q) * lowerBound d + q * upperBound d

生产

stats.hs:10:27: error:
    • Couldn't match expected type ‘a’ with actual type ‘Float’
      ‘a’ is a rigid type variable bound by
        the type signature for:
          ppf :: forall a. Floating a => Uniform -> a -> a
        at stats.hs:10:5
    • In the second argument of ‘(*)’,namely ‘lowerBound d’
      In the first argument of ‘(+)’,namely ‘(1.0 - q) * lowerBound d’
      In the expression: (1.0 - q) * lowerBound d + q * upperBound d
    • Relevant bindings include
        q :: a (bound at stats.hs:10:11)
        ppf :: Uniform -> a -> a (bound at stats.hs:10:5)
Failed,modules loaded: none.

在类型类声明中指定类型可以编译，但仅限于Float。

class ContinuousDistribution d where
    ppf :: d -> Float -> Float

data Uniform = Uniform
     { lowerBound :: Float,upperBound :: Float
     } deriving (Show)

instance ContinuousDistribution Uniform where
    ppf d q = (1.0 - q) * lowerBound d + q * upperBound d

修改类型类的规范方法是什么，以便我可以根据需要使用Float或Double？