约束newtype参数

Question

拥有以下自定义新类型：

newtype QueryM a = QueryM (Connection -> IO a) 

如何在限制Alternative拥有a实例的同时为其声明Alternative个实例？或者我可以吗？

我的意思是这样的：

instance (Alternative a) => Alternative (QueryM a) where

Answer 1

如果我在a添加参数，请在此处编译好：

import Control.Applicative

newtype QueryM a b = QueryM (Connection -> IO (a b))

type Connection = ()

instance Functor (QueryM a)
instance Applicative (QueryM a)

instance (Alternative a) => Alternative (QueryM a) where