1

有谁知道如何创建 Data.Derive 实例生成器的分步教程？似乎有大量关于如何使用现有派生实例生成器的文档。

对于那些不熟悉 Data.Derive 的人（或者如果我只是特别不清楚），这就是我想要做的。给定一个简单的 newtype 示例，例如，

newtype WrapperT  α = WrapperT (StateT Integer  α)
    deriving (Applicative, Functor, Monad)

instance HzMonadBase  => HzMonadBase (WrapperT ) where
    data ExprTyp (WrapperT ) α = WrapperTE (ExprTyp (StateT Integer ) α)

我想生成所有这些实例（和约束数据系列）。它们几乎由字符串“WrapperT”、“WrapperTE”和“StateT Integer α”参数化。

data instance Constraints (ExprTyp (WrapperT )) α =
    (Suitable (ExprTyp ) α) => WrapperT_Constr
instance (Suitable (ExprTyp ) α) => Suitable (ExprTyp (WrapperT )) α where
    constraints = WrapperT_Constr

instance HzMonadBase  => HzExprTrans (ExprTyp (WrapperT )) where
    type PrimExpr (ExprTyp (WrapperT )) = ExprTyp (StateT Integer )
    e_lift = fmap WrapperTE
    e_lower = fmap (\(WrapperTE x) -> x)
    e_lower_suitably x@(ExprT v) f =
        withConstraintsOf v $ \WrapperT_Constr -> f (e_lower x)

instance HzMonadBase  => BinaryCmpExpr (ExprTyp (WrapperT ))
instance HzMonadBase  => BinaryOpExpr (ExprTyp (WrapperT ))
instance HzMonadBase  => SketchConstrExpr (ExprTyp (WrapperT ))
instance HzMonadBase  => Arithmetic (ExprTyp (WrapperT ))
instance HzMonadBase  => VariablesExpr (ExprTyp (WrapperT ))

instance HzMonadBase  => HzMonadTrans (WrapperT ) where
    type BaseMonad (WrapperT ) = StateT Integer 
    lift = WrapperT
instance HzMonadBase  => HzMonadUnliftTrans (WrapperT ) where
    unlift (WrapperT x) = x
4

0 回答 0