看看Type是ghci的实例的哪个Typeclass? [英] See which Typeclasses the Type is an instance of in ghci?

问题描述

是否可以查看该类型实现的类型类?像这样:

Is it possible to see which typeclasses the type implements? Something like:

>:typeclasses Int
[Num, etc...]

推荐答案

使用:info命令.

Prelude> :info Int
data Int = GHC.Types.I# GHC.Prim.Int#   -- Defined in GHC.Types
instance Bounded Int -- Defined in GHC.Enum
instance Enum Int -- Defined in GHC.Enum
instance Eq Int -- Defined in GHC.Base
instance Integral Int -- Defined in GHC.Real
instance Num Int -- Defined in GHC.Num
instance Ord Int -- Defined in GHC.Base
instance Read Int -- Defined in GHC.Read
instance Real Int -- Defined in GHC.Real
instance Show Int -- Defined in GHC.Show

自然地，此列表取决于当前导入的模块.

Naturally this list depends on the modules that are currently imported.

Prelude> :info (->)
data (->) a b   -- Defined in GHC.Prim
Prelude> :m +Control.Monad.Instances
Prelude Control.Monad.Instances> :info (->)
data (->) a b   -- Defined in GHC.Prim
instance Monad ((->) r) -- Defined in Control.Monad.Instances
instance Functor ((->) r) -- Defined in Control.Monad.Instances

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