更新时间:2023-11-05 11:30:04
Nathan Howell修改的要点: https ://gist.github.com/NathanHowell/6201625 :
Adapting this gist by Nathan Howell: https://gist.github.com/NathanHowell/6201625 :
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleContexts #-}
import GHC.Generics
constrName :: (HasConstructor (Rep a), Generic a)=> a -> String
constrName = genericConstrName . from
class HasConstructor (f :: * -> *) where
genericConstrName :: f x -> String
instance HasConstructor f => HasConstructor (D1 c f) where
genericConstrName (M1 x) = genericConstrName x
instance (HasConstructor x, HasConstructor y) => HasConstructor (x :+: y) where
genericConstrName (L1 l) = genericConstrName l
genericConstrName (R1 r) = genericConstrName r
instance Constructor c => HasConstructor (C1 c f) where
genericConstrName x = conName x
--------------
data Foo = Bar Int | Baz Float deriving Generic
newtype X = X Char deriving Generic
data Y = Y deriving Generic
我们可以做到:
*Main> constrName (Bar 1)
"Bar"
*Main> constrName $ X 'a'
"X"
*Main> constrName Y
"Y"