使用Typeable在运行时部分应用功能（任何时间类型匹配）
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通用编程时间！
如果我有一个功能：
f :: a1 -> a2 -> a3 -> ... -> an
v :: aX -- where 1 <= x < n
f
v
f
v
g
g :: (a1 -> a2 -> a3 -> a4 -> a5) -> a3 -> (a1 -> a2 -> a4 -> a5)
g f v = \\x y z -> f x y v z
typeRepArgs
v
f
f
import Data.Typeable
data Box = forall a. Box (TyRep, a)
mkBox :: Typeable a => a -> Box
mkBox = (typeOf a, a)
g :: Box -> Box -> [Box]
g (Box (ft,f)) (Box (vt,v)) =
let argNums = [n | n <- [1..nrArgs], isNthArg n vt ft]
in map (mkBox . magicApplyFunction f v) argNums
isNthArg :: Int -> TyRep -> TyRep -> Bool
isNthArg n arg func = Just arg == lookup n (zip [1..] (typeRepArgs func))
nrArgs :: TyRep -> Int
nrArgs = (\\x -> x - 1) . length . typeRepArgs
buildFunc :: f -> x -> Int -> g
buildFunc f x 0 = unsafeCoerce f x
buildFunc f x i =
let !res = \\y -> (buildFunc (unsafeCoerce f y) x (i-1))
in unsafeCoerce res
没有找到相关结果
已邀请:
2 个回复
仇聘发栖
和完成此操作。 ѭ17和ѭ18的来源应提供关键要素：dynApply :: Dynamic -> Dynamic -> Maybe Dynamic dynApply (Dynamic t1 f) (Dynamic t2 x) = case funResultTy t1 t2 of Just t3 -> Just (Dynamic t3 ((unsafeCoerce f) x)) Nothing -> Nothing funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep funResultTy trFun trArg = case splitTyConApp trFun of (tc, [t1,t2]) | tc == funTc && t1 == trArg -> Just t2 _ -> Nothing将在框中寻找第一个匹配的TypeRep，并替换值的。然后，您可能会得到一个ѭ23，给定一个ѭ24which，所有参数已被魔术应用，实际上执行调用以产生结果动态结果。桔适丛
{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, TypeFamilies, UndecidableInstances, IncoherentInstances, ScopedTypeVariables #-} class Magical a b c where apply :: a -> b -> c instance (AreEqual a c e, Magical\' e (a -> b) c r) => Magical (a -> b) c r where apply f a = apply\' (undefined :: e) f a class Magical\' e a b c where apply\' :: e -> a -> b -> c instance (r ~ b) => Magical\' True (a -> b) a r where apply\' _ f a = f a instance (Magical b c d, r ~ (a -> d)) => Magical\' False (a -> b) c r where apply\' _ f c = \\a -> apply (f a) c data True data False class AreEqual a b r instance (r ~ True) => AreEqual a a r instance (r ~ False) => AreEqual a b r test :: Int -> Char -> Bool test i c = True t1 = apply test (5::Int) t2 = apply test \'c\'