Question

这是我遇到的一个奇怪的问题（在VSCode中）。我有一个长的多行文本，该文本既不会从编辑器复制到python终端（Ctrl + V），也不会响应Shift-Enter快捷方式。例如这段文字

{-# LANGUAGE GADTs #-}

import qualified Data.List            as L
import qualified Data.Set             as S
import qualified Data.Functor         as F
import qualified Control.Applicative  as A
import Control.Monad


dlbind xs f = L.nub $ xs >>= f

data DL a where
  Prim   :: Eq a => [a] -> DL a
  Return :: a -> DL a
  Bind   :: DL b -> (b -> DL a) -> DL a
--  Fail   :: DL a  -- could be add to clear failure chains

run :: Eq a => DL a -> [a]
run (Prim xs)      = xs
run (Return x)     = [x]
run b@(Bind _ _)   =
  case foldChain b of 
    (Bind (Prim xs) f)   -> L.nub $ concatMap (run . f) xs
    (Bind (Return a) f)  -> run (f a)
    (Bind (Bind ma f) g) -> run (Bind ma (\a -> Bind (f a) g))

-- fold a chain ((( ... >>= f) >>= g) >>= h
foldChain :: DL u -> DL u  
foldChain (Bind b2 g) = stepChain $ Bind (foldChain b2) g 
foldChain dxs         = dxs

-- simplify (Prim _ >>= f) >>= g 
--   if  (f x = Prim _)
--   then reduce to (Prim _ >>= g)
--   else preserve  (Prim _ >>= f) >>= g 
stepChain :: DL u -> DL u
stepChain b@(Bind (Bind (Prim xs) f) g) =
  let dys = map f xs
      pms = [Prim ys   | Prim   ys <- dys]
      ret = [Return ys | Return ys <- dys]
      bnd = [Bind ys f | Bind ys f <- dys]
  in case (pms, ret, bnd) of
       -- ([],[],[]) -> Fail -- could clear failure
       (dxs@(Prim ys:_),[],[]) -> let Prim xs = joinPrims dxs (Prim $ mkEmpty ys)
                                  in Bind (Prim $ L.nub xs) g       
       _  -> b
stepChain dxs = dxs

-- empty list with type via proxy  
mkEmpty :: proxy a -> [a]
mkEmpty proxy = []

-- concatenate Prims in on Prim
joinPrims [] dys = dys 
joinPrims (Prim zs : dzs) dys = let Prim xs = joinPrims dzs dys in Prim (zs ++ xs)  

instance (Ord a) => Eq (DL a) where
  dxs == dys = run dxs == run dys

instance (Ord a) => Ord (DL a) where
  compare dxs dys = compare (run dxs) (run dys)

instance (Show a, Eq a) => Show (DL a) where
  show = show . run    

instance F.Functor DL where
  fmap  = liftM 

instance A.Applicative DL where
  pure  = return
  (<*>) = ap

instance Monad DL where
  return = Return
  (>>=)  = Bind


-- cheating here, Prim is needed for efficiency 
return' x = Prim [x]

s =  [1,2,3,4] >>= (\x ->  [x `mod` 2, x `mod` 3])   
t = (Prim [1,2,3,4]) >>= (\x -> Prim [x `mod` 2, x `mod` 3]) 
r' = ((Prim [1..1000]) >>= (\x -> return' 1)) >>= (\x -> Prim [1..1000])

不会响应Shift + Enter命令，但是如果减少四到三行，该命令将起作用。我在IDLE上测试了该功能，但是我想VSCOde不能正常工作，请您帮我吗？

无法在VSCode中运行较长的python文本

0 个答案: