Hi,

Use ScopedTypeVariables and forall:

{-# LANGUAGE ScopedTypeVariables #-}

skips :: forall a. [a] -> [[a]]
skips xs = go 1 [] where
   go :: Int -> [[a]] -> [[a]]
   ...

Hi all,

skips :: [a] -> [[a]]

skips xs = go 1 [] where

  go :: Int -> [[a]] -> [[a]] -- Compiles if i remove this line

  go n acc

    | n > (length xs) = acc

    | n == 1 = xs : (go (n+1) acc)

    | n < 1 = []

    | otherwise = (everyN n xs) : (go (n+1) acc)

everyN :: Int -> [a] -> [a]

everyN n xs =

  case (drop (n-1) xs) of

    y:ys -> y : (everyN n ys)

    [] -> []

How can i tell haskell compiler that a is the sub program if the same as a in the main program?

--

Best Regards,

Boon Hui

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