How to tell haskell that 'a' is '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
Hi, Use ScopedTypeVariables and forall: {-# LANGUAGE ScopedTypeVariables #-} skips :: forall a. [a] -> [[a]] skips xs = go 1 [] where go :: Int -> [[a]] -> [[a]] * ...* Sylvain On 14/11/2016 03:15, Lai Boon Hui wrote:
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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participants (2)
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Lai Boon Hui -
Sylvain Henry