(**) Drop every N'th element from a list.
dropEvery :: [a] -> Int -> [a] dropEvery  _ =  dropEvery (x:xs) n = dropEvery' (x:xs) n 1 where dropEvery' (x:xs) n i = (if (n `divides` i) then  else [x]) ++ (dropEvery' xs n (i+1)) dropEvery'  _ _ =  divides x y = y `mod` x == 0
An alternative iterative solution:
dropEvery :: [a] -> Int -> [a] dropEvery list count = helper list count count where helper  _ _ =  helper (x:xs) count 1 = helper xs count count helper (x:xs) count n = x : (helper xs count (n - 1))
Yet another iterative solution which divides lists using Prelude:
dropEvery :: [a] -> Int -> [a] dropEvery  _ =  dropEvery list count = (take (count-1) list) ++ dropEvery (drop count list) count
A similar approach using guards:
dropEvery :: [a] -> Int -> [a] dropEvery xs n | length xs < n = xs | otherwise = take (n-1) xs ++ dropEvery (drop n xs) n
dropEvery = flip $ \n -> map snd . filter ((n/=) . fst) . zip (cycle [1..n])
Using zip and list comprehensions
dropEvery :: [a] -> Int -> [a] dropEvery xs n = [ i | (i,c) <- ( zip xs [1,2..]), (mod c n) /= 0]
A more complicated approach which first divides the input list into sublists that do not contain the nth element, and then concatenates the sublists to a result list (if not apparent: the author's a novice):
dropEvery :: [a] -> Int -> [a] dropEvery  _ =  dropEvery xs n = concat (split n xs) where split _  =  split n xs = fst splitted : split n ((safetail . snd) splitted) where splitted = splitAt (n-1) xs safetail xs | null xs =  | otherwise = tail xs
First thing that came to mind:
dropEvery xs n = map fst $ filter (\(x,i) -> i `mod` n /= 0) $ zip xs [1..]
The filter function can be simplified.