Ways to pack (adjacent) elements of a list into 2-tuples

Question

I was wondering if there would be a concise/one-liner way to do the following:

pack :: [a] -> [(a, a)]
pack []       = []
pack [_]      = []
pack (x:y:xs) = (         


        

Answer 1

Another one-liner using LambdaCase and Data.List.unfoldr:

pack = unfoldr $ \case (x:y:zs) -> Just ((x,y),zs); _ -> Nothing

Something I want occasionally is splits -

splits :: Int -> [a] -> [[a]]
splits n = unfoldr $ \case [] -> Nothing ; xs -> Just $ splitAt n xs

And given that, pack becomes:

pack xs = [ (a,b) | [a,b] <- splits 2 xs ]