I know Bulat will be terribly disappointed by my suggestion to make an addition to Data.List ;) but I mentioned the following couple of functions on #haskell and got some positive response that they were things other people ended up writing all the time as well, so I decided I'd propose them here as additions to Data.List and see what kind of reaction I got: -- | The 'select' function takes a list and produces a list of pairs -- consisting of an element of the list together with a list of the -- remaining elements. select :: [a] -> [(a,[a])] select [] = [] select (x:xs) = (x,xs) : [(y,x:ys) | (y,ys) <- select xs] -- | The 'selectSplit' function takes a list and produces a list of -- triples consisting of a prefix of the list, the element after it, -- and the remainder of the list. selectSplit :: [a] -> [([a],a,[a])] selectSplit [] = [] selectSplit (x:xs) = ([],x,xs) : [(x:lys,y,rys) | (lys,y,rys) <- selectSplit xs] These tend to be very handy in the list monad. The names are off the top of my head. Logan Capaldo also suggested 'pick' for the first, which is a name that I've used as well. Faxathisia mentioned that it's called 'select' in Prolog as well. As a side note, the state transformer makes it relatively easy to pick n elements using this: pick n = runStateT . replicateM n . StateT $ select (Showing that select is secretly an operation in a state transformed list monad, where the state is a list of elements.) If the order of the pairs in the MTL is fixed in the future in order to better reflect the available instances of Functor/etc., at that point we may want to consider flipping the pairs in the result of select to match. - Cale