Haskell: Change a list of 100 numbers to 10 lists of 10 numbers?

Question

In Haskell, how does one change a list of x numbers into n lists of n numbers?

The first sublist would have numbers first to tenth, second list 11th to 20th...

myFunction :: [Int] -> [[Int]]

András Kovács · Accepted Answer · 2014-06-16T20:32:20.347

5

There is the chunksOf function in Data.List.Split:

chunksOf 2 [0, 1, 2, 3] -- [[0, 1], [2, 3]]

Alternatively, we already have splitAt in prelude, with which chunksOf can be implemented with ease:

chunksOf :: Int -> [a] -> [[a]]
chunksOf n [] = []
chunksOf n xs = let (as, bs) = splitAt n xs in as : chunksOf n bs

edited Jun 16 '14 at 20:32

answered Jun 16 '14 at 20:26

András Kovács

note that in older versions of ghc you have to 'cabal install split' (i think before 7.6) – epsilonhalbe Jun 16 '14 at 20:52
Why oh why isn't an equivalent in Prelude? I don't want o depend on the split package if I'm writing something quick & small. – Alex Feb 14 '16 at 16:58

score 3 · Answer 2 · answered Jun 17 '14 at 07:30

3

Might be a little simpler to read with take and drop and requires no libraries.

chunksOf :: Int -> [a] -> [[a]]
chunksOf _ [] = []
chunksOf n xs = take n xs : chunksOf n (drop n xs)

answered Jun 17 '14 at 07:30

mmachenry

2 Answers2