Re: [Haskell-beginners] how to split a list

26 Mar 2018

      On Mon, Mar 26, 2018 at 08:11:44PM +0200, Francesco Ariis wrote:
...
There's the usual zip trick
λ> l = [1,2, 3, 4, 6, 7, 9, 10]
    λ> zipWith (-) l [1..]
    [0,0,0,0,1,1,2,2]
    λ> zip l it
    [(1,0),(2,0),(3,0),(4,0),(6,1),(7,1),(9,2),(10,2)]
To be more explicit:

    λ> :m +Data.List (groupBy)
    λ> :m +Data.Function (on)
    λ> l = [1,2, 3, 4, 6, 7, 9, 10]
    λ> map (map snd) $ groupBy ((==) `on` snd) $ zip l (zipWith (-) l [1..])
    [[0,0,0,0],[1,1],[2,2]]

Maybe with some lens or with a foldr you can end up with something shorter
than this (69 characters).