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Convert a list of things into a list of sublists

I want to write a function that converts a list of things into a list of sublists, each containing elements of the same value, which when concatenated together give the same list.

So runs [1,2,2,1,3,3,3,2,2,1,1,4] becomes [[1],[2,2],[1],[3,3,3],[2,2],[1,1],[4]]

How do I solve this problem in Haskell?

Solution

  • This function already exists, this is group :: Eq a => [a] -> [[a]]:

    Prelude> import Data.List(group)
Prelude Data.List> group [1,2,2,1,3,3,3,2,2,1,1,4]
[[1],[2,2],[1],[3,3,3],[2,2],[1,1],[4]]